|
Economic and Technical Analysis of
Fertilizer Innovations and Resource Use
In This Same Series:
Methodological Procedures in the
Economic Analysis of Fertilizer Use Dlata
E. L. Baum, Earl 0. Heady, and John Blackmore, Editors (1 956)
Economic and Technical Analysis of
Fertilizer Innovations and
Resource Use
E. L. BAUM
Chief, Agricultural Economics Branch, Tennessee Valley Authority
EARL 0. HEADY Professor of Economics, Iowa State College Economic Consultant, Tennessee Valley Authority Edited by JOHN T. PESEK
Associate Professor of Agronomy, Iowa State College
CLIFFORD 0. HILDRETH Professor of Agricultural Economics, Michigan State University Economic and Statistical Consultant, Tennessee Valley Authority
THE IOWA STATE COLLEGE PRESS - Ames, Iowa, U.S.A.
0 1957 by The Iowa State College Press.
All rights reserved.
Library of Congress Catalog Card Number: 57-7851
Foreword
ESEARCH oriented toward problems in the field of the economics
of fertilizer use is expanding rapidly. Coupled with this expansion is a conscious effort to improve and develop more efficient experimental designs and analytical tools. Fertilizer economics research is also being broadened to include fertilizer production, mixing and plant location economics, pricing and distribution, and the role of fertilizer in over-all farm planning.
In line with TVA's national responsibility to encourage the production, distribution, and use of high analysis-low cost fertilizers, a series of economic studies is being supported in representative areas of the United States. Research results, new theories, and techniques are presented in a seminar held annually for the cooperators in TVA's agricultural economics research program. This book contains many of the reports and papers presented at the latest of these seminars, which was held in Knoxville, Tennessee, March 27-30, 1956.
The scope of the 1956 seminar was quite broad, emphasizing recent thoughts on the numerous economic aspects of fertilizer, the fertilizer industry, and fertilizer relative to the over-all economy. These chapters appraise fertilizer problems which range from the minute considerations of microanalytical technique to the broader policy implications of increased fertilizer use.
The development and the significant increased use of improved chemical fertilizers represent a major innovation in American agriculture since World War II. The contributions in this book represent the most recent thinking and the latest research findings relative to many aspects of fertilizer in the American economy. The book presents new methodological techniques, which provide for more efficient handling of many fertilizer research problems than have been possible previously.
LELAND G. ALLBAUGH, Director Division of Agricultural Relations
Tennessee Valley Authority
Knoxville, Tennessee
October, 1956
N the interest of stimulating further study and the promotion of
greater integration of research and related educational efforts in
fertilizer development, distribution, use, and the economic implications of technological innovations in agriculture, such as newly developed high analysis fertilizers, TVA conducted a seminar on these matters in Knoxville, Tennessee, March 27-30, 1956. The seminar sessions were conducted under five closely related subject matter categories. They were: (a) research in agronomic and economic efficiency in rate of application, nutrient ratios, and farm use of fertilizers, (b) physical and economic aspects of water solubility of fertilizers, (c) an examination of liquid fertilizers, and some related marketing problems, (d) farm planning research and its practical application, and (e) agricultural policy implications of technological innovations in agriculture.
The seminar sessions were an outgrowth of a symposium sponsored previously by TVA in June, 1955. The earlier symposium dealt mainly with methodological procedures in the economic analysis of fertilizer use data. It resulted from several meetings on the economics of fertilizer use. The initial conference conducted by TVA in June, 1953, developed from a suggestion made by Dr. Joseph Ackerman, Managing Director of the Farm Foundation. Since that time Dr. Ackerman has aided the development of research in the economic interpretation of fertilizer response data through the sponsorship of regional farm management research projects sponsored by the Farm Foundation.
The 1956 seminar sessions were designed to integrate the thinking of agronomists, economists, and statisticians on agricultural problems, but on a much broader basis than for previous conferences. The papers presented at the 1956 seminar sessions form the basis of this book. The objectives of the seminars and the book are to examine the most recent thought and research findings on the many aspects of fertilizers in the American economy; and to present new methodological techniques that will enable the more efficient handling of difficult research problems related to fertilizers, and at the same time secure more meaningful answers for practical application.
TVA is concerned with agronomic and chemical development problems which have a direct bearing upon the economic evaluation of
Preface
PREFACE
fertilizers (Parts II and III). Statisticians discuss some modifications of existing statistical methodologies, as well as new ideas about handling such difficult methodological problems as the economic analysis of fertilizer use in crop rotations (Part III). Included in this book are some chapters on timely problems related to fertilizer marketing (Part 11). There are many problems involved in determining the most efficient marketing system for fertilizer. Some of the problems that might lead to greater efficiency in the marketing of fertilizer are considered.
"Programming a Fertilizer Mixing Operation" is the only chapter contained in this book that was not formally presented at the seminar. Due to other commitments, Earl R. Swanson was not able to attend the meetings.
A debt of gratitude is owed particularly to those in the Tennessee Valley Authority's management who made possible this seminar and its reporting in this book, and to the Iowa State College Press, through which publication was effected. Appreciation is extended to Lois R. Carr, Agricultural Economics Branch, Division of Agricultural Relations, Tennessee Valley Authority, for her fine cooperation in preparing the manuscript for publication.
The editors believe that the information presented in this book will contribute materially to the improvement and expansion of economic research in the interpretation of agronomic data, fertilizer production and distribution, and the use of fertilizer in whole-farm planning.
E. L. BAUM
Tennessee Valley Authority
Knoxville, Tennessee
EARL 0. HEADY
Iowa State College
Ames, Iowa
JOHN T. PESEK
Iowa State College
Ames, Iowa
CLIFFORD G. HILDRETH
Michigan State University
East Lansing, Michigan
October, 1956
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 1
Leland G. Allbaugh, Tennessee Valley Authority
PART 1: PHYSICAL AND ECONOMIC ASPECTS OF WATER
SOLUBILITY IN FERTILIZERS
2. General Considerations Regarding Water Solubility of
Fertilizers and Availability to Crops . . . . . . . . . . 7
George Stanford, Tennessee Valley Authority
3. Economic Interpretation of the Importance of Water
Solubility in Phosphorus Fertilizers When Used as
Hill Fertilizer for Corn . . . . . . . . . . . . . . . . . 15
John T. Pesek and John R. Webb, Iowa State College
4. Technical and Economic Factors Involved in Production
of Fertilizers of High Water-Soluble P20r, Content by
Conventional Processes . . . . . . . . . . . . . . . . . 29
T. P. Hignett, Tennessee Valley Authority
5. Crop Response to Commercial Fertilizers in Relation to
Granulation and Water Solubility of the Phosphorus 37
G. L. Terman, Tennessee Valley Authority
PART H: AN EXAMINATION OF LIQUID FERTILIZERS
AND RELATED MARKETING PROBLEMS
6. Factors Affecting the Evaluation of Liquid Fertilizers 57
L. S. Robertson, J. F. Davis, and C. M. Hansen
Michigan Agricultural Experiment Station
7. Economics of Manufacture of Liquid Mixed Fertilizers . 61
Z. A. Stanfield, Tennessee Valley Authority
CONTENTS
8. Programming a Fertilizer Mixing Operation . . . . . . . 72
Earl R. Swanson, University of Illinois
9. The Potential Market for Liquid Fertilizer . . . . . . . 77
Harold G. Walkup and John N. Mahan
Tennessee Valley Authority
10. Economic Comparison of Farm Application of Dry
and Liquid Types of Nitrogen in Iowa . . . . . . . . . . 89
Earl 0. Heady, Iowa State College
E. L. Baum, Tennessee Valley Authority
11. Methods of Studying Attitudes Relevant to the Economics
of Fertilizer Marketing . . . . . . . . . . . . . . . . . 115
Norman Nybroten, West Virginia University
PART III: METHODOLOGICAL PROCEDURES IN THE STUDY
OF AGRONOMIC AND ECONOMIC EFFICIENCY IN RATE OF APPLICATION, NUTRIENT RATIOS, AND
FARM USE OF FERTILIZER
12. Over-All Economic Considerations in Fertilizer Use 125
E. L. Baum, Tennessee Valley Authority
Earl 0. Heady, Iowa State College
13. An Agronomic Procedure Involving the Use of a Central
Composite Design for Determining Fertilizer Response
Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . 135
Bruce L. Baird and J. W. Fitts,
North Carolina State College
14. Some Methodological Considerations in the Iowa-TVA
Research Project on Economics of Fertilizer Use . . . 144
Earl 0. Heady and John T. Pesek
Iowa State College
15. A Suggested Procedure for Agronomic-Economic
Fertilizer Experiments . . . . . . . . . . 168
Thomas E. Travel, Mississippi State Coiieg*e*
16. Possible Models for Agronomic -Economic Research 176
Clifford Hildreth, Michigan State University
17. Some Statistical Problems in the Analysis of Fertilizer
Response Data . . . . . . . . . . . . . . . 187
R. L. Anderson, North Carolina State Colie;e* ' * * '
CONTENTS
18. Some Statistical Aspects of the TVA-North Carolina
Cooperative Project on Determination of Yield
Response Surfaces for Corn . . . . . . . . . . . . . . . 207
David C. Hurst and David D. Mason
North Carolina State College
19. Planning Agronomic-Economic Research in View
of Results to Date . . . . . . . . . . . . . . . . . . . . 217
Glenn L. Johnson, Michigan State University
20. Problems Involved in the Integration of Agronomic and
Economic Methodologies in Economic Optima
Experiments . . . . . . . . . . . . . . . . . . . . . . . 226
L. S. Robertson, G. L. Johnson, and J. F. Davis
Michigan Agricultural Experiment Station
PART IV: FARM PLANNING PROCEDURES
FOR OPTIMUM RESOURCE USE
21. Some Problems and Possibilities of Farm
Programming . . . . . . . . . . . . . . . . . . . . . . 243
Clifford Hildreth, Michigan State University
22. The Role of Management in Planning Farms
for Optimum Fertilizer Use. . . . 261
Glenn L. Johnson, Michigan State university*
23. Methodological Problems in Programming Farms . . . . 271
Earl 0. Heady, Iowa State College
E. L. Baum, Tennessee Valley Authority
24. Programming Part-Time Farms in Georgia . . . . . . . 283
Fred B. Saunders, University of Georgia
25. An Application of Linear Programming Techniques to the
Planning of Commercial Farms in North Georgia . . . 299
Roger Woodworth, University of Georgia
26. Relations of Farm Resource Use to Farm Family Incomes
and Hydrology in the Parker Branch Watershed . . . . 316
A. J. Coutu and C. E. Bishop North Carolina State College
CONTENTS
PART V: AGRICULTURAL POLICY IMPLICATIONS
OF TECHNOLOGICAL CHANGE
27. Reflections on Agricultural Production,
Output, and Supply .
Theodore W. Schultz, University of Chicago
. . . 335
28. Need for Production Economics Research
in Solving Policy Problems . . . . . . . . . . . . . . . 348
Earl 0. Heady, Iowa State College
29. Some Contributions of Microanalysis
to Agricultural Policy . . . . . . . . . . . . . . . . . . 362
Glenn L. Johnson, Michigan State University
30. The Economist and National Policy in Relation to
Low-Income Farm Families . . . . . . . . . . . . . . 375
Charles E. Bishop, North Carolina State College
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387
List of Figures
Figure
Number Title
4.1.--Effect of degree of ammoniation on water solubility
of P205 in ordinary superphosphate . 30
4.2.--Effect of degree of ammoniation on water solubility
of P20 in concentrated superphosphate . 31
5.1.--Effect of granule size and percent water-soluble P on mean
relative yields of two greenhouse crops of Sudan-grass and
oats. (Mean yield of each crop from all phosphate
fertilizers on 2 Tennessee and 3 Virginia soils = 100.) . . 46
5.2.--Effect of granule size and percent water-soluble P on mean
relative yields of wheat forage in Mississippi. (Mean yield
from all phosphate fertilizers in 4 field experiments
= 100.) . . 47
5.3.--Effect of granule size and percent water-soluble P on mean
relative yields of corn grain and seed cotton in Georgia,
Kentucky, and Tennessee. (Mean yield from all phosphate
fertilizers in 6 corn and 1 cotton experiments = 100.). . . 49
5.4.--Effect of granule size and percent water-soluble P on mean
relative yields of vegetable crops in Washington. (Mean
yield from all phosphate fertilizers in 5 experiments
= 100.) . . 50
7.1.--Effect of sales volume and seasonal operation on selling
price in South Atlantic region . . 64
7.2.--Effect of sales volume and seasonal operation on selling
price in Pacific region . 65
10.1.--Fixed costs per acre for selected sizes and combinations of equipment in applying high-pressure nitrogen
fertilizer . . 102
xiv LIST OF FIGURES
10.2.--Fixed costs per acre for selected sizes and combinations of equipment in applying dry-type and non- and low-pressure
nitrogen fertilizer . . 103
10.3.--Comparison of total costs (fixed plus variable) with labor included as cost for dry-type and high-pressure nitrogen
fertilizer--50 pounds of N per acre . 104
10.4.--Comparison of total costs (fixed plus variable) with labor included as cost for dry-type and non- and low-pressure
nitrogen fertilizer--50 pounds of N per acre . 105
10.5.--Comparison of total costs (fixed plus variable) with labor included as cost for dry-type and high-pressure nitrogen
fertilizer--100 pounds of N per acre . 106
10.6.--Comparison of total costs (fixed plus variable) with labor included as cost for dry-type and non- and low-pressure
nitrogen fertilizer--100 pounds of N per acre . 107
10.7.--Less costly machines: fixed costs per acre for selected sizes and combinations of equipment in applying dry-type
and high-pressure nitrogen fertilizer . 108
10.8.--Less costly machines: fixed costs per acre for selected sizes and combinations of equipment in applying dry-type
and non- and low-pressure nitrogen fertilizer . .109
14.1.--Predicted yield surface for corn on Carrington soil. . . . 149
14.2.--Ninety-five percent confidence limits for corn response to K20 at 104 pounds of N (dashed vertical line is limit
of K20 in experiment) . 150
14.3.--Isoquants and isoclines. Dashed lines are ridge lines ON OK
denoting - and - values of zero. Ratios attached
OK 9N
to isoclines are price ratios denoting expansion paths.
Yield figures are attached to isoquants . 151
14.4.--Production surface for corn on Moody soil predicted from equation 14.9 . . 153
14.5.--Yield isoquants and isoclines for Moody soils. Dotted OP ON
lines are !-- and ! zero, the ridge lines of the
predicted surface . . . 154
LIST OF FIGURES xv
14.6. --Predicted P-K yield surface with no N application.157 14.7. --Predicted P-K yield surface at 40 pounds of N . . .158 14.8. --Predicted P-K yield surface at 80 pounds of N . . .159 14.9.--Yield isoquants and isoclines with dashed ridge lines at zero level K20. Equalities on isoclines indicate price
for N as a ratio of the price for K,20. Derived from
equation 14.12 . . . . . . . .160 14.10.--Yield isoquants and isoclines with dashed ridge lines at
zero level of N. Derived from equation 14.14. . . .161 14.11. --Nonlinear isoclines for a soil completely deficient in
two nutrients . . . . . . . .162 14.12. --Alternative nonlinear isoclines for soil conV~petely
deficient in two nutrients. . . . . . .163 14.13.--Linear isoclines with available quantities of both
nutrients originally in the soil. . . . . .165 16. 1. --Distribution of observations. . . . . .184 1'7.1.--Increasing-decreasing returns response curve . . .192 18. 1. --Graphical representation of treatment combinations of the composite design (table 18.1 for actual rates corresponding
to code). . . . . . . . .210 23.1. --Alternative outcomes under budgeting and linear programming . . . . . . . .276 24.1. --Conceptual definition of part-time farming. . . . .284 24.2. --Illustration of enterprise relationships between farm and nonfarm activities. . . . . . .286 24.3. --Illustration of the application of choice criteria for assumed relationship between farm and nonfarm
activities. . . . . . . . .288
List of Tables
Table
Number Title
3.1. Sources and Water Solubilities of Phosphates Used in the
Hill Fertilization Experiments From 1952 to 1955. . 17
3.2. Equations Expressing the Estimated Yield, Y, as a
Function of Rate Of P205 in the Hill, P, and the
Percent Water Solubility, S . . . . . . . . . . . . . . . . . 18
3.3. Multiple Correlation Coefficients and t - Values for
Regression Equations Presented in Tible 3.2 . . . . . . . 19
3.4. The Maximum Predicted Yield Increases in Bushels Per
Acre and Rate Of P205 at Maximum As Computed From
Equation 3.1 for 1953, 1954, and 1955, and the Maximum
Predicted Yield by the Spillman Equation 3.7 . . . . . . . 21
3.5. Optimum Rates Of P205 and Estimated Increases in Yield
of Corn for Specified Price Ratios of P205 to Corn (Pp/Pc)
for Phosphorus Materials of Different Water Solubility. . 23
3.6. The Optimum Rates of P205 at Selected Pp/Pc Ratios
and the Expected Increases in Yield at Certain Levels
of Water Solubility of the Phosphorus. Calculations
Are Based on Equations 1953, 3.2;. 1954, 3.2; and
1955, 3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.7. Percent of Water-Soluble P20, at Which Maximum
Yields Are Reached in 1953, 1954, and 1955 as Estimated
by Two Forms of the Regressions Used . . . . . . . . . . 25
4.1. Formulations and Costs for 3-12-12 . . . . . . . . . . . . 32
4.2. Formulations and Costs for 5-20-20 . . . . . . . . . . . . 33
4.3. Formulations and Costs for 10-10-10 . . . . . . . . . . . 34
4.4. Formulations and Costs for 12-12-12 . . . . . . . . . . . 35
5.1 Crop Response to TVA Diammonium Phosphate
Fertilizers, 1950-55 . . . . . . . . . . . . . . . . . . . . 43
xvi
LIST OF TABLES xvii
5.2. Fertilizers Used in the Granule Size and Water
Solubility Experiments . . . . . . . . . . . . . . . . . . . 44
6.1. The Effect of Liquid and Solid Fertilizers on
Corn Yields in 1955 . . . . . . . . . . . . . . . . . . . . . 59
6.2. The Effect of Liquid and Solid Fertilizers on Yields
of Onions, Table Beets, and Carrots Grown on
Houghton Muck in 1955 . . . . . . . . . . . . . . . . . . . 60
7.1. Effect of Plant Size on Operating Costs in Liquid
and Solid Mixed Fertilizer Plants . . . . . . . . . . . . . 65
7.2. Formulation Costsfor Several Grades of Liquid
and Solid Mixed Fertilizer . . . . . . . . . . . . . . . . . 66
7.3. Effect of Increasing Concentration of Solids . . . . . . . . 67
7.4. Estimates of Selling Price of 10-10-10 Liquid and Solid
Fertilizer (Sales Volume: 40,000 Tons Per Year; Plants
Operated 6 Months Per Year To Produce 40,000 Tons) 68
7.5. Estimated Costs of Distribution of Solid and Liquid
Fertilizers (Sales Volume: 5,000 Tons; Cost Delivered
to Farm) . . . . . . . . . . . . . . . . . . . . . . . . . . 69
7.6. Estimated "Delivered to Farm" Selling Prices for
40,000-Ton Annual Sales Volume (One Manufacturer
and Eight Distributors) . . . . . . . . . . . . . . . . . . . 70
8.1. Composition of Fertilizer Material . . . . . . . . . . . . . 73
8.2. Price Situations Used To Compute Materials Needed To Minimize Cost of a Ton of Neutral 4-12-4 . . . . . . . 73
8.3. Quantities of Materials Needed To Minimize Cost
of a Ton of Neutral 4-12-4 . . . . . . . . . . . . . . . . . 74
9.1. Plant Nutrient Consumption Per Acre of Crops and
Pasture Land . . . . . . . . . . . . . . . . . . . . . . . . 79
9.2. Consumption of Liquid Fertilizers in the United States
and Territories (Short Tons of Material as Applied) . . . 82
9.3. Consumption of Liquid Fertilizers in California . . . . . . 83
10.1. Fixed Costs for Different Methods of Nitrogen Application
and Different Sizes of Equipment. Costs Figured on a
Basis of 1955 Prices . . . . . . . . . . . . . . . . . . . . 92
xviii
LIST OF TABLES
10.2. Total Investment in Equipment and Storage Tanks for
Selected Dry- and Liquid-Form Distribution Systems . . . 93
10.3. Total Fixed Cost Per Acre for Alternative Methods
of Fertilizer Application . . . . . . . . . . . . . . . . . . 94
10.4. Total Cost Per Acre of Applying Fertilizer (Fixed Plus
Variable With Cost of Nutrients Excluded) for Alternative
Methods of Fertilizer Application (Labor Included in
Costs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
10.5. Total C ost Per Acre of Applying 50 Pounds of Nitrogen
Per Acre for Alternative Methods of Fertilization
Application (Labor Included as a Cost) . . . . . . . . . . . 96
11.1. Farmers' Opinions on Bases for Discounts on Fertilizer
Prices Other Than Paying Cash . . . . . . . . . . . . . . 118
11.2. Farmers' Valuations of Delivery Service for Fertilizer
and Whether Fertilizer Was Hauled by the Dealer or the
Farmer for Three Relationships of the Valuations and
the Dealer's Charge or Discount for Hauling . . . . . . . 120
13.1. Fertilizer Treatments of Fertility Trials With Corn
in North Carolina in 1955 . . . . . . . . . . . . . . . . . . 137
13.2. The Average Yield of Shelled Corn at 15.5 Percent
Moisture for Selected Locations of Fertility Trials
in 1955 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
13.3. The Average Results of Chemical Analysis of Soil
Samples Collected From the Surface Soil in 1955 . . . . . 140
13.4. Rainfall for the Months of June and July at Locations
of Selected Trials in 1955 . . . . . . . . . . . . . . . . . 141
14.1. Analysis of Variance of Corn Yields on Carrington
Soil, Randomized Block Design . . . . . . . . . . . . . . . 146
14.2. Values of t for Coefficients of Individual Block
Regressions and Test of Difference Between
Corresponding Coefficients of the Two Blocks . . . . . . . 147
14.3. Analysis of Variance for Regression of Corn Yield . . . . 148
14.4. Analysis of Variance of Corn Yields on Moody Soil,
Randomized Block Design . . . . . . . . . . . . . . . . . 152
LIST OF TABLES xix
14.5. Analysis of Variance of Corn Yields on Haynie Soil,
Randomized Block Design . . . . . . . . . . . . . . . . 155
14.6. Values of t for Individual Regression Coefficients
of Equation 14.10 . . . . . . . . . . . . . . . . . . . . . . 156
15.1. Design Matrix, Squares, and Cross Products for Box's
Second-Order Composite Design With Treatment Combinations on Each Major Aids Taken To Be Two Increments
of Each Variable . . . . . . . . . . . . . . . . . . . . . . 171
15.2. Design Matrix, Squares, and Cross Products for Modified
("Triple Cube") Second-Order Design of Same "Size" as
Box's Design in Table 15.1 . . . . . . . . . . . . . . . . . 172
15.3. Form of Matrix of Sums of Squares and Cross Products
for Box's Second-Order Composite Design and "Triple
Cube" Design . . . . . . . . . . . . . . . . . . . . . . . 173
15.4. Elements of Matrices of Sums of Squares and Sums
of Cross Products for Both Original Box Design and
"Triple Cube" Design . . . . . . . . . . . . . . . . . . . . 173
15.5. Form of Inverse Matrix for Both Original Box Design
and "Triple Cube" Design . . . . . . . . . . . . . . . . . 173
15.6. Elements of Inverse Matrix for Both Original Box
Design and "Triple Cube" Design . . . . . . . . . . . . . 173
15.7. Correlation Between Coefficients for Both Original
Box Design and "Triple Cube" Design . . . . . . . . . . . 174
15.8. NC ii of Original Box Design and of "Triple Cube"
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
17.1. Equations for Iowa Data . . . . . . . . . . . . . . . . . . 188
17.2. Mean Estimated Corn Yields (Bu. Per Acre) as Derived
by Use of Various Production Functions for Iowa Data . . 189
17.3. Estimated Optimal Nitrogen Applications (in Pounds) for
Various Input-Output Price Ratios As Derived by Various
Production Functions for Iowa Data . . . . . . . . . . . 191
17.4. Observed and Estimated Yields, 25V1, and 95 Percent
Confidence Limits for Each of Eight Points . . . . . . . . 203
17.5. Estimated Optimal Yields for Five Values of r and
for Each Estimating Equation . . . . . . . . . . . . . . . 205
xx LIST OF TABLES
18.1. Rates in Pounds Per Acre and Coded Levels of N, P205, and K20 Used in Forming Treatment Combinations
for the Composite Design (Figure 18.1) . . . . . . . . . . 210
18.2. Parameter Estimates and Their Variances as Estimated on 6 Norfolk-Like Soils . . . . . . . . . . . . . . . . . . . 213
23.1. Use of Negative Coefficients in Simplex Calculations . . . 280
24.1. Description of Part-Time Farming Situations Included in Analysis Under Approach 1 (Determining Farm
Situation To Combine With a Given Nonfarm Job) . . . . . 293
24.2. Comparison of Returns for All Part-Time Farming Situations With the Basic Farm Situations . . . . . . . . . 295
24.3. Comparison of Farm Organization for All Part-Time Farming Situations With the Basic Farm Situations
(Only for Situations Under Approach 1) . . . . . . . . . . 297
25.1. Resource Requirements and Income for 26 Alternative Activities Used in Programming . . . . . . . . . . . . . . 302
25.2. Farm Plan 1, Maximum Income Farm Plan for Situation A (Investment Plus Operating Capital Limited to
$3000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
25.3. Marginal Value Productivities of Resources for Highest Income Farm Organization for Situation A
(Operating and Investment Capital Limited to $3000) . . . 310
25.4. Opportunity Costs, Net Income Per Unit and Marginal Revenues for Highest Income Plan, Situation A . . . . . . 311
25.5. Comparison of Maximum Farm Organizations for Four Situations- -Case -Study Farm . . . . . . . . . . . . . . . 313
25.6. Comparison of Marginal Value Productivities for Resources for Four Situations, Case-Study Farm . 314
27.1. Recent Changes in Output and Input in Agriculture in the United States . . . . . . . . . . . . . . . . . . . . . 339
27.2. Recent Changes in Output and Input in Agriculture in Brazil, Mexico, and Argentina . . . . . . . . . . . . . . 341
27.3. Recent Changes in Output and Input in Agriculture in the U.S.S.R . . . . . . . . . . . * . . . . . . . . . . . . . 343
LELAND G. ALLBAUGH
Tennessee Valley Authority
Chapter I
Introduction
NTEREST in economic problems of fertilizer use has been stimulated among economists, agronomists, and statisticians during the
past several years. In exploring methodological research problems, Fiviessional. workers from these three fields have developed a mutual respect for each other's abilities and viewpoints. At the same time, they have become more keenly aware of the possible contributions each could make to the solution of common problems.
Agricultural economists depend upon research in the many production sciences for basic data. Accordingly, they perhaps recognize the need for the integration of scientific skills more than other groups of professional workers. However, agricultural production scientists also are beginning to recognize the need for a better understanding of the economic problems which their research is expected to solve. Hence, a coordinated approach to research on fertilizers and basic resource development is becoming widely accepted.
Interest in the economics of fertilizer use subsided after the important contributions made by Mitscherlich, Liebig, and Spillman. It is difficult to explain why so little research was conducted in the economics of fertilizer use from 1925 to 1953. Since 1953, this field of research has expanded rapidly. The Farm Foundation, through its sponsorship of regional farm management research committees, along with economists and agronomists in the land-grant colleges, the USDA, and TVA have had a part in this resurgence of research interest in agronomic and economic efficiency in the rate of application, nutrient ratios, and farm use of fertilizers.
Section 5 of the TVA Act is the basis for TVA's interest and responsibility in the economic development and economic use of new and improved fertilizers. Because of this national responsibility, TVA recognizes the need for helping in the rapid development of improved research methodologies, both agronomic and economic, and the use of such information in educational programs. TVA's national fertilizer and munitions laboratory at Wilson Dam, Alabama, is mainly concerned with developing new and improved techniques of manufacturing chemicals for fertilizers and defense purposes. The development of new and improved fertilizers which lower the cost of plant nutrients to the American farmer enables food and fiber to be produced more efficiently.
L. G. ALLBAUGH
Section 22 of the Act also delegates to TVA the regional responsibility for the efficient development of resources in the Tennessee Valley. As a resource development agency, TVA is vitally concerned with the economic well-being of the people living in the Valley. In the public interest, TVA conducts studies and related educational activities designed to increase efficiency in the farming and rural life of the Valley area. In addition, it Is a TVA policy to conduct most of its agricultural research activities through the land-grant colleges.
TVA considers the role of fertilizer to be important in its resource development programs. TVA emphasizes the use of fertilizers for proper land cover in its tributary watershed programs, and in planning farming systems for maximum profits. In the Tennessee Valley states, fertilizers and water are as essential as sunshine and soil to agricultural production.
Upon the suggestion of Dr. Joseph Ackerman, Managing Director of the Farm Foundation, TVA arranged a conference in June, 1953, with interested professional workers to discuss the possibilities of undertaking research in the economics of fertilizer use. Representatives of the Southern Farm Management Research Committee, the USDA, the Farm Foundation, and the TVA staff and its consultants attended this meeting in Knoxville. No agronomists were present at this initial meeting.
A follow-up meeting was held at Muscle Shoals in January, 1954. In addition to the group attending the 1953 meeting, several agronomists and statisticians participated in the discussions, and a new field of research emphasis was initiated. Consideration was given to needed methodological procedures for handling developments in fertilizer economics. From these meetings, it became evident that research in fertilizer economics should be broader in scope. Fertilizer response research should consider not only the three major applied plant nutrients; it should include also such other considerations as soil type, fertilizer placement, and the time and method of application. Experiments including these variables ought to be conducted for multicrop rotations, .as well as for single crops.
The increased amount of research in the economics of fertilizer use has been helped greatly by the interest of the various regional farm management research committees sponsored by the Farm Foundation; the continuing interest of the USDA; the interest of agronomists, economists, and statisticians at the land-grant colleges; and the increased interest of the nation's fertilizer industry.
A third meeting, sponsored by TVA, was the June, 1955, symposium held at Knoxville. The papers presented at the symposium pointe , d up areas for new work in agronomic- economic research.' Methodologies used in the past were examined; alternative methodologies were
'The symposium on Methodological Procedures in the Economic Analysis of Fertilizer Use Data was held in Knoxville, June 14-16, 1955. These papers were published in Methodological Procedures in the Economic Analysis of Fertilizer Use Data, Iowa State Co7-ege Press, 1956.
INTRODUCTION
proposed to handle better the problems involved. Following these several meetings, sufficient research progress had been made to warrant a conference sponsored by TVA in March, 1956. This volume includes the papers presented at the latter conference.
The purpose of this book is to present information on research conducted in the land-grant college-TVA cooperative agricultural economic research program, to describe new methodological techniques enabling more efficient analysis of difficult research problems, to indicate problems in need of solution, and to provide meaningful answers to practical farm problems.
Exchange of ideas among agronomists, economists, and statisticians on research methodologies and agricultural policy problems not only leads to better mutual understanding but also provides a basis for more effective research. This need was stressed by a quote appearing in the USDA Agricultural Research Service letter of March 9, 1956, by Dr. Harry C. Trelogan, Director of the AMS Marketing Research Division. He stated: "One of the greatest needs of our present-day agricultural research system is.a common language, better understanding, and closer working relationships among the various specialized subject-matter fields."
One purpose of this book is to fulfil this need. Another is to stimulate more meaningful research, with the objective of bettering the economic and social welfare of agriculture and the nation. Some chapters are concerned with means of obtaining a better application of research results. Discussion between extension and research personnel, in carrying out the TVA program, suggests that some important fundamental research is lacking. These gaps sometimes occur because the research worker does not look far enough ahead to determine how the proposed results of his research might best be conveyed to the extension worker, and how the results might be applied in practical situations on farms and in agricultural industries.
Fundamental research ordinarily is several steps away from the extension application. However, if research is useful, its results must be disseminated at some future time. Accordingly, the research worker should give some thought to the possible use of his results in determining the framework for analyzing his problem. This problem of coordination is similar to the problem of establishing better understanding between the production scientist and the agricultural economist, who often can make their research more meaningful with full cooperation. TVA is interested in bringing about a closer coordination of research and extension - in the selection of research problems and the use of research information in extension programs. This volume not only emphasizes methodological needs and basic research results for a more fundamental solution of fertilizer economic problems; it also stresses the need for integration of research results and extension application in solution of farm problems.
PART I
Physical and Economic Aspects of Water Solubility in Fertilizers
0, Solubility and Availability to Crops
0- Economics of Water Solubility
0- Relative Crop Response
i
GEORGE STANFORD
Tennessee Valley Authority
Chapter 2
General Considerations Regarding
Water Solubility o/ Fertilizers
and Availability to Crops
OIL scientists have recognized that poor correlation exists between
the content of water-soluble soil nutrients and the capacity of soils to supply nutrients to plants. Concentrations of various major essential nutrients present in the soil solution, even in fertile soils, are very low at any particular instant and would not supply plant requirements for any appreciable time. The nutrient- supplying capacity of a soil, therefore, is dependent on rate of replenishment by dissolution of the soil minerals and by ion exchange from colloidal surfaces, as well as on concentration of nutrients in the soil solution. Water solubility of nutrients in fertilizers applied to soils likewise bears no simple relation to plant availability. The instant that a dissolved salt contacts the soil, it essentially loses its identity through reaction with soil constituents.
Consideration will be given in this chapter to the water-soluble
compounds of nitrogen, phosphorus, and potassium contained in fertilizers and their behavior when applied to soils. Particular emphasis will be placed on plant availability of applied nutrients in relation to soil-fertilizer reactions.
NITROGEN
Nitrogen Fertilizers (9,11)1
The principal nitrogen fertilizers are liquid anhydrous ammonia (82 percent N), ammonium nitrate (33.5 percent N), ammonium sulfate (20 percent N), ammonium phosphates (11-21 percent N), and urea (46 percent N). Other less extensively used materials are sodium nitrate (16 percent N) and calcium cyanamide (20-21 percent N). All of these carriers are water soluble. Those designated above as principal carriers are used for soil application both in solid form and in solution, except for anhydrous ammonia which occurs as liquid under pressure. Nitrogen solutions being used for direct application are anhydrous ammonia,
'Numbers in parentheses which appear in sentences refer to reference citations listed at the end of each chapter.
GEORGE STANFORD
aqua ammonia, urea, urea-ammonium nitrate, solutions of ammoniaammonium nitrate, ammonia-urea, or ammonia-ammonium nitrateurea. The solutions containing ammonia plus nitrogen salts, however, are primarily used in production of mixed solid fertilizers (see Chapter 4).
The water-insoluble nitrogen fertilizers, principally natural organic proteinaceous materials, comprise less than 5 percent of the nitrogen sold in fertilizers. Recently, synthetic urea-formaldehyde, a slowly soluble nitrogen source, has come into limited commercial production
(9).
Behavior of Nitrogen Fertilizers in Soils
Ammonia (NH3), ammonium ion (NHC), nitrate ion (NO), and urea [(NH2)2 CO] are the chemical forms comprising practically all the nitrogen marketed in fertilizers. When ammonia is injected in soil, it is converted to the ammonium form either through reaction with carbonic acid of the soil solution (equation 2.1), or direct attachment to negatively charged soil colloids through neutralization of hydrogen (H+) ion (equation 2.2).
(2.1) 2NH + H2CO3 - (NH4)2CO3
(2.2) NH3 + Hn-colloid -- Hn_,NH4-colloid
Ammonium salts such as (NH4)20O4 when dissolved in the soil water ionize rather completely to give NH4+ and S04= ions. Some of the NH4+ ions become adsorbed through replacement of cations already held on soil colloid surfaces (equation 2.3), while some remain in the soil solution.
(2.3) 3NH+ + HCa-colloid-- (NH4)3-colloid + H+ + Ca++
Urea hydrolyzes to form (NH4)2CO3 as in equation 2.4. The ammonium ions thus produced, as well as those represented in equation
2.1, may react with soil colloids as depicted in equation 2.3.
(2.4) (NH2)2CO + 2 HOH -- (NH4)2CO3
The negatively charged nitrate ion does not react with soil colloids of like charge nor does it enter directly into formation of insoluble inorganic compounds in soils. Thus, extraction with water readily removes nitrates from soils.
Fixation of ammonium ions by particular types of clay minerals is known to occur in certain soils. Further study is needed, however, to determine the significance of NH4-mineral formation in relation to efficiency of nitrogen fertilizer use (2, 3, 6, 7).
WATER SOLUBILITY OF FERTILIZERS
Biological Transformations of Nitrogen
Both ammonium and nitrate forms of nitrogen are utilized by soil microorganisms during active decomposition of crop residues. The accompanying disappearance of soluble inorganic nitrogen forms, termed immobilization, often results in temporary deficiencies of nitrogen to growing crops in soils possessing low reserves of easily mineralizable nitrogen (16).
As readily available energy sources such as crop residues become depleted, ammonium nitrogen is again released by decomposition of high-nitrogen microbial tissue. Ammonium ions resulting from organic matter decomposition and those introduced directly through fertilizer application are converted to nitrate ions through the action of nitrifying organisms. Under favorable environmental conditions, this conversion occurs readily (16). In well aerated, fertile soils, and with favorable temperature and moisture conditions prevailing, only 2 to 3 weeks may be required to bring about nearly complete nitrification of ammonium applied in fertilizer.
Availability of Fertilizer Nitrogen to Plants
Plant roots absorb ammonium and nitrate ions. Whether or not there is preferential absorption of either of these forms is a question which must be examined in relation to kind of plant, stage of growth, characteristics of the root environment such as pH, oxygen supply, concentration of other ions capable of influencing ammonium or nitrate uptake, and other factors (10). It is sufficient to point out that certain crops (potatoes, corn, rice, and buckwheat, for example) prefer ammonium nitrogen while others (beets and wheat) thrive better on nitrate nitrogen (10). Numerous plants feed equally well on both forms. Normally, however, nitrate is the dominant form presented to the roots during much of the growing season, regardless of the form applied. It is not surprising, therefore, that comparisons of nitrogen sources in field experiments frequently reveal no differences in crop response.
Mobility of Fertilizer Nitrogen in Soils
As would be anticipated from equation 2.2, adsorbed ammonium ions are relatively immobile in soils. That is, percolating waters move little of this form of nitrogen below the application zone in medium to heavy-textured soils. Under Midwestern conditions, late fall application of ammonia or ammonium salts is deemed an acceptable practice, since prevailing low temperatures reduce the rate of nitrification, and losses of nitrogen over winter and early spring likely are of minor consequence (17).
Nitrate nitrogen, on the other hand, is readily leached, especially in
GEORGE STANFORD
coarse-textured soils. Moreover, nitrate ions move upward in the capillary stream of water as the soil surface dries. During prolonged dry periods, a high concentration of nitrate may accumulate in a few inches of surface soil and become effectively unavailable to growing plants (13). A redistribution takes place, of course, with further rainfall. Thus, in relatively dry seasons, deep placement may prove superior to shallow broadcast application of nitrogen, since the plant roots utilize more nitrogen from the deeper moist zone than from the extremely dry surface layer.
The ready mobility of nitrate nitrogen accounts for the high recovery (60 percent or more) of applied nitrogen by plants (8). Such a high recovery is evidence of the rapidity with which nitrate diffuses from one point to another in the soil solution and to plant root surfaces.
POTASSIUM
Potassium Fertilizers
The principal potassium fertilizer, potassium chloride (50-60 percent KO), accounts for about 90 percent of the consumption of potash fertilizer in the United States (19). Sulfates of potassium account for most of the remainder. Both the chloride and sulfates are water soluble. Another potassium fertilizer of potential importance is potassium metaphosphate, KP031 containing approximately 34 percent K20 which has been produced experimentally by the Division of Chemical Development, Tennessee Valley Authority.
Reactions of Potassium Salts in Soil
Potassium ions react with colloidal surfaces in the same manner as depicted for ammonium ions in equation 2.3. Thus, the mobility of this nutrient ion is relatively restricted once adsorption occurs. That is, mass movement of soil water brings about little leaching where sufficient clay and organic matter are present. Other cations, however, may readily replace the adsorbed potassium.
Some of the potassium ions penetrate between lattice sheets of
certain clay minerals and resist replacement by other cations (20). It is generally believed that the dissolved, adsorbed, and difficultly replaceable potassium tends to equilibrate in soils according to equation
2.5(4, 20).
Adsorbed.*- Fixed
(2.5) K+ in solution ol K K
WATER SOLUBILITY OF FERTILIZERS
Availability of Potassium to Plants
Plant roots readily absorb potassium ions (K+) from solution.
From equation 2.5, it is evident that there will be a tendency toward replenishment of soil solution potassium as plant absorption lowers the concentration in solution or is adsorbed. Soils differ, however, in the rate at which this readily available form of potassium is replenished. There is evidence that plant roots, in intimate contact with colloidal clay and organic matter, obtain potassium ions by "contact exchange"
(12). This is illustrated in equation 2.6, in which a hydrogen ion adsorbed on the root surface is pictured as exchanging with a potassium ion on the colloid surface.
(2.6) H-Root + K-colloid 0 K-Root + H-colloid
Except in soils which fix appreciable amounts of potassium in slowly replaceable form or those which possess little clay and organic matter and, therefore, permit extensive leaching losses, recovery of applied soluble potassium fertilizer is relatively high - often 50 percent or greater (16).
Slowly Soluble Potassium Fertilizers
With very large application of soluble potassium fertilizer, it frequently has been observed that certain plants absorb larger quantities of potassium than are required for maximum yield (16). Brief consideration has been given to the importance of leaching losses in sandy, low-colloid soils subjected to high rainfall. In some soils, the fixation of potassium (equation 2.5) becomes important enough to affect greatly recovery and efficient use of applied potassium (1, 22). These observations suggest the need for a slowly soluble potassium fertilizer for most efficient use under certain conditions. Such a fertilizer ideally should dissolve slowly enough to prevent "luxury consumption" by plants, reduce the proportion lost by leaching, and minimize fixation where these factors are problems.
Phosphorus- potassium fertilizer containing chiefly a slowly soluble potassium- calcium pyrophosphate and potassium metaphosphate has been prepared on an experimental scale in the Division of Chemical Development, TVA. Products of this nature varying widely in water solubility are currently being compared with completely water-soluble sources such as vitreous potassium metaphosphate, potassium chloride, and potassium sulfate in greenhouse pot tests at Wilson Dam.
GEORGE STANFORD
PHOSPHORUS
Water- Soluble Phosphorus Fertilizers
The chief water-soluble phosphorus carriers are ordinary superphosphate (18-20 percent P205), concentrated superphosphate (45-50 percent P205), f ertilizer- grade monoammonium phosphate (48 percent P205), diammonium phosphate (53 percent P,205), and phosphoric acid (62 percent P20,). The superphosphates, when used in manufacture of mixed fertilizers, usually are ammoniated in the process of formulation. The water- soluble phosphorus present following ammoniation is predominantly ammonium phosphate (see Chapter 5). Liquid fertilizers containing phosphorus are prepared by ammoniating phosphoric acid. Usually, about equal proportions of the monoammonium and diammonium phosphates are present (21).
Upon ammoniation of superphosphates in formulation of mixed fertilizers, the water solubility of phosphorus decreases (see Chapter 4). The relative availability to plants of water-soluble and water-insoluble phosphorus compounds under different soil conditions is discussed in Chapter 5. The scope of this chapter is largely restricted to a consideration of water-soluble fertilizer constituents.
Reactions and Mobility in Soils
When water-soluble phosphorus compounds are applied to soils, reaction with soil constituents occurs rapidly upon dissolution of the fertilizer particles. A variety of compounds might be formed, depending particularly on the pH of the soil. Basic calcium phosphates, particularly dicalcium. phosphate, form readily in neutral to calcareous soils (14, 18). Even in acid soils, appreciable amounts of dicalcium phosphate are formed upon application of soluble phosphates (15). Formation of complex iron and aluminum phosphates likewise occurs to an unknown extent in acid soils (14). This tendency increases as the pH decreases, with its accompanying increase in soluble or active iron and aluminum and decrease in percent saturation of the exchange complex with calcium.
The rapid reactions of applied soluble phosphates with soils make for an extreme lack of mobility. Consequently, in soils there is relatively little movement of phosphorus to plant roots. This contrasts sharply with nitrate, which moves readily. The extent of root development determines the amount of phosphorus uptake by the plant to a much greater extent, therefore, than is the case with nitrate nitrogen. The effective root feeding zone for phosphorus is the thin layer of soil immediately adjacent to active root surfaces (perhaps only a few millimeters in thickness), whereas the entire root-soil zone may be regarded as being involved in supplying nitrogen, and, to a lesser extent, potassium to the plant (8). The limited mobility as well as the slow
WATER SOLUBILITY OF FERTILIZERS
solubility of the compounds formed on reaction between soils and phosphorus fertilizers are responsible for the very low recovery of applied phosphorus (10-20 percent) during the year of application.
Factors Affecting Plant Availability
of Water-Soluble Phosphorus Fertilizers
Effectiveness of water-soluble phosphorus fertilizers applied to soils may be influenced particularly by granule size and method of placement as is discussed elsewhere in this book. For example, on acid soils, larger granules may be more effective than smaller granules; and band placement usually is superior to mixing with the soil. On the other hand, in neutral to calcareous (alkaline) soils, the smaller granules often provide more phosphorus to plants and mixed placement frequently proves superior to banding. Possibly the determining factors are: (a) volume of soil influenced by the fertilizer, and
(b) amount of plant-available phosphorus remaining per unit of soil in the soil-fertilizer reaction zone (5). The relative significance of these factors evidently varies markedly among soils, as indicated above, in comparing acid and calcareous soils. Scattered evidence suggests that the second factor, concentration of available phosphorus per unit of soil, is of particular importance in determining the ability of plants to absorb phosphorus from acid soils. In calcareous soils, the first factor apparently is of relatively greater signify chance.
There is need for more research to determine the specify ic manner in which soluble phosphorus compounds react with soils of varying characteristics. Gradual increase in use of phosphates in solution is another area requiring investigation (21). It is not known whether dissolved phosphates and solid water-soluble phosphates behave similarly under varying soil conditions. Moreover, little evidence is available concerning placement methods and concentrations which result in most effective use of phosphate solutions.
REFERENCES CITED
1. ALLAWAY, H., and PIERRE, W. H., 1939. Availability, fixation and liberation
of potassium in high-lime soils. J. Amer. Soc. Agron. 31:940-53.
2. ALLISON, F. E., KEFAUVER, M., and ROLLER, E. M., 1953. Ammonium
fixation in soils. Soil Sci. Soc. Amer. Proc. 17:107-10.
3. - 1 ROLLER, E. M., and DOETSCH, J. H., 1953. Ammonium fixation and
availability in vermiculite. Soil Sci. 75:173-80.
4. ATTOE, 0. J., and TRUOG, E., 1945. Exchangeable and acid-soluble potassium
as regards availability and reciprocal relationships. Soil Sci. Soc. Amer.
Proc. 10:81-86.
5. BOULDIN, D. R., 1956. Particle size effects of soluble phosphate fertilizers.
Ph.D. Thesis, Iowa State College Library, Ames, Iowa.
GEORGE STANFORD
6. BOWER, C. A., 1950. Fixation of ammonium in difficultly exchangeable form under moist conditions by some soils of semiarid regions. Soil Sci. 70:375-83.
7. -, 1951. Availability of ammonium fixed in difficultly exchangeable form by soils of semiarid regions. Soil Sci. Soc. Amer. Proc. 15:119-22.
8. BRAY, R. H., 1954. A mobility concept of soil-plant relationships. Soil Sci.
78 :9-22.
9. CRITTENDEN, E. D., 1953. Fertilizer Technology and Resources in the United States, Chapter IV. (Edited by K. D. Jacob.) Academic Press, Inc.,
New York.
10. GORING, C. A. I., 1956. The nitrogen nutrition of plants. Down to Earth. 2:7-9.
1.1. GRIBBI'S, M. F., 1953. Fertilizer Technology and Resources in the United
States, Chapter III. (Edited by K. D. Jacob.) Academic Press, Inc., New York. 12. JENNY, H., and OVERSTREET, R., 1939. Cation exchange between roots and
soil colloids. Soil Sci. 47:257-72.
13. KRANTZ, B. A., OHLROGGE, A. J., and SCARSETH, G. D., 1943. Movement
of nitrogen in soils. Soil Sci. Soc. Amer. Proc. 8:189-95.
14. KURTZ, L. T., 1953. Soil and Fertilizer Phosphorus in Crop Nutrition, Chapter
HII. (Edited by W. H. Pierre and A. G. Norman.) Academic Press, Inc., New
York.
15. LEHR, J. R., BROWN, W. E., and BROWN, E. H. Chemical behavior of monocalcium phosphate monohydrate in soils. Submitted to Soil Sci. Soc. Amer.
Proc. for publication in 1957.
16. LYON, T. L., BUCKMAN, H. 0., and BRADY, N. C., 1952. The Nature and
Properties of Soils. The Macmillan Co., New York.
17. NELSON, L. B., and UBLAND, R. E., 1955. Factors that influence loss of
fall applied fertilizers and their probable importance in different sections of
the United States. Soil Sci. Soc. Amer. Proc. 19:492-96.
18. OLSEN, S. R., 1953. Soil and Fertilizer Phosphorus in Crop Nutrition, Chapter
IV. (Edited by W. H. Pierre and A. G. Norman.) Academic Press, Inc., New
York.
19. REED, J. F., 1953. Fertilizer Technology and Resources in the United States,
Chapter VIII. (Edited by K. D. Jacob.) Academic Press, Inc., New York. 20. REITEMEIER, R. F., 1951. Soil potassium. Advances in Agronomy (Edited
by A. G. Norman) Vol. 3, pp. 113-64. Academic Press, Inc., New York.
21. SLACK, A. V., 1955. Production and use of liquid fertilizers. Agri. and Food
Chem. 3:568-74.
22. VAN DER MAREL, H. W., 1954. Potassium fixation in Dutch soils. Mineralogical analyses. Soil Sci. 78:163-79.
JOHN T. PESEK and JOHN R. WEBB
Iowa State College
Chapter 3
Economic Interpretation of the Importance of
Water Solubility in Phosphorus Fertilizers
When Used as Hill Fertilizer for Corn'
HE phosphorus content of commercial fertilizers in the United
States is guaranteed according to the procedure for determining
available P205 of the Association of Official Agricultural Chemists
(1). The tacit assumption is made that if the phosphorus in a fertilizer is "available," according to the procedure, then the fertilizer is of equal value as a source of phosphorus to another source of the same composition determined in like manner. Manufacture and merchandising of fertilizer has been based on the above assumption, and consequently different fertilizers of the same legal grade actually may contain most of their phosphorus in widely differing chemical forms. To remain within the legal limits, the chemical form of the phosphorus may vary from compounds of very low water solubility such as tricalcium phosphate and dicalcium phosphate to the highly water-soluble monocalcium phosphates, ammonium phosphates, and others.
Much agronomic work has been supported by the Tennessee Valley Authority in connection with its development of various phosphorus fertilizer materials. The materials, which were tested, varied widely and were applied to many different crops and over a wide range of soil types, climatic conditions, and cultural practices. The results of these tests have been summarized from time to time by TVA agronomists. Seatz et al. (5) have pointed out the advantages and disadvantages of the fused tricalcium phosphate as a fertilizer and indicated its general range of use, while Tisdale and Winters (9) evaluated calcium metaphosphate in the same manner. Both of these materials are essentially water-insoluble and they were usually compared with concentrated superphosphate as the standard. The available PO, in the latter is approximately 90 to 95 percent water-soluble.'
First, Rogers (4) and later Thorne et al. (8) presented summaries of agronomic results with nitric phosphates (formerly and temporarily designated as "nitrophosphates") from all of the cooperating experiment
'The work reported in this chapter has been supported in part by two grants-in-aid from the Tennessee Valley Authority.
2 The water solubility or percent water-soluble refers to the percent of the neutral ammonium citrate soluble phosphorus in water-soluble form, both determined by the A.O.A.C. Method (1), and, in this chapter, will refer only to phosphorus unless specifically stated otherwise.
1. T. PESEK AND 1. R. WEBB
stations. Nitric phosphates are interesting materials for research because the different grades produced by various processes vary from I to over 40 percent water-soluble phosphorus (table 3.1). The conclusions in general were that the phosphorus in these materials was about equal in plant availability to that in concentrated superphosphate, particularly in the southeastern United States. According to Rogers (4) there was some evidence that higher water solubility appeared desirable in limited tests in Iowa and Nebraska. Conclusions of Thorne et al.
(8) were about the same but they noted that commercial fertilizers with low water-soluble phosphorus levels produced by other processes were just as inferior for some purposes as were the nitric phosphates of similar water solubility. More recently, Webb (10) has measured and reported highly significant advantages of fertilizers with a high percent of water-soluble phosphorus when used as hill fertilizers for corn. The evaluation was made on the basis of different vegetative response and yield increases caused by materials of varying water solubility of phosphorus.
Archer and Thomas (2) have reported that the water solubility of the phosphorus in commercial grades produced by selected plants varies widely from one grade and plant to another, and also some within grades. They also cited some of the factors which seemed to contribute to lowering of water solubility of the phosphorus and those which tended to maintain it at higher levels. Rogers (4) reported how nitric phosphates vary in water-soluble phosphorus percent and Hignett (3) presented data to show how the water solubility of phosphorus decreases upon ammoniation of both ordinary and concentrated superphosphate. Hignett (3) also indicated that it costs somewhat more to produce the same grade of fertilizer at higher levels of water-soluble phosphorus by current commercial processes.
Since the water solubility of phosphorus in hill fertilizers for corn plays an important part in their value and since there is a tendency for materials of higher water solubility to cost more, it seems appropriate to evaluate these factors within an economic framework. It is therefore the purpose of this chapter to investigate the functional relationships between percent water-soluble phosphorus and phosphorus rates in hill fertilizers for corn and how fertilizer recommendations may be influenced by possible price differentials due to water solubility of phosphorus.
SOURCE OF DATA AND PROCEDURE
The data utilized in this study were selected from a series of experiments designed to compare the effectiveness of phosphorus fertilizers in which the water solubility of the phosphorus varied. The experiments were conducted each year from 1952 to 1955 and the different sources of phosphorus used are presented in table 3.1. These experiments are described in detail elsewhere (10). Briefly, rates of 10 and
ECONOMICS OF SOLUBILITY
Table 3.1. Sources and Water Solubilities of Phosphates Used in the
Hill Fertilization Experiments From 1952 to 1955
Source of Phosphorus
Nitric phosphate (C02)a Aluminum nitric phosphate Aluminum nitric phosphate Nitric phosphate (IV)b Nitric phosphate (I)b Nitric phosphate (III) b Aluminum nitric phosphate Aluminum nitric phosphate Commercial type Nitric phosphate (II) b Nitric phosphate (I) b Concentrated superphosphate Concentrated superphosphate Ammo-phosphate' Diammonium phosphate Diammonium phosphate
Fertilizer Grade of P,05 Source
12-12-12 15-15-15
11-14-16 12-12-12 17-22-0
12-12-12 15-15-15 13-16-15 10-10-10
11-14-0 12-33-0
0-49-0 0-46-0 11-48-0 18-18-18
2 0-54-0
Percent Water-Soluble P205 in
1952 1953 1954 1955
2
4
5
10
14 14 14
16
43 43
92 93
100
aA commercial trial process.
bTVA process designation.
cA commercial material.
dEstimated.
20 or 15 and 30 pounds of P201 per acre with uniform levels of nitrogen and potassium were applied in the hill for corn at or shortly after planting. Uniformly high levels of nitrogen and potassium were also applied where needed to insure good yields.
Yield estimates were made and population counts at maturity were recorded. The experiments were analyzed by the method of covariance
(6) and mean yields adjusted to uniform plant density within each experiment. The mean treatment yields from all experiments showing a significant response to phosphorus were considered and used in this study.
The data from each year were pooled together because all experiments had the same fertilizer rates and sources, and were comparable in the number of replications. The data for each year were fitted with multiple regression equations of the general forms:
Y =bo + b1P + b2 p2 + bS + b, S2 + bPS
Y = b, + bP + b2P2 + b3S + b4 S2
Y is the estimated yield, b0 the intercept, 'b, through b5 the regression
(3.1) and (3.2)
where
coefficients, P the rate of available P205 per acre applied, and S the percent water solubility of the phosphorus in the fertilizer.
The equations were selected because they represent the simplest types which would express curvilinear effects in both variables and, in case of equation 3.1, the interaction effects as well. It is well known that response to fertilizer rates usually follows the law of diminishing returns, and it was assumed that response to water solubility would do likewise because an increase in water solubility is basically an increase in rate of water- soluble P205 applied at a fixed rate of available P205. A rough plot of the data also showed that a curvilinear relationship between yield response and water solubility was likely.
RESULTS AND DISCUSSION
The equations which were fitted to the pooled data are presented by years in table 3.2. An examination of these equations indicates that the equations for 1952 differ from the rest in that the second derivative of Y with respect to P is positive. This means that for that year there was an increasing return rather than a diminishing return from fertilizer use within the range of the experimental treatments. The reason for this is of agronomic interest and will not be considered in this chapter. Equations for the last three years all showed a diminishing return to scale with respect to both rates and water solubility of phosphorus.
Table 3.3 presents the multiple correlation coefficients, t values and probabilities associated with the eight equations in table-3.2. The
Table 3.2. Equations Expressing the Estimated Yield, Y, As a Function of Rate of
P 05 in the Hill, P, and the Percent Water Solubility, S
Form of
Year Equation Algebraic Expression
1952 (3.1) Y = 85.3 - .0336 P + .00701 p2 +.135S - .000909S2 + .000418PS
(3.2) Y = 85.3 - .0384 P + .00756p2 +.143S - .00090892
1953 (3.1) Y = 52.6 + .373 P - .077 8p2 +.122S - .00105S2 + .00193PS
(3.2) Y = 52.6 + .285 P - .00427p2 +.165S - .00105S2
1954 (3.1) Y = 66.9 + .251 P - .00127 p2 + .228S - .00137S2 + .000112PS
(3.2) Y = 66.8 + .244 P - .000983p2 + MIS - .001379'
1955 (3.1) Y = 57.6 + .959 P - .0278p2 + 141S - .00063OS2 + .00136PS
(3.2) Y = 57.6 + .877 P .0228P2 + .161S - .000630e
1952 Aa (3.1) Y = 77.6 + 1. 12 P .02 64 p2 - .333S + .00178S2 + .00803PS
(3.2) Y = 77.6 + .658 P -.00807 p2 - .153S + .00178S2
1952 B b (3.1) Y = 100.7 - .198 P + .014 5p2 + .0968S - .0000284S2 - .00307PS
(3.2) Y = 100.7 - .0219 P + .00747 p2 + .0277S - .0000280S'
'Experiments with decreasing return to scale with respect to rates. b Experiments with increasing return to scale with respect to rates.
J. T. PESEK AND J. R. WEBB
ECONOMICS OF SOLUBILITY
Table 3.3. Multiple Correlation Coefficients and t - Values for
Regression Equations Presented in Table 3.2
Year and t - Values for the Coefficients Number of
Equation R b,1 b b3 b4 b5 Experiments
1952 (3.1) .336 0.04 0.27 0.42 0.37 0.06 6
1952 (3.2) .334 0.04 0.25 0.45 0.36 6
1953 (3.1) .8834* 2.77** 2.Ola 2.54* 2.784* 1.56b4 1953 (3.2) .873*4 2.28* 1.33 b 4.l4** 2.73** 4
1954 (3.1) .8944* 1.05c 0.18 3.03* * 2.28* 0.07 3
1954 (3.2) .894* * 1.l7c 0.18 3.63** 2.32* 3
1955 (3.1) .941** 3.464* 2.42* 2.40* 1.35b 0.79d 2
1955 (3.2) .940*4 3.444* 2.39* 3.08** 1.35b 2
1952 (3. 1)A .406 1.05c 0.866 0.87d 0.61 0.91 d 4
1952 (3.2)A .373 0.70 0.35 0.47 0.61 4
1952 (3.lI)B .273 0.11 0.27 0.14 0.01 0.20 2
1952 (3.2)B .267 0.01 0.19 0.05 0.01 2
Probabilities: ** .01; ~= .05; a . 1 to .05; b = .2 to . 1; c = .3 to .2; 6= .5 to .4.
information shows that the type of equation used gives a very poor fit for the data in 1952, but that the equations for the other years represent fits which would be considered good for this type of work. In all of the last three years the coefficient of determination is at least as high as 0.76 and indicates that the selected regressions accounted for a large part of the differences among treatments which were observed. For 1952, the coefficient of determination was only 0.11 which is very low and unsatisfactory. In order to ascertain the reason for such poor fits, the data for 1952 were reexamined. This revealed that four experiments indicated a decreasing return and two an increasing return from increasing rates of fertilizer applied. The latter experiments were the greater responders, and their effect offset the smaller response and decreasing return to scale of the other four experiments. This is why the original equations for 1952 in table 3.2 indicate an increasing return to scale. In an effort to overcome this, regressions were computed separately for the two groups of experiments with different response characteristics and these equations also appear in table 3.2 with the pertinent R and t values in table 3.3. An examination of the results indicates that little was gained and that those regressions showing decreasing returns to scale for rates of P205 show increasing returns to scale for water solubility and vice versa.
It is evident that the simple second order regressions with two independent variables are inadequate and that possibly a cubic or even higher order equation would be necessary. Since the exact fitting of the data was originally outside of the scope of this study and the data from the other years agree very closely, it was decided to develop this chapter without the data for 1952. It is felt that the general conclusions will
1. T. PESEK AND J. R. WEBB
not be altered, however, a more thorough agronomic study of these data is needed.
In view of the difficulty with the data of 1952, some question might arise with regard to the fit obtained for the other years. The R and t values in table 3.3 give some estimate of the precision with wfilch t&e regressions express the relationships observed, and the fact that the equations selected are in agreement with the generally accepted concept of response curves and surfaces provides further confidence in the regressions in table 3.2. A further test would be to compare certain predictions obtained by these equations with the equation of Spillman
3
(7). One of the comparisons is the maximum predicted response and these comparisons are made in table 3.4. Spillman values were calculated using the response to the two rates of P2 0, for each source of phosphorus independently. Hence the standard error of these values may be assumed to be considerably greater than that of the values obtained from the multiple regression equation 3.1.
There is remarkably good agreement between the predicted yields by the two equations especially in 1953 and 1955. Agreement is also good for the materials of high water solubility in 1954, but agreement is somewhat poorer with less soluble materials. The reason for this is that while, with only one exception, maximum estimated yields in 1953 and 1955 occurred within the experimental rates of application, the maximum predicted yields in 1954 were estimated to occur far beyond the highest rate of 30 pounds of PO, per acre applied. It is not surprising, then, that agreement was not as good in 1954. The explanation of why this occurred is an agronomic problem, and for purposes of this study it will be assumed that this behavior is real and does occur from time to time. On the additional basis of good agreement with certain parameters of a generally accepted equation (Spillman or Mitscherlich) it is again concluded that the equations which were selected correctly reflect the relationships which existed.
Once the relationship of yield to the water solubility and rate of
phosphorus has been established, it is possible to answer several questions about the economy of using these different fertilizers. It would be interesting to know what the optimum rate of hill fertilizer would be under the experimental conditions.
To calculate the optimum rate of Z 05 it will be assumed that either:
(a) the rate of nitrogen and potassium is a constant, as it was in these experiments, and therefore represented a fixed cost similar to cost of application or cultivation, or (b) no nitrogen or potassium was applied. In the latter case the "fixed cost" of nitrogen and potassium would be zero. Either assumption will lead to the same solution and will give the number of pounds of P205 necessary to maximize profit (or minimize loss in case fixed costs, i.e., cost of needed nitrogen and potassium, and application costs, exceed profit from use of phosphorus). It is
'The Spillman and Mitscherlich equations trace the same curves when plotted; however, since the Spillman form has some advantages in certain calculations, this form was used.
Table 3.4. The Maximum Predicted Yield Increases in Bushels Per Acre and Rate
of P20, at Maximum As Computed From Equation 3.1 for 1953, 1954,
and 1955, and the Maximum Predicted Yield by the Spillman Equation 3.7
Percent 1953 1954 1955
Water Max. Yield Incr. Lbs. P205 for Max. Yield Incr. Lbs. P205 for Max. Yield Incr. Lbs. P205 for
Solubility Eq. 3.1 Spillman Max. Yielda Eq. 3.1 Spillman Max. Yielda Eq. 3.1 Spillman Max. Yielda
100b 19.5 19.5 103.5 18.3 19.6 19.3
100b 18.3 20.0 19.2
93 22.8 19.3 103.2 18.1 17.6 18.0
92 12.0 11.0 35.4
43 10.0 10.2 29.3 20.2 12.1 101.0
34 13.2 10.9 17.9
33 13.1 13.6 17.9
28 8.4 8.0 27.4
16 11.2 11.2 17.6
14 6.6 8.0 25.7 15.6 12.8 99.7
10 9.4 11.7 17.4
5 5.3 5.5 24.6
4 8.6 8.3 17.3
2 12.9 4.7 99.2
' Calculated by equation 3.1.
bSources were diammonium- and monoammonium-phosphate, respectively.
J. T. PESEK AND 1. R. WEBB
further assumed that the response observed in the data is a true response to phosphorus and does not represent an interaction effect with other nutrients in the fertilizer. Agronomically, this may not be the case because phosphorus often interacts with nitrogen. The data used cannot be made to make the distinction, so only a phosphorus effect must be assumed. The optimum rate of R 05 is given by equating the PO,:corn price ratio to the partial derivative of yield with respect to the rate of P205, When the partial derivatives dY/dP, of equations 3.1 and 3.2 are taken the following equations result:
(3.3) dY/dP = b, + 2b2P + b5S
and
(3.4) dY/dP = b, + 2b2P
respectively.
In equation 3.4 it is apparent that the solution will lead to a value which is independent of the water solubility. That is, the optimum rate Of P20, and corn will be the same whether the water solubility is 0 or 100 percent. On the other hand, the solution involving equation 3.3 involves water solubility of phosphorus and, therefore, the optimum rate will vary with the solubility. If the sign of the coefficient of S in this equation is positive, i.e., the sign of the coefficient of the PS term in equation 3.1 is positive, the optimum rate of P205 will be higher for the more soluble sources of phosphorus. When the sign is negative the reverse will be true.
In table 3.5 are presented selected solutions for optimum rates of
P20, at specified P205:corn price ratios. The general relationship indicates that the optimum rates of P2Q decrease as the percent water solubility decreases and this results from the positive sign of the coefficient of PS in the equations listed in table 3.2. The larger the absolute value of the coefficient of this term, the greater the effect water solubility has on the optimum rate, hence the small relative effect from 59.6 pounds per acre to 64.0 pounds in 1954 and the greater effect ranging from 17.5 to 29.9 pounds in 1953. The expected yield increase is also greater with higher water solubility and the profit per acre also greater. Take for example the 0 and 100 percent water solubility in 1953. With the price of P205 at 10 cents per pound and corn at $1.00 per bushel (P /P = .10) the profit is $11.60 - 2.99 = $8.61 at 100 percent water so lity but only $4.20 - 1.75 = $2.45 at 0 water solubility. Other comparisons are not as extreme but important to remember in making decisions regarding fertilizer use.
In passing, it should be pointed out that as the relative price of corn increases (i.e., the Pp/Pc decreases) it is profitable to apply more PD5 and this results in increased yields. Profit is also increased. It was shown above that the profit at 100 percent water solubility in 1953 was $8.61 per acre with P205 at 10 cents per pound and corn at $1.00 per bushel. With the price of P20, decreasing to 5 cents per pound and
Table 3.5. Optimum Rates of P20 and Estimated Increases in Yield of Corn for
Specified Price Ratiosa of P205 to Corn (Pp/Pc) for Phosphorus Materials of Different Water Solubility
Percent Equation 1953, 3.1 Equation 1954, 3.1
Water Pp/Pc = .10 Pp/Pc = .05 Pp/Pc = .10 Pp/Pc = .05
Solubility Lbs. P205 Incr. Lbs. P205 Incr. Lbs. P205 Incr. Lbs. P205 Incr. 100 29.9 11.6 33.2 11.9 64.0 20.7 83.7 22.2
80 27.5 11.5 30.7 11.9 63.1 20.8 82.8 22.3
60 25.0 10.9 28.2 11.1 62.2 19.9 82.0 21.4
40 22.5 9.4 25.7 9.6 61.3 17.8 81.1 19.3
20 20.0 7.1 23.2 7.4 60.5 14.7 80.2 16.2
0 17.5 4.2 20.8 4.4 59.6 10.4 79.3 11.9
aThe price ratio is taken as the price per pound of P205 to the price of a bushel of corn.
Equation 1955, 3.1
PP/Pc = . 10 PP/Pc = .05
Lbs. P205 Incr. Lbs. P205 Incr.
17.8 18.5 18.7 18.6
17.4 17.4 18.3 17.5
16.9 15.7 17.8 15.9
16.4 13.7 17.3 13.8
15.9 11.2 16.8 11.3
15.4 8.2 16.3 8.3
corn remaining the same (Pp/P, = .05), the profit becomes $11.90
- $1.66 = $10.24 per acre.
If calculations are based on equation 3.2 form without a PS term, the optimum rate of P201 will be the same for any Pp/P, ratio regardless of the water solubility. The optimum rates of P2O for certain Pp/PC ratios are presented in table 3.6 together with the expected yield responses for materials with different levels of water solubility. As was the case in table 3.5 above the higher the water solubility, the higher the expected response and profit and the lower the FP /Pc ratio, the higher the optimum rate of P2 05 and the higher the profit.
In general the optimum rates are within the range of optimum rates calculated by the form of equation 3.1 with the possible exception of 1954 at low Pp/Pc ratios where estimates are somewhat higher. Predicted responses also agree well with the exception of estimates at high water solubility in 1955. It should be pointed out that perfect agreement cannot be expected because the two forms of the equations are somewhat different. There seems to be some basis for a logical choice of one form of equation over the other, however, and the choice would be for equation 3.1. The reason is that an interaction between water solubility and rate should exist because as water solubility decreases, the available phosphorus for plant growth does not decrease proportionately. If the availability of water-insoluble phosphorus is expressed in terms of the availability of the water-soluble part it becomes apparent that at a given rate, more and more of the plant available phosphorus will come from the water-insoluble part as water solubility decreases. Hence, while a given rate of 100 percent water-soluble phosphorus provides, for example, 100 units of available phosphorus, the same rate of 50
Table 3.6. The Optimum Rates of P O at Selected Pp/Pc Ratiosand the Expected Increases in Yield at Certain Levels of Water Solubility of the Phosphorus.
Calculations Are Based on Equations 1953, 3.2; 1954, 3.2; and 1955, 3.2
Equations
1953,3.2 1954,3.2 1955, 3.2
P'/PC Pp/pc P71/PC
.10 U5 .10 05 JU U5
Optimum rate
Of P 05 21.7 27.5 73.1 98.6 17.0 18.1
Percent water
solubility Estimated Increase in Bushels per Acre
100 10.2 10.6 21.9 23.8 24.4 24.5
80 10.6 11.1 22.2 24.2 21.2 21.3
60 10.3 10.7 21.5 23.4 18.0 18.1
40 9.1 9.5 19.6 21.5 14.8 14.9
20 7.1 7.5 16.6 18.5 11.5 11.6
0 4.2 4.6 12.6 14.5 8.3 8.4
1. T. PESEK AND 1. R. WEBB
Rate of P205 Equation 3.1 for Equation 3.2 for
in Lbs. per Acre 1953 1954 1955 1953a 1954a 1955a
10 67 83 123 78 84 128
20 76 84 133 78 84 128
30 85 85 144 78 84 128
'The absence of P in the first derivative makes the water solubility percent for maximum yield independent of the rate Of P205percent water- soluble phosphorus will supply more than 50 units, and that of 0 percent water solubility will provide some available phosphorus as well. This is apparent from tables 3.5 and 3.6 which predict reasonable increases in yield even with materials with no water solubility. It is felt that these figures are not artifacts of extrapolation because table 3.1 indicates that in each of the three years analyzed, materials close to 0 percent water solubility were included in the experiments. It is realized that the statistical data present in table 3.3 do not bear out this point of view as strongly as would be desired in all cases. But it must be remembered that the interaction effect is measured with more difficulty than the other effects and that these experiments were not designed specifically for evaluation of the interaction nor even to measure it with a relatively high level of efficiency.
One way to estimate the level of water solubility which should be incorporated into fertilizers used as hill fertilizer for corn is to determine the percent water solubility at which the maximum yield increase for a given rate is obtained. This is done by equating the first partial derivative of yield with respect to water solubility (dY/dS) to zero and solving for the maximum. The resulting equations based on equations 3.1 and 3.2 are
(3.5) dY/dS = b, + 2bS + bP
and
(3.6) dY/dS = b, + 2bS
respectively. The results are presented in table 3.7 and indicate that high water solubility is definitely an advantage. As a matter of fact 100 percent water solubility is not high enough according to equations 3. 1, 1955 and 3.2, 1955. In this year as well as in 1954, materials of 100 percent water solubility were included in the experiments and, therefore, there is a high degree of confidence in the prediction that at least 100 percent water-soluble phosphorus may be needed under certain conditions for maximum yields when it is used in a manner similar to that in the experiments. The highest level of water solubility in 1953 was
ECONOMICS OF SOLUBILITY
Table 3.7. Percent of Water-Soluble P205 at Which Maximum Yields
Are Reached in 1953, 1954, and 1955 As Estimated by
Two Forms of the Regressions Used
1. T. PESEK AND J. R. WEBB
92 percent and this may have been partly responsible for the lower estimated level of water solubility needed to attain maximum yields at a fixed rate of phosphorus. One interesting result of choosing an equation with an interaction (PS) term is the prediction that as lower rates of P2 0. are applied, lower water solubility should also be used. This is most pronounced ' in 1953, and it so happens that the coefficient of the interaction term in that year had the highest level of probability observed. An explanation of this relationship is reserved for an agronomic study.
It is concluded above that at the same price for water-insoluble (but citrate- soluble) and water-soluble P205 it is advantageous to have up to 100 percent water solubility when using the fertilizer in the hill for corn. However, Hignett (3) has shown that it costs more to produce mixed fertilizers of the same grade with higher degrees of water solubility. The problem now becomes somewhat different since water solubility has a cost and the higher the water solubility, the greater will be the cost per unit of P205- Consequently, the ratio Pp/Pc will vary depending upon the water solubility of the phosphorus in the fertilizer which is used and becomes necessary to obtain the relationship between the price and water solubility.
To relate price to water solubility it is first necessary to estimate cost of producing a particular material. Hignett (3) estimated cost of producing 3-12-12 at $40.55 per ton with 23 percent water solubility and $41.30 per ton with 65 percent water solubility. The cost of producing 5-20-20 is $62.74 at 50 percent water solubility and $64.50 per ton at 75 percent water solubility. Allowing an arbitrary 10 percent profit on each to manufacturer and to dealer the prices for 3-12-12 to the farmer would be $49.07 and $49.97 per ton respectively for 23 and 65 percent water-soluble phosphorus material. Likewise the price of 5-20-20 would be $75.91 and $78.05 per ton for 50 and 75 percent soluble material.
The cost, C, of the P205 with the associated nitrogen and potassium 4 may be expressed in terms of water solubility by a simple linear equation such as
(3.7) C = n + ms
where n and m are coefficients determined by the prices used. By assuming that the function is continuous between the 23 and 65 percent points the equation for the 3-12-12 is obtained by substituting the cost per pound of P205 (with the nitrogen and potassium) and the percent
4 The price of fertilizer is used in this ratio instead of the price of phosphorus. This is necessary because each unit Of P205 is associated with .25 unit of nitrogen and one unit of K20 which cannot be separated. When more phosphorus is applied more of the others are applied as well. For the purpose studied, this ratio of elements is a good one on many Iowa soils. This does not preclude the possibility that lower cost ratios may be found and that different ratios might offset the level of water solubility desired or vice versa. This is another study and cannot be made with the data on hand.
ECONOMICS OF SOLUBILITY
water solubility into equation 3.7 and solving simultaneously for n and m. This leads to the cost of water solubility of
(3.8) C .2025 + .0000881S
for the 3-12-12, and
(3.9) C .1792 + .000212S
for the 5-20-20.
To find the optimum level of water solubility, it is necessary to
equate the first partial derivative of yield with respect to percent water solubility (dY/dS) for any response function to the first derivative of the cost with respect to solubility (dC/dS) and solve. Taking the first derivative of equation 1955, 3.2 and equating it to the first derivative of equation 3.8, equation 3.10 is derived.
(3.10) .161 - .00126S = .0000881
Solving for S a figure of 121 percent solubility is secured, or for practical purposes 100 percent. Using equation 1953, 3.2 a figure of 78 percent water solubility is secured, which is the same as the tabular value for maximum solubility desired in table 3.7. This serves to emphasize the relatively insignificant cost of increasing the water solubility on the basis of the available information.
The solution is slightly different when the equation has an interaction term such as equation 1955, 3.1. Equating dY/dS of this equation to dC/dS of equation 3.8, equation 3.11 is derived.
(3.11) .141 - .00126S + .00136P = .000081
Solving for S in equation 3.12,
(3.12) S = 111 + 1.09 P
the rate of 30 pounds of PO, is obtained, the optimum solubility is 144 percent, or again at least 100 percent. Practically, dC/dS is vanishingly small and does not affect the result. Even for the 5-20-20 dC/dS is only .000212 and will not alter the results at the three significant figures justified by the data. These results indicate that it would be economical for users to pay the difference in cost necessary to produce phosphorus fertilizers of high water solubility as estimated by Hignett (3).
ECONOMIC INTERPRETATIONS
It has been shown that it is possible to apply economic principles to satisfactory data on the effect of water solubility of phosphorus on corn
1. T. PESEK AND 1. R. WEBB
yields. In this study the multiple quadratic equation with two independent variables was fitted to summarized data for three separate years. One form of the equation also contained a cross product term allowing for the interaction of water solubility and rate of application.
The economically optimum rates of P205 were calculated for various P205:corn price ratios and the expected yields at the optimum fertilizer rate were estimated. The lower the Pp/P, ratio the greater were the optimum rates, expected responses, and estimated profits.
Water solubility of phosphorus is important in not only determining the optimum rate Of P205 but in affecting expected yields and profits. By using materials of low water solubility, it is possible to lose by
(a) not getting the best response from the P205 used, or (b) by utilizing less per acre than would be optimum at higher water solubility.
The small increase in cost of producing fertilizers with higher
water solubility is offset by the higher returns when used as hill fertilizers for corn. It is possible that extra cost of high water solubility could affect the optimum water solubility with higher increases in cost than those used in this study.
REFERENCES CITED
1. Association of Official Agricultural Chemists, 1955. Methods of Analysis, 8th edition.
2. ARCHER, J. R., and THOMAS, R. P., 1956. Water-soluble phosphorus in fertilizer. Agricultural and Food Chemistry 4:608-13.
3. HIGNETT, T. P., 1956. Technical and economic factors involved in production of fertilizers of high water-soluble P 05 content by conventional processes.
Commercial Fertilizer 92: No. 5., 23-26, and 67.
4. ROGERS, H. T., 1951. Crop response to nitrophosphate fertilizers. Agronomy Journal 43:468-76.
5. SEATZ, L. F., TISDALE, S. L., and WINTERS, ERIC, 1954. Crop response to fused tricalcium phosphate. Agronomy Journal 46:574-80.
6. SNEDECOR, G. W., 1946. Statistical Methods, Iowa State College Press.
7. SPILLMAN, W. 1., 1933. Use of the exponential yield curve in fertilizer experiments. USDA, Tech. Bul. 348.
8. THORNE, D. W., JOHNSON, P. E., and SEATZ, L. F.2 1955. Crop response to phosphorus in nitric phosphates. Agricultural and Food Chemistry 3:136-40. 9. TISDALE, S. L., and WINTERS, ERIC., 1953. Crop response to calcium metaphosphate on alkaline soils. Agronomy Journal 45:228-34.
10. WEBB, J. R., 1955. Significance of water solubility in phosphate fertilizers.
Ag. Chem. 10:(3) 44-46.
T. P. HIGNETT
Tennessee Valley Authority
Chapter 4
Technical and Economic Factors involvedd in
Production o/ Fertilizers ot High Water-Solubte
P 0 Content by Conventional Processes
2 5
HE effect of the water solubility of phosphorus in fertilizers has
been a subject of many agronomic experiments. These experiments have shown that under certain conditions the crop yield was increased by increasing the solubility of phosphorus in the fertilizer. Under other conditions, crop yields were not affected by the water solubility of the phosphorus in the fertilizer.
It seems appropriate to examine the relative costs of producing
fertilizers of various degrees of water solubility and to compare these costs with their relative value for crop production. In Chapter 3, Dr. Pesek presents a study of the relationship between the phosphorus solubility and the value of fertilizers for certain specific uses. A comparison is shown of the cost of producing certain grades of fertilizer by formulations that would provide different levels of water solubility ranging from about 20 to 80 percent. The cost comparisons will be restricted to fertilizers produced in a typical manufacturing plant from conventional raw materials. The formulations used will be those that have been shown by experience to be suitable for production of fertilizers of satisfactory physical properties.
The term "water-soluble P205" as used in this chapter refers to the amount of P205 dissolved in an A.O.A.C. (1) analytical procedure. In this procedure a 1-grarn sample is placed on a filter paper and washed with successive small portions of water until 250 milliliters of filtrate is collected. Vacuum filtration is used, if necessary, to complete the washing in one hour. The term "water solubility" of the phosphorus content of fertilizers refers to the percentage of the available P205 content that is water soluble, as determined by A.O.A.C. procedures.
The A.O.A.C. water-washing procedure originally was intended to remove the readily soluble phosphorus compounds from superphosphate in preparation for extraction with neutral ammonium citrate solution. No determination of the amount of phosphorus dissolved by the waterwashing procedure is required in the course of determining available 1320 , and such determinations are seldom made in commercial practice. However, the method seems fairly satisfactory for separating the readily soluble compounds, ammonium phosphates and monocalcium phosphate, from the relatively insoluble phosphorus compounds in most conventional fertilizers. The method should be re-examined if it is to be used for evaluation of the quality of commercial fertilizers.
T. P. HIGNETT
At present, no guarantee of the water-soluble P205 content of fertilizers is required, and usually none is made. Most manufacturers do not determine the water-soluble P205 content of their products. In view of the importance of water solubility for some fertilization practices, it appears that some method of recognizing and reporting water solubility is needed.
Most commercial ferti.100
o lizers derive their phosphor- us content from ordinary or
jU triple superphosphate or
-J
< 80 mixtures of these materials.
-j
< Ammoniation of the super,4 phosphates is an almost uni0 60 versal step in producing
grades containing both nitrogen and phosphorus. Ammo0 40 niation is an economical
_ means of supplying nitrogen, 0, and it is a necessary step in
D most granulation processes.
0 20OC
Uo In many cases it would be
difficult to produce high< __ 1 analysis grades of satisfactory
0 2 4 6 8 10 physical properties from conDEGREE OF AMMONIATION, ventional raw materials withLB. FREE NH3/UNIT AVAIL P205 out ammoniation.
Ammoniation of superFig. 4.1 - Effect of degree of ammoniation on phosphates results in a series water solubility of P205 in ordinary superphos- of chemical reactions by
phate. which monocalcium phosphate
is converted to ammonium
phosphates which are water-soluble and dicalcium phosphate and other more basic calcium phosphates which are water-insoluble. Figure 4.1 shows the effect of the degree of ammoniation on the water solubility of PD25 in ordinary superphosphate. These data were obtained in a TVA pilot-plant study of ammoniation of superphosphates as a step in the production of mixed fertilizers. The maximum practical degree of ammoniation in commercial processes is between 6 and 7 pounds of free ammonia per unit of P205 in ordinary superphosphate. This degree of ammoniation reduces the water solubility of the P205 from about 20 to 25 percent. Since ammonia or ammoniating solutions are the cheapest forms of nitrogen available to fertilizer manufacturers, most manufacturers try to achieve a high degree of ammoniation when producing high-nitrogen grades.
Figure 4.2 shows the effect of the degree of ammoniation on the
water solubility of P205 in triple superphosphate. The minimum water solubility obtained was about 50 percent at 2.5 to 3.8 pounds of free ammonia per unit of P205. Higher degrees of ammoniation tended to
FACTORS IN PRODUCTION OF P205 FERTILIZERS
increase the water solubility because some of the dicalcium phosphate reacted with ammonia to produce tricalcium phosphate or hydroxyapatite and diammonium phosphate.
" 2 3 4 5 6
DEGREE OF AMMONIATION, LB. FREE NH3/UNIT AVAIL. P205
Fig. 4.2 - Effect of degree of ammoniation on water
solubility of P205 in concentrated superphosphate.
The data of figure 4.2 are for ammoniation of straight triple superphosphate with anhydrous ammonia. Several tests were made in which a 10-20-20 fertilizer was made by ammoniation of mixtures of triple superphosphate, potassium chloride, and sulfuric acid with ammonia ammonium nitrate solutions. The degree of ammoniation varied from 3.5 to 4.3, and the water solubilities varied between 60 and 70 percent; these solubilities are somewhat higher than the curve in figure 4.2. The reason for this difference is not known.
The water solubility of P205 in mixed fertilizers may be decreased by inclusion of basic materials other than ammonia. Limestone, dolomite, and calcium cyanamide are examples of basic materials that may be added to mixed fertilizers which may decrease the water solubility. Fertilizers in which the water solubility of the P205 content is less than 20 percent may be made by heavy ammoniation of superphosphate plus the addition of limestone or other basic materials.
A survey of the water solubility of phosphorus in mixed fertilizers in 1949-1950 was reported by K. G. Clark and W. M. Hoffman (2). The water solubility of mixed fertilizers varied from 3 to 100 percent and averaged about 50 percent.
T. P. HIGNETT
Table 4.1. Formulations and Costs for 3-12-12
23% of P205 65% of P205
in a Water- in a WaterPrice Soluble Form Soluble Form
$ per Lb. per $ per Lb. per $ per Raw Material Grade Ton Ton Ton Ton Ton
Ordinary superphosphate 20% P205 20.00 1224 12.24 1224 12.24 Ammonia 82% N 90.00 75 3.38 -
N solution X 40.8 % N 57.00 - - 150 4.28
Potassium chloride 60% K20 34.00 408 6.94 408 6.94
Filler - 4.00 293 0.59 218 0.44
2000 23.15 2000 23.90
Operating cost and
overhead 7.70 7.70
Bags 3.00 3.00
33.85 34.60
Sales cost (10 cents
per unit) 2.70 2.70
36.55 37.30
Freight (100 mi.) 4.00 4.00
Delivered cost 40.55 41.30
Delivered cost per unit (1.50) (1.53)
Price to dealer 46.00 46.00
Profita 5.45 4.70
'Before corporation income taxes.
Formulations and Costs for 1-4-4 Fertilizers
Formulations and costs for typical mixed fertilizers were calculated using raw material costs that were believed to be typical of a midwestern location. The most common 1-4-4 ratio grades are 3-12-12 and 5-20-20. Two formulations for 3-12-12 are shown in table 4.1 One formulation uses anhydrous ammonia for ammoniation; the other uses a typical ammoniating solution containing 21.7 percent free ammonia, 65 percent ammonium nitrate, and 13.3 percent water. When anhydrous ammonia is used, the degree of ammoniation is about 6.2 pounds of free ammonia per unit of R~ Q and the resulting water solubility of the phosphorus content is about 23 percent (figure 4.1). When the ammoniating solution containing 21.7 percent free ammonia is used, the degree of ammoniation is 2.7 and the water solubility is 60 percent. The difference in cost between these two formulations is only 75 cents per ton which is less than 2 percent of the price to dealers. However, this cost difference is equivalent to 14 percent of the manufacturer's profit.
50% of P205 75% of P205
in a Water- in a WaterPrice Soluble Form Soluble Form $ per Lb. per $ per Lb. per $ per Raw Material Grade Ton Ton Ton Ton Ton
Ordinary superphosphate 20% P20s 20.00 297 2.97 192 1.92 Triple superphosphate 467 P205 58.00 758 21.98 803 23.29 Ammonia 82%N 90.00 125 5.63 -
N solution Y 40.8% N 57.00 - - 250 7.13
Sulfuric acid 660 Be 20.00 140 1.40 140 1.40
Potassium chloride 60% K20 -34.00 680 11.56 680 11.56 2000 43.54 2065 45.30
Operating cost and
overhead 7.70 7.70
Bags 3.00 3.00
54.24 56.00
Sales cost (10 cents
per unit) 4.50 4.50
58.74 60.50
Freight (100 mi.) 4.00 4.00
Delivered cost 62.74 64.50
Delivered cost per unit (1.39) (1.43)
Price to dealer 71.00 71.00
Profit 8.26 6.50
aBefore corporation income taxes.
If limestone were used as a filler, the water solubility might be decreased below 20 percent. The effect on cost would depend on the relative cost of limestone and other filler materials.
Formulations and costs for 5-20-20 are shown in table 4.2. This grade is one that is usually produced in granular form. The formulations shown are known to be satisfactory for granulation by commonly used processes. The formulation that uses anhydrous ammonia is the cheaper and the more satisfactory for granulation. The degree of ammoniation is 3.9, and the water solubility of the P20r content is about 50 percent, as determined experimentally (3). In the formulation that uses an ammoniating solution containing 26 percent free ammonia, the degree of ammoniation is about 1.0 and the water solubility is about 75 percent. Use of an ammoniating solution containing only 21.7 percent free ammonia in this formulation would decrease the degree of ammoniation to about 0.5 and would increase the water solubility to about 85 percent (figure 4.2); the cost would not be affected appreciably. The difference in cost between the two formulations shown in table 4.2 is $1.76 per ton, or about 2.5 percent of the price to dealers. However, this difference is equivalent to 21 percent of the manufacturer's profit.
FACTORS IN PRODUCTION OF PO, FERTILIZERS
Table 4.2. Formulations and Costs for 5-20-20
2 3 %of P205 40% of P205
in a Water- in a WaterPrice Soluble Form Soluble Form $ per Lb. per $ per Lb. per $ per Raw Material Grade Ton Ton Ton Ton Ton
Ordinary superphosphate 20% P205 20.00 1020 10.20 1020 10.20 N solution X 40.8% N 57.00 500 14.25 397 11.31
Ammonium sulfate 21%N 48.00 - - 200 4.80
Sulfuric acid - 20.00 120 1.20 120 1.20
Potassium chloride 60% K20 34.00 340 5.78 340 5.78
Filler 4.00 100 0.20 -
2080 31.63 2077 33.29
Operating cost and
overhead 7.70 7.70
Bags 3.00 3.00
42.33 43.99
Sales cost (10 cents
per unit) 3.00 3.00
45.33 46.99
Freight (100 mi.) 4.00 4.00
Delivered cost 49.33 50.99
Delivered cost per unit (1.64) (1.70)
Price to dealer 60.30 60.30
Profit a 10.97 9.31
'Before corporation income taxes.
Comparison of tables 4.1 and 4.2 shows that the most economical way to increase the water solubility of a 1-4-4 ratio fertilizer is to increase the grade. Comparison of the more economical formulations for 3-12-12 and 5-20-20 shows that the delivered cost for 5-20-20 is less per unit of plant food ($1.39 versus $1.50/unit) and that the water solubility is higher (50 versus 23 percent).
Formulations and Cost for 1-1-1 Ratio Fertilizers
Two important grades of 1-1-1 ratios are 10-10-10 and 12-12-12. These grades are often produced as granular fertilizers; the formulations considered are suitable for granulation.
Two formulations for 10-10-10 are shown in table 4.3. Ordinary superphosphate is the only source of P205 in both formulations. In the first case, all of the nitrogen is supplied from ammoniating solution; the degree of ammoniation is about as high as is practical (6.8 percent), and the water solubility is about 23 percent (3). In the second formulation, the degree of ammoniation is decreased to 4.8 by deriving some of the nitrogen from ammonium sulfate and thereby decreasing the amount
T. P. HIGNETT
Table 4.3. Formulations and Costs for 10-10-10
50% of P205 75 %of P205
in a Water- in a Water
Price Soluble Form Soluble Form
$ per Lb. per $ per Lb. per $ per Raw Material Grade Ton Ton Ton Ton Ton
Ordinary superphosphate 20% P205 20.00 513 5.13 147 1.47 Triple superphosphate 46% P205 58.00 311 9.02 467 13.54 N solution X 40.8% N 57.00 500 14.25 308 8.78
Ammonium sulfate 21%N 48.00 200 4.80 567 13.61
Sulfuric acid 66P Be 20.00 150 1.50 150 1.50
Potassium chloride 60 % K20 34.00 406 6.90 406 6.90
2080 41.60 2045 45.80
Operating cost and
overhead 7.70 7.70
Bags 3.00 3.00
52.30 56.50
Sales cost (10 cents
per unit) 3.60 3.60
55.90 60.10
Freight (100 mi.) 4.00 4.00
Delivered cost 59.90 64.10
Delivered cost per unit (1.66) (1.78)
Price to dealer 73.70 73.70
Profita 13.80 9.60
aBefore corporation income taxes.
of ammoniating solution. The water solubility of the P201 content is about 40 percent (figure 4.1). The product of lower solubility costs $1.66 per ton less. Producing the material of higher solubility would decrease the manufacturer's profit by 15 percent.
Two formulations for 12-12-12 are shown in table 4.4. Since
12-12-12 derives a large proportion of its P205 from triple superphosphate, the water solubility is higher than in 10-10-10 even when both are ammoniated to the maximum practical degree. In the first formulation the degree of ammoniation is about as high as is practical; the water solubility is about 50 percent.
In the second formulation the degree of ammoniation has been decreased by deriving less nitrogen from ammoniating solution and more from ammonium sulfate. In order to make room in the formulation for the ammonium sulfate, it is necessary to derive a higher percentage of the PO, from triple superphosphate. The water solubility of this formulation is 75 percent; it costs about $4.20 per ton more to produce than the 50 percent solubility product. The manufacturer's profit would be about 30 percent less.
FACTORS IN PRODUCTION OF P205 FERTILIZERS
Table 4.4. Formulations and Costs for 12 -12 -12
36 T. P. HIGNETT
Comparison of tables 4.3 and 4.4 shows that a 12-12-12 of 50 percent water solubility costs about the same per unit of plant food as a 10-10-10 of 23 percent solubility.
REFERENCES CITED
1. A.O.A.C., 1955. Methods of Analysis, 8th edition, p. 10.
2. CLARK, K. G., and HOFFMAN, W. M., May, 1952. Farm Chemicals, pp. 17-23.
3. HEIN, L. B., HICKS, G. C., SILVERBERG, J., and SEATZ, L. F., 1956. Granulation of high-analysis fertilizers. Jour. Agric. Food Chem. 4:318-30.
G. L. TERMAN
Tennessee Valley Authority
Chapter 5
Crop Response to Commercial Fertilizers
Ln Relation to Granulation and
Water Solubility of the Phosphorus
EMAND for granular fertilizers in the United States and other
countries has grown in recent years. The chief reasons are the
physical advantages of granular fertilizers in regard to better storage properties and ease and uniformity of distribution for crops. Recent technological advances in granulation techniques (15) have given a marked stimulus to the production of granular fertilizers.
In addition to the physical advantages of granular fertilizers, recent investigations (10,30,46) indicate that application of nitrogen and phosphorus fertilizers together in intimate contact usually increases the availability of the phosphorus to crops, as compared to application separately. This tends to increase the efficiency of the phosphate fertilizer applied. Granulating the various components of NPK fertilizers into homogeneous granules insures very intimate contact in application for crops.
The relationships between granulation of fertilizers and water solubility of the phosphorus component will be discussed in this chapter, pointing out possible combinations which tend to increase the efficiency of fertilizer use. This, in turn, closely affects the economic return which the farmer can obtain from expenditures for fertilizer. Data from a summary of greenhouse and field experiments conducted cooperatively between TVA and seven state experiments (49) will be used extensively.
For convenience and brevity, the following abbreviations will be used:
SP - Ordinary superphosphate, 18-20 percent P201.
CSP - Concentrated superphosphate, 40-49 percent PO,.
MCP - Monocalcium phosphate, 56 percent P,05.
DCP - Dicalcium phosphate, 49 percent P205.
TCP - Tricalcium phosphate, 46 percent P205FTP - Fused tricalciurn phosphate, 28 percent P205SOLUBILITY OF VARIOUS PHOSPHORUS FERTILIZERS
Rock phosphate, which occurs largely as insoluble apatite, is the raw material from which more soluble phosphatic fertilizers are manufactured. It is also ground finely and used as a phosphorus fertilizer without further treatment. Numerous investigations have shown that crop
G. L.TERMAN
response to rock phosphate is much poorer under most soil conditions than to more soluble phosphate fertilizers. Crop response to rock phosphate will not be considered any further.
Ordinary superphosphate (SP), prepared by treating rock phosphate with sulfuric acid, contains 18 to 20 percent available P105. This material was practically the only soluble phosphorus fertilizer used for nearly 75 years after it was first made in England in 1843. The principal phosphorus compound in superphosphate is monocalcium phosphate (MCP) which is water soluble. The other major component of SP is gypsum, which supplies calcium and sulfur for plant growth.
Since about 1930, concentrated superphosphate (CSP), containing 40-49 percent available P205 and prepared by treating rock phosphate with phosphoric acid, has been increasing in supply. Its principal component is also MCP. Gypsum is absent in the product prepared with electric -furnace acid and present in only very small amounts in the product prepared with wet-process phosphoric acid. Mixtures of SP and CSP containing 30-40 percent available P205 are also sold commercially.
In recent years increasing amounts of ammonium phosphate fertilizers, in which the phosphorus is also water soluble, have been sold. The principal components of these fertilizers are monoammonium and diammonium phosphates. Water-soluble sodium and potassium phosphates are used in very small amounts as fertilizers. Liquid phosphoric acid is also used as a fertilizer, especially in irrigation water and in preparation of liquid fertilizers.
Water-insoluble phosphates which have been used commercially as fertilizers include considerable quantities of dicalcium (DCP) and tricalcium (TCP) phosphates. TVA manufactured a fused phosphate for several years, in which the phosphorus was present largely as alpha tricalcium phosphate. Rhenanian phosphate, prepared by sintering a mixture of rock phosphate, soda, and silica, is another water-insoluble phosphate material used in the areas adjacent to the western phosphate deposits. DCP is considered to be a major phosphorus component in nitric phosphate fertilizers and in ammoniated superphosphates.
Superphosphates are used as the base for preparing a large part of the NP and NPK fertilizers used in the United States. In preparing these fertilizers, the SP is usually ammoniated to varying degrees with ammonia, ammonium nitrate, or urea solutions, or mixtures of these. Extensive use of nitrogen solutions has been made since about 1928, because nitrogen in such solutions costs less than that added in solid forms of nitrogen. As a result of ammoniation, the water-soluble MCP is converted into varying amounts of water-insoluble DCP and TCP, depending on the degree of ammoniation and perhaps on the nature of other fertilizer constituents. Data of Keenen (20), White et al. (52), and others, indicate practically complete reversion of MCP to DCP an addition of about 2 percent N to SP and 6 percent N to CSP from ammoniating solutions. With further ammoniation of SP up to 6 percent N, TCP is precipitated in increasing amounts to about 30 percent of the phosphorus present. Fluorapatite may also be formed at very high degrees of
CROP RESPONSE
ammoniation. Ammoniation of CSP to about 12 percent N results in about 10 percent of the phosphorus precipitating as TCP. Ross et al.
(37) found that including ground limestone in a fertilizer to render it physiologically neutral increased the reversion of phosphorus in SP ammoniated above 3 percent N. From the above effects of ammoniation, it may be concluded that crop response to ammoniated superphosphates may be dependent in large part upon the relative contents of MCP, DCP, and TCP. These effects, from later information, are discussed by Hignett (16). With extreme ammoniation, the more insoluble hydroxyapatite may be formed.
AVAILABILITY TO CROPS OF VARIOUS CHEMICAL
FORMS OF PHOSPHORUS FERTILIZERS
Calcium Phosphates on Acid to Neutral Soils
Rogers, Pearson, and Ensminger (36) have published a comprehensive review of literature concerning calcium phosphates and other phosphate fertilizers. They conclude that DCP is as good a source of phosphorus as SP on acid to neutral soils. TCP is less effective than MCP or DCP. Liming to near neutrality or above would be expected to decrease effectiveness of TCP.
Gilbert and Pember (12) found DCP in pot tests to be about 95 percent as available as SP. Jacob and Ross (18) reported that DCP was slightly more effective, while MCP was less effective than SP in pot tests conducted by five state experiment stations and USDA. Karraker et al. (19) in pot tests from 1934-39, found the following relative yields from various phosphate sources: SP-100; CSP-94; DCP-101; TCP-77; and FTP-100.
Odland and Cox (26) found in a six-year test in Rhode Island that DCP produced slightly higher yields of hay and potatoes than SP. A later report (27) indicated no significant differences in potato yields between SP, CSP, and DCP. Houghland et al. (17) reported that DCP was nearly as effective as CSP for potatoes grown on soils ranging from pH 5.2 to 5.6 in Maine, New Jersey, and Pennsylvania.
Roberts et al. (35) found no significant differences in yields of corn, wheat, and hay, on unlimed land for SP, CSP, DCP, and TCP, although TCP was slightly less effective for corn and wheat. On limed land TCP was considerably less effective for corn and wheat than the other materials. These tests were conducted at 10 locations in Kentucky over the 1934-1940 period.
Bauer et al. (1) reported MCP, DCP, and TCP to be about equally
effective for wheat in Illinois. Rich and Lutz (34) summarized results of phosphate comparisons in Virginia through 1947. They found relative yield values for DCP as follows, as compared to 100 for CSP: wheat-94; corn-99; alfalfa-100; and mixed hay and pasture-104. Similar values for TCP were: wheat-90; corn-96; and alfalfa-98.
G. L. TERMAN
Stanford and Nelson (44) reported similar yields of oats grown on pH
6.0 Webster silty clay loam fertilized with DCP and SP, although the percentage of plant phosphorus derived from DCP was much lower than from SP. Similar uptake of phosphorus was found on two other soils on which there was no response to phosphorus fertilization. Blaser and McAuliffe
(2) reported similar forage yields from different phosphorus sources on pH 5.3 Mardin silt loam, but more of the plant phosphorus was derived from SP than from DCP or TCP. Likewise, similar yields of cotton fertilized with SP, DCP, and FTP also were reported by Hall, et al., (13). Again, much more phosphorus was taken up from SP than from DCP or FTP.
Ensminger (8) reported results from an experiment at 358 locations in Alabama over the 1934-1938 period. Relative yield increase values were: SP-100; CSP-92; DCP-99; and TCP-81. In other experiments, the relative yield increases with CSP and TCP were 90 and 87 for cotton; 106 and 109 for corn, and 89 and 89 for legumes, respectively, as compared to 100 with SP. Ensminger and Cope (9) found that yields of cotton grown on pH 6. 0 unlimed Norf olk f ine sandy loam were lowest f or MCP, intermediate for DCP, and highest for TCP. These results indicated a response to calcium in the phosphates, since there was no consistent difference in yields on limed plots. Soils on plots fertilized with TCP over a 16-year period contained more dilute acid soluble phosphorus than on those fertilized with SP, MCP, or DCP.
Seatz, Tisdale, and Winters (40) summarized results of 425 field experiments conducted from 1941 through 1953, comparing FTP and CSP. FTP was usually a satisfactory source of phosphorus on acid soils for forage crops and small grains but was less satisfactory for corn, cotton, and vegetable crops. Effectiveness of FTP, as compared to CSP, was slightly less on limed than on unlimed soils. The 10-mesh FTP was less effective than that ground more finely.
Stewart (47) has summarized much of the work in Great Britain on comparisons of various phosphate fertilizers. He concluded that DCP and various other citric acid-soluble phosphates were similar to SP in effectiveness for crops on acid soils. Cooke (5), however, reported that DCP was more efficient than SP for potatoes on soils below pH 5.5, but was inferior on less acid soils.
In summary, results cited above indicate that response to MCP in SP and CSP is equal to or slightly better than to DCP or TCP on acid soils. Liming to near-neutrality tends to decrease effectiveness of DCP and TCP, especially of the latter. Early growth response is usually greater to water-soluble than to water-insoluble phosphorus sources.
Calcium Phosphates on Alkaline Soils
Rogers, Pearson, and Ensminger (36) concluded from a review of the literature that DCP and FTP were not satisfactory sources of phosphorus on alkaline soils. Seatz, Tisdale, and Winters (40) also concluded that
CROP RESPONSE
FTP was not a satisfactory source of phosphorus on alkaline soils for any crop tested. The relative yield increase in 20 tests was only 38 percent for 40-mesh FTP, as compared to 100 for CSP.
Olsen et al. (28) found that absorption of phosphorus from DCP or FTP by various crops grown on alkaline soils in Arizona, Colorado, and Idaho was much less than from SP or phosphoric acid. Yield response to phosphorus was obtained in part of the various tests. Dion, et al., ('7), also reported that DCP was inferior to MCP on neutral to alkaline soils in Canada. Speer et al. (43) similarly reported that DCP and TCP were unsatisfactory for beans on pH 8.1 Houston black clay. Fuller (11) found that phosphorus in FTP was the least available of any source tested on alkaline soils in Arizona.
It may be concluded from the various reports cited above that DCP is less efficient, and that FTP and TCP are much less efficient, than MCP or other water-soluble sources for crops on alkaline soils.
Ammoniated Superphosphates
Parker (32) concluded from a review of the available information that the phosphorus in ammoniated SP varied in availability to crops from '75 to 100 percent of that in SP. Williamson (53) summarized results from 185 experiments conducted in Alabama from 1931-34. The following relative yield increases were obtained: SP-100; SP ammoniated to 2 percent N-100; and SP ammoniated to 4 percent N-85. Response to phosphorus was reduced much more by mixing dolomite with the SP ammoniated to 4 percent than was the case with unammoniated SP.
Salter and Barnes (39) found that the effectiveness of superphosphates ammoniated to 5 and 7 percent N decreased in pot tests with increase in soil pH from 5.5 to 7.0. The decrease was greater at the higher ammoniation. SP ammoniated below 3 percent N was 72 to 100 percent as effective as unammoniated SP over this pH range. These results agree relatively with those obtained in tests of MCP, DCP, and TCP.
Ross et al. (38) concluded that long-season crops such as wheat and Sudan grass (second cutting) can utilize phosphorus in highly ammoniated fertilizers better than short-season crops, such as millet, sorghum, and Sudan grass (first cutting).
Speer, et al., (43), reported that ammoniated SP was somewhat lower in availability than SP for beans grown on calcareous Houston black clay. The two fertilizers were equally available on pH 6.0 Susquehanna sandy loam. Martin et al. (24) also found that no effect of ammoniation of SP on availability of the phosphorus to lettuce grown on four acid soils. On two calcareous soils, however, availability was reduced by ammoniation to 4.5 percent N but not by ammoniation to 2 percent N. The unammoniated SP and that ammoniated to 2 and 4.5 percent N and 95, 67, and 30 percent, respectively, of the phosphorus in a water-soluble form.
Terman et al. (48) found little effect of ammoniation of SP to 3 or 6 percent N on yield, phosphorus content, or percentage of the phosphorus
G. L. TERMAN
from the fertilizer for potatoes grown on unlimed and limed Caribou loam. In similar experiments in North Carolina and Virginia (33), no differences were found in yield of corn and tobacco or in the percentage of the plants' phosphorus derived from the fertilizer. Results in Mississippi (33) indicated a tendency for lower yields of seed cotton on a neutral soil with increasing degrees of ammoniation. Ammoniation to 6 percent N decreased the percentage of the plants' phosphorus derived from the fertilizer. Ammoniation to 2, 3, or 4 percent N had no effect.
It may be concluded from the above research that ammoniated superphosphates are increasingly less efficient than the unammoniated materials on calcareous soils with increase in reversion of MCP to DCP and TCP. On acid soils, this tendency is less, although liming to neutrality or above often reduces efficiency of the phosphorus in ammoniated fertilizers. Yields of short-season crops and early growth of long-season crops are usually reduced by ammoniation, especially on soils in the higher pH ranges.
Ammonium Phosphates
Monoammonium phosphates are usually produced commercially alone as a 11-48-0 fertilizer or together with ammonium phosphate -sulfate as 16-20-0. Diammonium phosphate is produced by TVA and a few fertilizer producers as a 21-53-0 material. The phosphorus in all of these fertilizers is entirely water -soluble.
Maclntire et al. (23) found no difference in crop response on acid soils to CSP and monoammonium or diammonium phosphates.
Olson et al. (29, 30) found higher crop response to CSP plus nitrogen and ammonium phosphates than to most other phosphorus materials on Nebraska soils. In these experiments placing the nitrogen and phosphorus together increased availability of the phosphorus.
A summary of crop yields in 82 experiments as shown in table 5.1, indicates that the phosphorus in diammonium phosphate and CSP is of similar availability.
Phosphoric Acid
Thorne (50) found no differences in yields of potatoes, wheat, or sugar beets fertilized with CSP and H3,P04. Fuller (11) obtained results showing somewhat more of the plant phosphorus in alfalfa and cotton grown on calcareous soils in Arizona was taken from H3P04 than from SP. Yield response to phosphorus was not obtained in most tests. Olsen, et al.,
(28), also found similar yields and percentages of the plant phosphorus in alfalfa grown on calcareous soils in Colorado with SP and H' P04. H3PO4 supplied appreciably more of the plant phosphorus than CSP from a late application for sugar beets. Hausenbuiller and Weaver (14) reported that H3P04 produced slightly higher yields of alfalfa on calcareous
CROP RESPONSE
Sagemoor fine sandy loam than CSP. Amounts of phosphorus taken up by the crop were also higher. Converse (4), however, found that alfalfa yielded considerably less with HP04 than with SP or CSP. He concluded that more leaching of phosphorus from H3P04 by irrigation water had occurred on the calcareous, Superstition fine sand overlaying coarse sands.
Table 5.1. Crop Response to TVA Diammonium Phosphate Fertilizers, 1950-55a
States Reporting Number Relative Response
Crop Field Test Results of Tests (CSP =100)
Corn Ga., Iowa, Ky., Miss., Tenn. 27 99
Cotton Ala., Miss., Tenn. 6 98
Legume hay Tenn., Va., Wash. 7 94
Small grains Ala., Colo., Ga., Iowa, Ky.,
N.C., N.Y., Tenn., Va. 26 101
Vegetables Colo., Wash. 16 102
All crops All states 82 100
aData. taken from annual reports to TVA of cooperative fertilizer evaluation experiments.
Less work with H-LP04 has been done on acid soils. Maclntire et al.
(22) reported slightly lower contents and uptake of phosphorus by rye grass grown in pot tests on pH 5.2 Fullerton silt loam from various dilutions of H3PO4 than from CSP. Similar results were obtained with red clover grown on this soil limed to pH 7.2.
Results of research indicate in general that effectiveness of phosphorus in H3P04 for crop growth is similar to that in SP or CSP.
WATER SOLUBILITY AND GRANULE SIZE RELATIONSHIPS
WITH SUPERPHOSPHATES AND NPK FERTILIZERS
Effects of granulation on the efficiency of fertilizers are largely in relation to the availability of the phosphorus component. Most nitrogen and potassium compounds are readily water-soluble and move rapidly into the soil from fertilizer, in either granular or powdered forms. Mehring et al. (25), for example, found that a large part of the phosphorus applied in granular fertilizers for cotton remained in the fertilizer zone, while nitrogen and potassium had disappeared. Subsequent discussion will be in regard to water solubility and granule size relationships with the phosphorus component of fertilizers.
Lawton and Vomocil (21) found that at field moisture capacity, 50-80 percent of the water-soluble phosphorus moved out of granules of superphosphate in 24 hours. Twenty to 50 percent moved out in this period from soils containing as low as 2-4 percent moisture. The movement of
G. L. TERMAN
water-soluble phosphorus out of NPK fertilizer granules into a sandy loam soil was found by Owens et al. (31) to be essentially complete in 48 hours. The extent of movement from large granules and the concentration of phosphorus in the soil around the granules were directly related to the percentage of water-soluble phosphorus in the fertilizer. Skinner et al. (42) observed that about 50 percent of the available P205 remained in granules of 6-7.5-6 fertilizer applied for cotton.
Table 5.2. Fertilizers Used in the Granule Size and Water Solubility Experiments (47)
Granule Available Water-Soluble Fertilizer Grade Size-Meshes P205, % P205, % Of and Abbreviation' per Inch of Total Available Formulationsa
7-14-14 -6+14 99 7 Mixture of
(DCP) -14+35 99 8 DCP, AS,
-35 99 5 and KC I
6-12-12 -6+14 96 27 Ammoniated
(AOSP) -14+35 96 2,5 OSP, AN,
-35 96 28 and KCl
10-20-20 -6+14 94 60 Ammoniated
(ACSP) -14+35 94 60 CSP, AN, AS,
-35 93 61 and KCl
11-22-22 -6+14 100 100 Mixture of
(DAP) -14+35 100 99 DAP, AS,
-35 100 100 and KClI
aDCP - dicalcium phosphate; OSP - 18 to 20 superphosphate; CSP - concentrated superphosphate; DAP - diammonium phosphate; AN - ammonium nitrate; AS - ammonium sulfate; and KCl - muriate of potash.
Results of studies of crop response to granular and pulverized fertilizers have been inconclusive, as pointed out by Sherman and Hardesty
(41) and Starostka et al. (45). Most of the results indicated that for fertilizers broadcast and mixed with the soil, differences in granule size had no measurable effect on crop response, or else granules 10-mesh or larger, or briquettes, produced the highest yields. Presumably, the large granules or briquettes were most effective on soils of high phosphorusfixing capacity. In the case of localized hill or band placements of fertilizers, occasional decreases in yield have been reported for granulated, as compared to pulverized fertilizers. Terman et al. (48), for example, found that granular superphosphate produced lower yields of potatoes than pulverized material when both were applied in row side bands.
Starostka et al. (45) reported that 14-20 mesh granules of superphosphate and 28-35 and -35 mesh granules of dicalcium phosphate resulted in best response by wheat grown in greenhouse pots. Bouldin (3) compared 8-10, 12-14, 16-20, and 28-32 mesh granules of a water-soluble phosphate for oats on six Iowa soils. He found that the phosphorus in the
CROP RESPONSE
larger granules was most available in five acid to neutral soils but that the reverse was true for the calcareous Ida silt loam. Owens et al. (31) found that absorption of phosphorus from fertilizer by wheat increased markedly with increase in soluble phosphorus in 4-6 mesh granules, but was affected very little in the case of pulverized fertilizer. Webb (51) found that the effectiveness of fertilizers applied with or near the seed for corn and oats increased with increase in water solubility of the phosphorus. This relationship was more pronounced on alkaline than acid Iowa soils, and much less for broadcast than for localized applications.
Terman et al. (49) reported crop responses in 21-field and 2-greenhouse pot experiments to NPK fertilizers having percentages of watersoluble phosphorus of 7, 27, 60, and 100. Each fertilizer was granulated into three mesh sizes: 6-14, 14-35, and -35. The fertilizers were prepared in 1-2-2 ratio from DCP, ammoniated SP, CSP, and diammonium phosphate, respectively. Characteristics of these fertilizers are summarized in table 5.2.
Crop Response in Greenhouse Experiments
There was a marked interaction between granule size and level of
water-soluble phosphorus in the fertilizers compared in greenhouse experiments (47), especially for the first crop. These relationships are shown in figure 5.1. Yields increased markedly with decrease in granule size of the low water-soluble 7-14-14 DCP mixture and to a lesser extent for the 27 percent water-soluble 6-12-12 ammoniated SP. A marked reverse relationship was found for the 100 percent water-soluble 11-22-22 diammonium phosphate mixture and to a lesser extent for the 60 percent water-soluble 10-20-20 ammoniated CSP. Very similar relationships were found for uptake of phosphorus by the crops. This interaction of water solubility and granule size was highly significant for 4 of the 5 soils on which the comparisons were made. Crop response to the 35-mesh DCP and to the 6-14 mesh diammonium phosphate fertilizers was of similar magnitude. A lower mean response to ammoniated SP than to DCP was obtained for the first crop, although the former has the higher water solubility of phosphorus. Reasons for this are not evident. Lower availability of the water-insoluble phosphorus fraction of the ammoniated SP than DCP might be a cause, although petrographic observations do not support this explanation. It was observed that the granules of the ammoniated SP were much harder than those of DCP and slaked much more slowly in water. The effects of such physical characteristics on availability of fertilizers to plants have not been adequately determined. The presence of gypsum in the ammoniated SP may also result in reduced solubility of DCP, as found by Starostka and Hill (46). They did not, however, find the application of gypsum with DCP to decrease the availability of its phosphorus significantly to crop plants.
In the second crop the yield of dry matter and uptake of phosphorus again increased with decrease in granule size of the 7 and 27 percent
G. L.TERMAN
water-soluble materials, but to a lesser extent than for the first crop. For the 60 and 100 percent water-soluble fertilizers there was no appreciable effect of granule size on second crop response or uptake of phosphorus.
RELATIVE YIELD
Fig. 5.1 - Effect of granule size and percent water-soluble P on mean relative yields of two greenhouse crops of Sudangrass and oats. (Mean yield of each crop from all phosphate fertilizers in 2 Tennessee and 3 Virginia soils =100.)
Presumably, the marked influence of granule size on phosphorus
availability in the lower water- soluble fertilizers is largely an eff ect on rate of solubility. The opposite influence of granule size in the case of the more highly water-soluble fertilizers is apparently related to greater fixation of phosphorus into difficultly available forms when smaller granules are applied. As evidenced by first crop response, it appears that in the range of water solubility of phosphorus between 27 and 60 percent, the tendencies for dissolution of phosphorus in the granules and fixation by the soil tended to balance each other in the soils used in these experiments. At some level in this range, granule size evidently would have little effect on airailability of the phosphorus for crop growth. This level would be expected to vary among soils differing in phosphorus-fixing capacity and other characteristics influencing soil-phosphorus reactions. This observation may account for some of the inconclusive results with granulated and nongranulated superphosphates, as reviewed by Sherman and Hardesty
(41), and others.
CROP RESPONSE
RELATIVE YIELD
1 0118 119
112
102 102
l00o 98
96
90-89
87
84 8
80 - 1 1 1_ 84__ _ _6-14 14-35-35 6-14 14-35 -35 I6-14 14-35 -35 6-14 14-35-35
7% 27% 60% 100%
(7-14-14) (6-12-12) (10-20-20) (1-22-22)
Fig. 5.2 - Effect of granule size and percent water-soluble P on mean relative yields of wheat forage in Mississippi. (Mean yield from all phosphate fertilizers in 4 field experiments =100.)
It would appear that by the time of growth of the second crop,- much ol the phosphorus in all granule sizes had undergone dissolution and fixation, so that original granule size had much less eff ect on second crop response.
Crop Response in Field Experiments
Wheat for Forage- -Results of winter wheat forage experiments in Mississippi (47), summarized in figure 5.2, show about the same relationships between granule size and water solubility of the phosphorus as do the data from the first crop in the greenhouse experiments shown in figure 5. 1. The interaction between granule size and water solubility was also significant at the 5 percent level in one of the four experiments This agreement might be expected, since the crops in both sets of experiments were harvested at a comparable stage of growth prior to heading. The relative yield differences among granule sizes were less in the field than in the greenhouse, especially with 6-12-12 ammoniated SP. One fac: tor may be that more soil phosphorus was utilized in the field than in the greenhouse, so that the applied fertilizer had relatively less effect. In
G. L. TERMAN
the field, all granule sizes of diammonium phosphate (11-22-22) resulted in greater yields than the other fertilizers of lower water solubility. These results obtained in the field are essentially in agreement with those reported on wheat grown in the greenhouse by Starostka et al. (43).
Wheat for Grain--There was much less difference in yield of wheat grain for the various fertilizers than for wheat forage shown in figure 5.2. No differences in yield of grain were statistically significant in a winter wheat experiment in Georgia on Fannin loam and in the North Carolina and Tennessee experiments, in which early growth yields were not taken. In a Georgia experiment on Altavista loam, the 14-35 mesh granules yielded significantly more wheat (5 percent level) than the other granule sizes. Apparently, with the longer growth period necessary for harvest of grain from winter wheat, a high content of water-soluble phosphorus in the fertilizer is of much less importance than for early growth. Similar observations were made by DeMent and Seatz (6) and Olson et al. (29).
In a Washington experiment with spring wheat forage, both in field and greenhouse, response to the 6-12-12 fertilizer was significantly poorer (1 percent level) than to the other fertilizers. The interaction between water solubility and granule size was also significant (5 percent level) for wheat forage in the greenhouse and one field experiment. Similar differences were found in yield and phosphorus content for wheat forage harvested both in early joint stage of growth and in final grain yields. The interaction between water solubility and granule size was significant for both the early forage yields and phosphorus content.
Corn and Cotton--Only in the case of the low water-soluble 7-14-14 fertilizer, as shown in figure 5.3, was there an appreciable difference in mean yield response of corn and cotton resulting from difference in granule size. Mean yields for the seven experiments conducted also showed practically no difference among the fertilizers of different water solubility. There were no significant differences in any experiment for granule size, water solubility, or interaction, except for a Georgia experiment on Altavista loam, in which the 14-35 mesh granule size yielded significantly higher (5 percent level) than the other mesh sizes.
Early growth response was closely related to water solubility of the phosphorus in all of the experiments. In one Kentucky experiment in 1955, there was a highly significant increase in height of corn four weeks after planting with increase in water solubility. Early growth differences, however, did not carry through the relatively long growing season on these southern soils or have an appreciable effect on yield of corn grain or seed cotton. Similar effects on corn were observed by DeMent and Seatz (6). Content of phosphorus in the leaves when the corn was two to four feet and the cotton was eight inches high, on Sequoia and Mountview soils in Tennessee, was likewise not significantly affected by differences in the fertilizer. Owens et al. (31), on the other hand, found that phosphorus content of sugar beet plants fertilized with a highly water-soluble phosphate was significantly higher than for plants fertilized with one of lower water solubility. No differences, however, were found in final yields of beets.
CROP RESPONSE
RELATIVE YIELD
6-14 14-35-35 1 6-14 14-35-35 16-14 14-35-35 1 6-14 14-35-35 1
7% 27% 60% 100%
(7-14-14) (6-12--12) (10-20-20) (I I222
Fig. 5.3 - Effect of granule size and percent water-soluble P on mean relative yields of corn grain and seed cotton in Georgia, Kentucky, and Tennessee.
(Mean yield from all phosphate fertilizers in 6 corn and 1 cotton experiments = 100.)
Vegetable Crops--As shown in figure 5.4, there was a pronounced increase in yield of vegetable crops in Washington with decrease in granule size of the 7-14-14 and 6-12-12 fertilizers. Differences for the fertilizers higher in water solubility were not appreciable. Mean response to DCP was significantly poorer (5 or 1 percent levels) than to the other fertilizers in all experiments except with potatoes. The interaction between granule size and water solubility was significant in the experiment with potatoes and one with sweet corn. Phosphorus content of potato leaves sampled 45 days after planting was significantly higher with diammoniumn phosphate than with fertilizers of lower solubility. This effect did not, however, influence final potato yields appreciably.
CONCLUSIONS
Water-insoluble sources of phosphorus such as DCP and TCP are less available to crops on alkaline soils than water-soluble sources and generally should not be recommended for use on these soils. DCP has been found to give satisfactory yields on some alkaline soils, however, if applied as a finely divided material and mixed well with the soil. On acid
G. L. TERMAN
to neutral soils availability of the phosphorus in water-insoluble materials tends to be a function of solubility and increases with decrease in particle size. Granulation of water-insoluble materials in granules larger than about 35 mesh usually lowers availability of the phosphorus to crops.
i- RELATIVE YIELD
Fig. 5.4 - Effect of granule size and percent water-soluble P on mean relative yields of vegetable crops in Washington. (Mean yield from all phosphate fertilizers in 5 experiments = 100.)
For highly water-soluble phosphorus fertilizers, the forces of solution and movement of phosphorus from the fertilizer granule or band tend to interact with the tendency for fixation by the soil in determining the availability of phosphorus to plants. The results of several investigators indicate that the movement of water-soluble phosphorus from fertilizer granules or bands is essentially complete in a few days after application to the soil. This phosphorus moves out into a relatively small sphere surrounding the granule or point of application of pulverized fertilizer leaving behind a residue which, in the case of superphosphate, may contain as much as 50 percent of the total phosphorus content. Once the initial movement of phosphorus is completed, it is made relatively immobile by fixation in the soil, in contrast to nitrogen which moves about freely in the soil with movement of water.
Phosphorus applied for a crop at time of planting is thus largely
CROP RESPONSE
immobilized by the time of emergence of the plants and remains so throughout the growth period. Concentration of phosphorus near the emerging plant is quite important and tends to govern the early growth response to phosphorus.
Because of the variable tendencies for movement and fixation, the best combination of percentage water solubility and granule size may differ markedly for different soils. In general, the greater the phosphorus-fixing capacity of a soil, the larger should be the granule size of a highly water-soluble fertilizer. Banding of pulverized water-soluble materials near the seed appears to be a satisfactory substitute for granulation in many soils. In alkaline soils, where fixation of phosphorus into difficultly soluble forms is less important than in acid soils, application of pulverized fertilizers mixed with the soil may be more satisfactory than application of granular fertilizers mixed with the soil, or of pulverized fertilizers in bands.
Considerable research *must be done to determine more exactly the relationships among water solubility, granule size, placement and various soil characteristics in relation to plant availability of phosphorus. The nature of the fertilizer salts with which the phosphorus is associated is also of considerable importance in determining its availability to plants.
REFERENCES CITED
1. BAUER, F. C., LANG, A. L., BADGER, C. T., MILLER, L. B., FARNHAM, C.
H., JOHNSON, P. E., MARRIOTT, L. F., and NELSON, M. H., 1945. Effects
of soil treatment on soil productivity. Ill. Agr. Exp. Sta. Bul. 516.
2. BLASER, R. E., and McAULIFFE, C., 1949. Utilization of phosphorus from various fertilizer materials: I. orchard grass, and ladino clover in New York.
Soil Sci. 68:145-50.
3. BOULDIN, D. R., 1956. Particle size effects of soluble phosphate fertilizers.
Ph.D. Thesis, Iowa State College.
4. CONVERSE, C. D., 1948. Phosphorus fertility and movement studies on newly reclaimed sandy soils. Proc. Soil Sci. Soc. Amer. 13:423-27.
5. COOKE, G. W., 1956. Alternatives to superphosphates. Jour. Ministry of Agr. 62:27-30.
6. DEMENT, J. D., and SAETZ, L. F., 1956. Crop response to high-alumina nitric phosphate fertilizers. Jour. Agr. Food Chem. 4:432-35.
7. DION, H. G., DEUM, J. E., and SPINKS, J. W., 1949. Study of fertilizer uptake using radioactive phosphorus. Sci. Agr. 29:512-26.
8. ENSMINGER, L. E., 1950. Response of crops to various phosphate fertilizers.
Ala. Agr. Exp. Sta. Bul. 270:1-39.
9. - , and COPE, J. T., Jr., 1947. Effect of soil reaction on the efficiency of various phosphates for cotton and loss of phosphorus by erosion. Jour.
Amer. Soc. Agron. 39:1-li.
G. L. TERMAN
10. FINE, L. 0., 1955. The influence of nitrogen and potassium on the availability
of fertilizer phosphorus. S. D. Agr. Exp. Sta. Bul. 453:1-22.
11. FULLER, W. H., 1953. Effect of kind of phosphate fertilizer and method of
placement on phosphorus absorption by crops grown in Arizona calcareous
soil. Ariz. Agr. Exp. Sta. Tech. Bul. 128:231-55.
12. GILBERT, B. E., and PEMBER, F. R., 1936. A study of the availability of
ammoniated superphosphate and various unusual phosphate carriers by means
of vegetative pot tests. R. I. Agr. Exp. Sta. Bul. 256.
13. HALL, N. S., NELSON, W. L., KRANTZ, B. A., WELCH, C. D., and DEAN, L.
A., 1949. Utilization of phosphorus from various fertilizer materials: II. Cotton and corn in North Carolina. Soil Sci. 68:151-56.
14. HAUSENBUILLER, R. L., and WEAVER, W. H., 1954. A comparison of phosphate fertilizers for alfalfa on irrigated Central Washington soils. Wash. Agr.
Exp. Sta. Cir. 257.
15. HEIN, L. B., HICKS, G. C., SILVERBERG, J., and SEATZ, L. F., 1956. Granulation of high-analysis fertilizers. Jour. Agr. Food Chem. 4:318-30.
16. HIGNETT, T. P., 1956. Technical and economic factors involved in production of fertilizers of high water soluble P205 content by conventional processes.
Com. Fert. 92:(5)23-24, 26, 67.
17. HOUGHLAND, G. V., CLARK, K. G., HAWKINS, A., and CAMPBELL, J. C.,
1942. Nutrient value of some new phosphatic materials used on potatoes.
Amer. Fert. 97(7):5-8,24,26.
18. JACOB, K. D., and ROSS, W. H., 1940. Nutrient value of the phosphorus in
defluorinated phosphate, calcium metaphosphate, and other phosphatic materials as determined by growth of plants in pot experiments. Jour. Agr. Res.
61:539-60.
19. KARRAKER, P. E., MILLER, H. F., BORTNER, C. E., and TODD, J. R., 1941.
Greenhouse tests of the availability of phosphorus in certain phosphate fertilizers. Ky. Agr. Exp. Sta. Bul. 413:57-86.
20. KEENEN, F. G., 1930. Reactions occurring during the ammoniation of superphosphate. Ind. Eng. Chem. 22:1378-87.
21. LAWTON, K', and VOMOCIL, J. A., 1954. Dissolution and migration of phosphorus from granular superphosphate in some Michigan soils. Proc. Soil Sci.
Soc. Amer. 18:26-32.
22. MACINTIRE, W. H., WINTERBERG, S. H., CLEMENTS, L. B., and JOHNSON,
H. W., Jr., 1947. The effectiveness of liquid orthophosphoric acid. Jour.
Amer. Soc. Agron. 39:971-80.
23. -, and STERGES, A. J., 1950. Fertilizer evaluation of monoammonium
and diammonium phosphates by means of pot cultures. Agron. Jour. 42:442-46. 24. MARTIN, W. E., VLAMIS, J., and QUICK, J., 1953. Effect of ammoniation on
availability of phosphorus in superphosphate as indicated by plant response.
Soil Sci. 75:41-49.
25. MEHRING, A. L., WHITE, L. M., ROSS, W. H., and ADAMS, J. E., 1935. Effects of particle size on the properties and efficiency of fertilizers. USDA,
Tech. Bul. 485.
26. ODLAND, T. E., and COX, T. R., 1942. Field experiments with phosphate
fertilizer. R. I. Agr. Exp. Sta. Bul. 281.
CROP RESPONSE
27. - , BELL, R. S., and SCHALLOCK, D. A., 1951. Potato growing in Rhode
Island. R. I. Agr. Exp. Sta. Bul. 310.
28. OLSEN, S. R., SCHMEHL, W. R., WATANABE, F. S., SCOTT, C. 0., FULLER,
W. H., JORDAN, 3. V., and KUNKEL, R., 1950. Utilization of phosphorus by
various crops as affected by source of material and placement. Colo. Agr.
Exp. Sta. Tech. Bul. 42:1-43.
29. OLSON, R. A., DREIER, A. F., LOWREY, G. W., and FLOWERDAY, A. D.,
1956. Availability of phosphate carriers to small grains and subsequent clover in relation to: I. Nature of soil and method of placement. Agron. Jour. 48:10611.
30. , , , and - , 1956. Availability of phosphate carriers
to small grains and subsequent clover in relation to: II. Concurrent soil
amendments. Agron. Jour. 48:111-16.
31. OWENS, L., LAWTON, K., ROBERTSON, L. S., and APOSTOLAKIS, C., 1955.
Laboratory, greenhouse, and field studies with mixed fertilizers varying in
water soluble phosphorus content and particle size. Proc. Soil Sci. Soc. Amer.
19:315-19.
32. PARKER, F. W., 1931. The availability of phosphoric acid in precipitated
phosphates. Com. Fert. 42:(5)28-44.
33. PEARSON, R. W., 1951. Summary of cooperative radiophosphorus field experiments, 1950. Div. Soil Management and Irrigation, USDA.
34. RICH, C. I., and LUTZ, J. A., Jr., 1950. Crop response to phosphate fertilizers in Virginia. Va. Agr. Exp. Sta. Tech. Bul. 115:1-14.
35. ROBERTS, G., FREEMAN, J. F., and MILLER, J., 1942. Field tests of the
relative effectiveness of different phosphate fertilizers. Ky. Agr. Exp. Sta.
Bul. 420:1-31.
36. ROGERS, H. T., PEARSON, R. W., and ENSMINGER, L. E., 1953. Comparative efficiency of various phosphate fertilizers. Agronomy 4:189-242. Academic Press, Inc., New York.
37. ROSS, W. H., RADER, L. F., Jr., and BEESON, K. C., 1938. Citrate-insoluble
phosphoric acid in ammoniated mixtures containing dolomite, Jour. Assoc.
Offic. Agr. Chem. 21:258-68.
38. - , ADAMS, 3. R., HARDESTY, J. 0., and WHITTAKER, C., 1947. Factors affecting the availability of ammoniated superphosphates as indicated by
pot tests in the greenhouse. Jour. Offic. Agr. Chem. 30:624-40.
39. SALTER, R. M., and BARNES, E. E., 1935. The efficiency of soil and fertilizer phosphorus as affected by soil reaction. Ohio Agr. Exp. Sta. Bul. 553:149.
40. SEATZ, L. F., TISDALE, S. L., and WINTERS, E., 1954. Crop response to
fused tricalcium phosphate. Agron. Jour. 46:574-80.
41. SHERMAN, M. S., and HARDESTY, J. 0., 1950. Plant Food Memo. Report
No. 20. Div. Fert. and Agr. Lime, USDA.
42. SKINNER, J. J., MCKAIS, N., Jr., HARDESTY, 3. 0., COLLINS, E. R.,
KILLINGER, G. B., and STACY, S. V., 1941. Effectiveness on cotton soils of
granulated mixed fertilizers of different particle size. Jour. Amer. Soc.
Agron. 33:314-24.
43. SPEER, R. I., ALLEN, S. E., MALONEY, M., and ROBERTS, A., 1951. Phosphate fertilizers for the Texas blacklands. Soil Sci. 72:459-64.
G. L. TERMAN
44. STANFORD, G., and NELSON, L. B., 1949. Utilization of phosphorus from
various fertilizer materials: III. Oats and alfalfa in Iowa. Soil Sci. 68:157-61. 45. STAROSTKA, R. W., CARO, T. H., and HILL, W. L., 1954. Availability of
phosphorus in granulated fertilizers. Proc. Soil Sci. Soc. Amer. 18:67-71.
46. - , and HILL, W. L., 1955. Influence of soluble salts on the solubility and
plant response to dicalcium phosphate. Proc. Soil Sd. Soc. Amer. 19:193-98. 47. STEWART, A. B., 1953. Factors influencing phosphate usage in Great Britain.
Agronomy 4:427-48. Academic Press, Inc., New York.
48. TERMAN, G. L., HAWKINS, A., CUNNINGHAM, C. E., and CARPENTER, P.
N., 1952. Rate, placement and source of phosphorus fertilizers for potatoes
in Maine. Me. Agr. Exp. Sta. Bul. 506:1-24.
49. - ,,A NTHONY, J. L., MORTENSEN, W. P., and LUTZ, 3. A., Jr., 1956.
Crop response to NPK fertilizers varying in granule size and water solubility
of the phosphorus. Proc. Soil Sci. Soc. Amer. 20:551-56.
50. THORNE, D. W.2 1944. The use of acidifying materials on calcareous soils.
lour. Amer. Soc. Agron. 36:815-28.
51. WEBB, 3. R., 1955. Significance of water solubility in phosphate fertilizers.
Ag. Chem. 10:(3)44-46.
52. WHITE, L. M., HARDESTY, J. 0., and ROSS, W. H., 1935. Ammonlation of
double superphosphate. Ind. Eng. Chem. 27:562-67.
53. WILLIAMSON, J. T., 1935. Efficiency of ammoniated superphosphate for
cotton. Jour. Amer. Soc. Agron. 27 :724-28.
PART 11
An Examination o/ Liquid Fertilizers and Related Marketing Problems
0, Economics of Manufacture
Economics of Farm Use
Potential Markets
Response Effects
L. S. ROBERTSON, J. F. DAVIS, and C. M. HANSEN Michigan Agricultural Experiment Station
Chapter 6
Factors Affecting the Evaluation
of Liquid Fertilizers
LIQUID fertilizer is defined as any liquid containing one or more
available plant nutrients. Such materials containing a single plant food or a mixture of two or more plant foods are on the
market in many states. At the present time there is considerable interest in this new form of fertilizer because an intensive advertising campaign is in effect and because liquid fertilizers offer certain advantages over the solid forms. Since the widespread use of liquid fertilizer is relatively new, it is natural that its advantages are stressed by producers and distributors. However, certain disadvantages in utilization do exist and should be included in an evaluation of liquid fertilizers.
The interest of the research personnel of the Michigan Agricultural Experiment Station was greatly stimulated when the price of the liquid fertilizer became competitive with the conventional dry forms. In 1955, research was initiated to determine the value of liquid as compared to dry fertilizers. The advantages and disadvantages of liquid fertilizers over conventional dry fertilizers as determined by experience with these new materials are listed below. With increased use and interest in liquid fertilizers, some of the problems now present, undoubtedly, will be solved in the future. The remarks with regard to liquid fertilizers will refer only to those without free ammonia pressure.
ADVANTAGES OF LIQUID OVER CONVENTIONAL DRY FERTILIZERS
1. Liquid fertilizers can be handled with small pumps with a saving of labor.
2. Uniform broadcast application is easily obtained by spraying.
3. Materials are completely soluble in water so they can be used in
irrigation water and as starter solutions.
4. Uniform mixtures of plant.nutrients result from their use.
5. Pesticides are compatible with many liquid fertilizers. Simultaneous application saves time and insures uniform application.
6. The use of liquids simplify ies custom mixing of fertilizer grades.
7. Liquids may be used as foliar sprays.
8. The availability of nitrogen and potassium is not decreased when
applied to the soil in liquid form.
L. S. ROBERTSON, J. F. DAVIS, C. M. HANSEN
DISADVANTAGES OF LIQUID OVER CONVENTIONAL DRY FERTILIZERS
1. Special equipment is required.
2. Special storage containers are necessary.
3. Complete fertilizers in liquid form can be made only in relatively low grades and they contain very small quantities of secondary or
minor elements.
4. Application equipment for placing fertilizer in recommended position with respect to the seed in the soil is generally unavailable.
5. Phosphorus fixation (a decrease in solubility or availability) in the soil may be increased.
6. Calcium and magnesium contents of liquid fertilizers have to be kept low to prevent precipitation of other plant nutrients.
7. Rates of actual nutrients applied may be limited because of the large volume of water needed.
8. Liquid fertilizers corrode certain metals.
9. Liquid fertilizers may be more difficult to merchandise. 10. Completely soluble carriers are required for the manufacture of
solutions; setting a limitation on carriers which may be used.
11. Grades high in potassium, suitable for several crops growing on
light sandy or organic soils, are difficult to formulate unless low
grade fertilizers are accepted.
EFFECT ON CROP YIELDS
In summarizing the 1955 results, it is realized that data obtained in one year are not sufficient to completely evaluate the new form of fertilizer. A summary of results is included because in several instances a significant difference in yield caused by liquid and solid forms was obtained. Also, the summary is included because only a limited amount of such information is available.
. In one trial on wheat, the two forms of complete fertilizer had equal effects on yield. In three trials on oats, similar results were obtained.
Corn grown in four trials showed phosphorus deficiency symptoms to various degrees of intensity in the early part of the season. The yields from these trials are shown in table 6.1. At one location, the liquid fertilizer plots yielded 20 bushels less corn per acre than did the dry fertilizer plots. At another location, in a fertilizer rate and placement experiment, corn yields were 17 bushels lower where N, P,05 and KO, each at 50 pounds per acre, were sprayed on the surface of the soil than where they were injected in liquid form into the soil near the row before the first cultivation. Higher rates of the same fertilizer (100 pounds of N, P205 and K20 per acre) sprayed on the surface of the soil were as effective as solid fertilizer and as'effective as the lower rate of liquid fertilizer injected into the soil.
In trials on organic soils, liquid fertilizer resulted in lower yields
EVALUATION OF LIQUID FERTILIZERS Table 6.1. The Effect of Liquid and Solid Fertilizers on
Corn Yields in 1955
Pounds per Acre Yield Bushel per
Soil Type N + P205 + K20 Liquid Acre Solid
Kalamazoo sandy loam 20+40+20 4.b39.4c
40+80+40 49.0b 44.6c
80+160+80 49.0b49c
160+320+160 49.0b 490Oc
320+640+320 46.4b 44.7c
Conover silt loam 10+40+40 63.0& 62.7d
Conover loam 10+40+40 74.0b 94.0d
Kalamazoo sandy loam 50+50+50 injected 72.9
50+50+50 sprayed 56.0
100+100+100 injected 73.7
100+100+100 sprayed 73.6
100+100+100 75.7e
aTopdresse 'd after the crop was planted. blnjected into the soil near the row before the first cultivation. 'Broadcast and plowed down before planting. dFertilizer applied at planting time in bands below and to the side of the seed. eoadcast at same time as liquid was sprayed on surface. of onions, carrots, and table beets than were obtained with solid fertilizers (table 6.2). In each of these experiments, the fertilizer was applied with a specially designed applicator in a band 2 inches below the seed thus eliminating any effect from differential placement. Where 800 pounds of 5-10-10 was applied, the onions with liquid fertilizer yielded 151, 50-pound bags per acre less than did those grown with solid fertilizer. Based on harvest time prices, this difference amounted to $300 an acre.
SPECIAL USES FOR LIQUID FERTILIZER
Inquiries are sometimes made in regard to treating seed with liquid fertilizer. Tests made in several states have shown that there is little or no value obtained in early growth characteristics or yield from treating seed with liquid fertilizer.
Liudfertilizers are of value as starter solutions for transplanted veetable crops, especially if the transplants are large in size. Liquids containing the major plant food elements nitrogen, phosphorus, and potassium are sometimes used for leaf feeding. Under some conditions this has proven to be a desirable practice. For field crops, this practice usually is not recommended because only a small amount can be applied without injury to foliage. Foliar applications of secondary and minor elements such as manganese, magnesium, copper, zinc, or boron are more satisfactory because small quantities are
L. S. ROBERTSON, J. F. DAVIS, C. M. HANSEN
required. In Michigan, 1.2 pounds of manganese sprayed on leaves of sugar beets and beans have given as good results as 24.0 pounds broadcast on the surface of the soil.
Table 6.2. The Effect of Liquid and Solid Fertilizers on Yields of Onions,
Table Beets, and Carrots Grown on Houghton Muck in 1955
Treatment Onionsb
Lbs. 5-10-10 50 Lb. Bags Tons per Acre
per Acre per Acre Table Beetsc Carrotsd
Expt. No. la 800 dry 925 20.6 39.4
800 liquid 774 18.3 38.7
400 dry 712 18.4 38.5
400 liquid 691 17.4 38.9
No fertilizer 254 11.8 36.6
Expt. No. 2a 800 dry 861 25.2 31.2
400 dry 837 26.8 32.0
2400 liquid 769 - 27.5
1200 liquid 838 27.0 30.9
No fertilizer 505 14.9 29.6
aExperiment No. 1 planted 5/6/55; mental Farm. bDownings Y.G. Onions. CDetroit Dark Red Beets. dChantenay Carrots.
Experiment No. 2 planted 5/5/55 Muck Experi-
Z. A. STANFIELD
Tennessee Valley Authority
Chapter 7
Economics of Manufacture of
Liquid Mixed Fertilizers'
HE manufacture and use of liquid fertilizers containing two or
more of the major plant nutrients have received considerable attention during the past few years. Several papers have been published on this subject (2, 3, 4). Most of the activity in this business has occurred in California and some has occurred in the Midwest and Southwest.
Although significant,. the estimated quantity of liquid mixed fertilizers used in the United States has been very small in comparison with the total estimated quantity of mixed fertilizers. For example, one estimate (4) showed that the quantity of liquid mixed fertilizers used during 1953-54 was 27,548 tons, or less than 0.2 percent of the total amount of mixed fertilizers used.
The present growth of the business began with the introduction on the market of "phosphatic fertilizer solution" at a price low enough to compete in some areas on the fertilizer materials market. In addition to use in making liquid mixed fertilizers, this phosphoric acid solution is used in making solid nitric phosphate and solid diammonium phosphate fertilizers. The material usually is sold as 75 percent H3PO4 It is made by burning elemental phosphorus.
Previously, the price of phosphoric acid from phosphorus was too high for it to be considered as a fertilizer material. Most of the phosphorus is used to make chemicals that are marketed at a higher price than fertilizers.
The liquid mixed fertilizer industry currently appears to be in a
period of market development and early growth. Many plants are operated only during the sales season and some plants are additions to existing solid fertilizer businesses. Different types of processing and marketing techniques are being carried on and tested.
The present study points out some of the economic factors in evaluating liquid mixed fertilizers and suggests methods of taking them into account. The cost and price data developed for this purpose are only illustrative and cost and price data developed for most commercial situations are expected to be different from those in this chapter.
'Acknowledgment is made to P. W. Roden of the Development Branch for assistance in making the estimates.
Z. A. STANFIELD
The method used for the purpose of the present study was to compare the relative economics of the manufacture of liquid and solid mixed fertilizers. Estimates were made of the investment and production costs for hypothetical new complete plants and of the hypothetical selling prices for various grades of fertilizers made in these plants. Information on process technology was obtained from the literature for the liquid products and from TVA pilot-plant work for the solid products. The study was based on (a) purchase of raw materials at current market prices, (b) conversion of these materials to finished products,
(c) storage of the finished products at the manufacturing plant in forms suitable for sale to distributors, and (d) distribution of products to the consumer.
Assumptions for Estimates
The estimates were made for five different sales volumes: 2,500, 5,000, 10,000, 20,000, and 40,000 tons of product per year. For each sales volume, three types of operation were assumed. in the first case, the plant was designed for seasonal operation with provision for only 2 days of product storage. In the second case, the plant was designed for operation 6 months per year with provision for storage of 20 percent of the sales volume. In the third case, the plant was designed for operation 12 months per year with provision for storage of 40 percent of the sales volume. These variations were selected in order to determine the economic effects of scale and method of operation.
The acid- neutralization method was selected for the manufacture of liquid mixed fertilizers. By this method, phosphatic fertilizer solution is neutralized with ammonia. Other nitrogenous materials, such as urea and ammonium nitrate, are added to increase the ratio of nitrogen to P205 in the product. Potassium chloride is added to provide -20. Sufficient water is added to dissolve the salts that are formed in the reactions and to make the desired grade of product. It is desirable to produce neutral solutions so that low cost steel tanks can be used to store and transport the products. Product grades assumed for the study were 10-10-10, 5-10-10, and 8-24-0. Grades with concentrations higher than those selected do not appear practical using existing known technology.
The process selected for the manufacture of solid mixed fertilizers was that in which the TVA-type continuous ammoniator is used (1). In this process, superphosphate are ammoniated with nitrogen solutions and other materials are added in the ammoniator to make the desired grades. The ammoniator product goes to a granulator and then to a ' rotary dryer. In making some grades, the dryer is not required. The product is sized and the oversize and fines are recycled. Product of the desired size is stored in the product-storage building and is shipped either bulk or bagged. Product grades assumed for the study were 10-10-10, 15-15-15, 6-12-12, 10-20-20, and 8-24-0.
ECONOMICS OF MANUFACTURE
It was assumed that plants would be located in the South Atlantic and Pacific regions. The former was selected because of its established solid mixed fertilizer industry, high rate of fertilizer consumption, and relatively low price of superphosphate. The latter region was selected because of its rapidly expanding fertilizer industry, present low rate of fertilizer consumption, and relatively high price of superphosphate. Conditions in the South Atlantic and Pacific regions appeared to be typical of conditions that are least favorable and most favorable, respectively, for liquid mixed fertilizers. Conditions in other regions probably are intermediate between the two regions selected.
Estimates of cost of construction of process plants and storage facilities were based on typical 1955 conditions. These estimates were made for comparative purposes only, and it is probable that plant estimates made for an actual set of particular conditions would be somewhat different from these estimates. The same method of estimating was used for both processes. The estimates included provisions for process equipment, raw material storage, product storage, buildings, engineering, and construction supervision costs equal to 10 percent of physical cost, and an item for contingencies equal to 20 percent of physical cost. Working capital was calculated as being equal to one month's production cost.
Estimates of production cost were prepared for each assumed
method of operation and sales volume. Typical current market prices for the raw materials in each region were used. The most economical formulation was used for each grade of product. Operation labor schedules were prepared for each set of conditions and average rates of pay for each class of work were used. Seasonal use of labor was assumed in appropriate cases. Estimated costs of utilities, supplies, chemical analyses, and plant overhead were included. Estimates of costs for depreciation, property tax, and insurance were included in production cost.
Estimates of manufacturer's selling price were made for each case. Selling price was assumed to be equal to the sum of production cost, selling expense of $3.00 per ton of product in each case, and 30 percent annual pretax return on total investment including working capital. The basis for prices of liquids was f.o.b. works loaded in tank cars or tank trucks for shipment. The basis for prices of solids was f.o.b. works, bagged and bulk, loaded in cars or trucks for shipment.
RESULTS OF ESTIMATES
Effect of Sales Volume
Estimated selling prices of liquid and solid 10-10-10 fertilizers for the South Atlantic and Pacific regions are shown in figures 7.1 and 7.2. The estimates showed that sales volume had a considerable effect on the selling prices for both the liquid and solid products. The estimated selling prices at the annual sales volume of 2,500 tons were about 40
Z. A. STANFIELD
percent higher than those at the annual sales volume of 40,000 tons. These results indicate that a small producer of either liquid or solid mixed fertilizers would be at a competitive disadvantage in comparison with large producers. The disadvantage of being a small producer is somewhat less for liquids than for solids.
There was a significant decrease in estimated unit capital cost with increase in sales volume for both types of plants. For example, using the 10-10-10 grade and 6 month's operation for two shifts, 6 days per week, as a basis, estimated process plant costs for the liquid plants decreased from $25.00 per annual ton at the 2,500-ton sales volume to $4.00 per annual ton at the 40,000-ton sales volume. Estimated process plant costs for the solid plants decreased from $40.00 per annual ton at the 2,500-ton sales volume to $10.00 per annual ton for the 40,000-ton sales volume. The estimated costs of product storage facilities varied from $16.00 to $5.00 per annual ton for the liquid fertilizer plants and from $3.20 to $3.00 per annual ton for the solid fertilizer plants for the smallest and largest sales volumes, respectively.
It is expected that investment cost estimates based upon designs for specific conditions could be developed for both liquid and solid plants that might be 25 to 50 percent lower than those used in this study. However, for the purpose of comparing the processes, the estimates of this study appear to be adequate. Decrease or increase of the investment costs used by 50 percent did not change the relative economic position of the processes. The wide variation of unit capital cost with sales
SELLING PRICE, $/UNIT OF PLANT NUTRIENT,
F 0. B. MANUFACTURING PLANT
SALES VOLUME, TONS/YEAR
sales volume and seasonal operation on selling price in
South Atlantic region.
Fig. 7.1 - Effect of
ECONOMICS OF MANUFACTURE
SELLING PRICE, S/ UNIT OF PLANT NUTRIENT,
V FO.B. MANUFACTURING PLANT
2.80
PACIFIC REGION
2.60 10-10-10 FERTILIZER BAGS
2.40I BULK
LIQUID SOLID
2.20 __2.00
1.80
1.60
1.40
.20 204
0 20 40 0 20 40 0 20 40 0 20 40 0204
2,500 5,000 10,000 20,000 40,000
SALES VOLUME, TONS/YEAR
Fig. '7.2 - Effect of sales volume and seasonal operation on selling price in Pacific region.
volume for both types of plants suggests the importance of careful consideration of initial capital cost.
The effect of size of plant on operating cost is shown in table 7.1. For the liquid mixed fertilizers, the operating cost decreased from $10.59 to $3.23 per ton for increase in sales volume from 2,500 to 40,000 tons per year. A greater decrease was shown for the solid mixed fertilizers; the operating costs (excluding costs of bags and bagging) were $17.20 and $4.63 per ton, respectively, for the 2,500-ton and 40,000-ton sales volumes. The estimates indicate that for 10-10-10 the advantage for liquids is about 5 cents per unit at the 40,000-ton sales volume and 22 cents per unit at the 2,500-ton sales volume.
Table 7.1. Effect of Plant Size on Operating Costs In Liquid and Solid Mixed Fertilizer Plants
Operating Cost,
$ per Ton Product
Sales Volume, Solid
Tons per Year Liquid (Excluding Bags)
2,500 10.59 17.20
5,000 9.34 10.81
10,000 8.60 9.68
20,000 5.39 7.10
40,000 3.23 4.63
Effect of Product Storage
The effect of providing for storage of different percentages of a given sales volume was different on prices of liquid mixed fertilizer than it was on prices of solid mixed fertilizer. For liquids, the lowest price was obtained for the 3-month operating period, in which case there was no provision for seasonal storage of product. For solids, the lowest price generally was obtained for the 6-month operating period, in which case provision was made for storage of 20 percent of the annual production.
Comparisons between liquids and solids were made on the basis of providing seasonal storage of 20 percent of the annual sales volume even though the lowest estimates of prices for liquids were obtained when no seasonal storage was provided. Operation of liquid mixed fertilizer plants with provision for some seasonal storage appeared to be the most likely case. Seasonal operation merely pushes the storage problem back onto the manufacturer of raw materials (phosphoric acid, ammonia, etc.). A great increase in the storage requirement of these materials probably would result in premium prices for in-season delivery.
Formulation Costs
The estimated costs of raw materials (formulation costs) for 10- 10-10, 6-12-12, and 8-24-0 solidgrades and 10-10-10, 5-10-10, and 8-24-0 liquid grades for both regions are shown in table 7.2. For the South Atlantic region, the formulation costs of solid grades were significantly lower than the formulation costs of the liquid grades of comparable plant nutrient ratio and were 28, 26, and 23 cents per unit lower for the 1:1:1, 1:2:2, and 1:3:0 ratios, respectively. For the Pacific region, the formulation cost of 10-10-10 was 10 cents per unit lower for solids; for the 1:2:2 ratio, liquid and solid formulation costs were about the same; and for the 1:3:0 ratio, the formulation cost of liquid was 10 cents per unit lower for the liquid. In this comparison the position of liquids with respect to solids was improved with decrease of N:P2% ratio. The improvement was most pronounced for the Pacific region.
Table 7.2. Formulation Costs for Several Grades of Liquid and Solid Mixed Fertilizer
Cost of Raw Materials, $ per Unit
South Atlantic Pacific
Solid Liquid Solid Liquid
10-10-10 1.08 1.36 1.33 1.43
5-10-10 - 1.19 - 1.21
6-12-12 0.93 - 1.19
8-24-0 1.25 1.48 1.58 1.48
Z. A. STANFIELD
The major factor causing the different results obtained for the two geographic regions was the difference in prices of the superphosphate for the two regions. The price used for superphosphate was $18.00 per ton for the South Atlantic region and $30.00 per ton for the Pacific region. The effect of the $12.00 difference was to make the price of solid 10-10-10 $6.24 per ton (21 cents per unit) higher in the Pacific region.
These results indicate that a reduction in the market price of phosphatic fertilizer solution below that used in the estimates could place liquid mixed fertilizer in a more competitive position in the South Atlantic region. Calculations indicated that the price of solution would have to be cut about 10 percent for the selling price of liquid 10-10-10 to be the same as that of bagged solid 10-10-10.
Eff ect of Concentration
The effect of increasing the concentration of solid grades in the Pacific region is shown in table 7.3. The estimated selling price of liquid 10-10-10 was 13 cents per unit lower than the price for bagged solid 10- 10- 10. However, the estimated price of liquid 10- 10- 10 was the same as the price of bagged solid 15-15-15 made using concentrated superphosphate. The price of liquid 5-10-10 was 15 cents per unit lower than the price of bagged solid 6-12-12. However, the estimated price of liquid 5-10-10 was 6 cents per unit higher than the price of solid 10-20-20 made using concentrated superphosphate.
Effect of Geographic Area
The results plotted in figures 7.1 and 7.2 show that the estimated selling price of liquid 10-10-10 was higher than either bulk or bagged solid 10710-10 in the South Atlantic region for sales volumes of 5,000 tons per year or more; it was about 4 percent higher than bagged and about 11 percent higher than bulk solids. In the Pacific Coast region,
Table 7.3. Effect of increasing Concentration of Solids
Manufacturer's Selling
Price, $ per Unit,
Pacific Region
Bagged solid 10-10-10 1.89
Bagged solid 15-15-15 1.76
Liquid 10-10-10 1.76
Bagged solid 6-12-12 1.75
Bagged solid 10-20-20 1.54
Liquid 5-10-10 1.60
ECONOMICS OF MANUFACTURE
Table 7.4. Estimates of Selling Price of 10-10-10 Liquid and Solid Fertilizer
(Sales Volume, 40,000 Tons per Year; Plants Operated 6 Months per Year to Produce 40,000 Tons)
Item
Anhydrous ammonia Nitrogen solution,
40.6% N
Ordinary superphosphate
Phosphoric acid,
75% H3P04 Urea
Potassium dhloride Sulfuric acid Water
Filler (sand)
Total raw materials
Operating labor Maintenancea Electricity Supplies, 2% operating
labor
Analyses Property tax, 1% plant
investment
Insurance, 1 %plant
investment
Depreciation, 10%
process plant and 5%
storage investment Plant overhead,
1 0% operating labor Bags and bagging Total operating cost Total production cost
Selling expense Return, 3 0% of total
investment
Selling price, f.o.b.
plant, $/ton product Selling price, f.o.b.
plant, $/unit plant food
Process plant Product storage Working capital
Total investment for return
South Atlantic Region Pacific Region
$ per Ton Product $ per Ton Prod
$/Ton Solid Solid $/Ton Solid Solid
Material Bulk Bagged Liquid Material Bulk Bagged L
95.00 - - 3.80
60.00 15.30 15.30
18.00 9.36 9.36
85.00 - - 15.73
101.00 - - 14.95
37.75 6.42 6.42 6.42 18.00 1.33 1.33
0.02 - - 0.01
3.00 0.10 0.10
32.51 32.51 40.91
1.23 1.23 1.20 0.67 0.67 0.17
0.40 0.40 0.20
0.02 0.02 0.02 0.20 0.20 0.20
0.14 0.14 0.09
0.14 0.14 0.09
95.00
62.00
30.00
85.00
114.00 37.75 25.00
0.02 3.00
1.21 1.21 0.66 0.62 0.62 0.60
- 4.00
4.63 8.63 3.23 37.14 41.14 44.14
3.00 3.00 3.00 5.09 5.09 3.92
45.23 49.23 51.06
1.51 1.64 1.70 investment Cost, $/Annual Ton
Solid Liui
10.60 4.12
3.00 5.00
3.35 3.92
16.95 13.04
15.81 15.81 15.60 15.60
6.42 6.42 1.85 1.85 0.10 0.10
39.78 39.78 1.23 1.23 0.67 0.67
0.40 0.40 0.02 0.02 0.20 0.20 0.14 0.14 0.14 0.14
ict quid 3.80
15.73 16.87
6.42 0.01
42.83 1.20 0.17
0.20 0.02 0.20 0.09 0.09
0.62 0.62 0.60
- 4.00
4.63 8.63 3.23 44.41 48.41 46.06 3.00 3.00 3.00 5.27 5.27 3.97 52.68 56.68 53.03 1.76 1.89 1.76
aFor liquid plants: 3 percent process plant investment plus 1 percent storage investment. For solid plants: 6 percent process plant Investment plus 1 percent storage investment.
ECONOMICS OF MANUFACTURE
the price of liquid 10-10-10 was about 6 percent lower than bagged solid 10-10- 10 and about the same as for bulk solid. These small differences indicate that specific locations probably could be found where the manufacture of liquid and solid 10-10-10 would be closely competitive, economically, in both regions especially at the larger sales volumes.
Typical estimates of selling prices of 10- 10- 10 liquid and solid mixed fertilizers are shown in table '7.4. The 40,000-ton-per-year sales volume was selected for this comparison because the lowest unit costs for both liquid and solid were obtained for this sales volume. From this table it is observed, in the South Atlantic region, the advantages of lower operating cost and lower investment cost for liquids were not enough to overcome the disadvantage of higher formulation cost. In the Pacific region, the disadvantage in formulation cost for liquid 10-10-10 was not so great as in the South Atlantic region and this disadvantage was overcome by lower operating and investment costs.
Table 7.5. Estimated Costs of Distribution of Solid and Liquid Fertilizers
(Sales Volume: 5,000 Tons; Cost Delivered to Farm)
n agged Solid Liquid
Item Description $/Ton Description $/Ton
Labor 4 drivers at $2.30/hr. 1.32 10 drivers, 25% of time, 0.83
at $2.30/hr.
Maintenance 5%/yr. of equipment cost 0.09 5%/yr. of equipment cost 0.24
Fuel Gasoline 0.30 Gasoline 0.19
Supplies 5 %of labor cost 0.07 5 %of labor cost 0.04
Property tax and
insurance 5% of investment 0.16 5 %of investment 0.27
Office overhead 50 %of labor 0.66 50% of labor 0.42
Depreciation 0.60 1.31
Operating cost 3.20 3.30
Administrative
expense 1.00 1.00
Return on Investment 1.86 2.55
Total cost of distribution 6.06 6.85
Freight, manufacturer to distributor 4.00 4.00
Total cost delivered to farm 10.06 10.85
Investment
Amount Amount
Charged to Charged to
Fertilizer Fertilizer
Trucks Four 10-ton trucks Seven 2000-gal, trucks
at $6000 = $24,000 $ 6,000 at $10,000 = $70,000 $17,500
Storage and office 1 week 20,000 3 days 20,000
Working capital 1 mo. operating cost 5,000 1 inn. operating cost 5,000
Total investment for return $31,000 $42,500
Distribution Costs
In order to make a general comparison of the prices of the several products delivered to the farm, rough estimates were made of the cost of distribution of liquid and bagged solid fertilizers. A breakdown of the estimated distribution costs is shown in table 7.5. In these estimates it was assumed that the annual sales volume of 40,000 tons would be distributed by eight distributors each handling 5,000 tons of product per year. It was assumed that each distributor would be located 100 miles from the manufacturing plant and would deliver to farms located (on the average) 20 miles from the distribution point. Investment and operating costs for the distributor were prepared in which the distributor was allowed a profit equal to 30 percent per year of the estimated investment.
The estimates indicate that the costs of delivering fertilizer from the manufacturing plant to the farm would be $10.00 per ton forte bagged solids and $11.00 per ton for liquids. For fertilizers of the same concentration, the difference probably is not significant. However, distribution costs per unit of plant nutrient would decrease with increase in concentration of fertilizer. This fact could b6 important in the choice of process since higher concentrations cannot be attained with liquid
Table 7.6. Estimated "Delivered to Farm" Selling Prices for 40,000-Ton
Annual Sales Volume (one Manufacturer and Eight Distributors)
Estimated Delivered Price to Farm $/Unit South Atlantic Region Pacific Region
Grade of Bagged Bagged
Product Solid Liquid Solid Liquid
1:1:1 Ratio
10-10-10 1.97 2.05 2.22 2.12
(1.64) (1.70) (1.89) (1.76)
15-15-15 1.88 1.98
(1.66) (1.76)
1:2:2 Ratio
5-10-10 1.99 2.03
- (1.58) - (1.60)
6-12-12 1.82 2.08
(1.49) (1.75)
10-20-20 1.65 10 1.74
(1.45) (1.54)
1:3:0 Ratio
8-24-0 2.11 2.14 2.44 2.14
(1.79) (1.80) (2.12) (1.80)
Note: Figures in parentheses are prices f.o.b. manufacturing plant.
Other figures are prices delivered to farm.
Z. A. STANFIELD
ECONOMICS OF MANUFACTURE 71
mixes because of solubility limitations. Estimated delivered prices of several grades of liquid and solid fertilizers are shown in table 7.6.
REFERENCES CITED
1. HEIN, L. B., HICKS, G. C., SILVERBERG, JULIUS, and SEATZ, L. F., 1956.
J. Agr. Food Chem. 4, No. 4, 318-30.
2. JACOB, K. D., and SCHOLL, WALTER, 1955. Commercial Fertilizer Yearbook, 94-107.
3. LANGGUTH, R. P., PAYNE, J. H., Jr., ARVAN, P. G., SISLER, C. C., and BRAUTIGAM, G. F., Jr., 1955. 5. Agr. Food Chem. 3, No. 8, 656-63.
4. SLACK, A. V., 1955. J. Agr. Food Chem. 3, No. 7, 568-74.
EARL R. SWANSON
University of Illinois
Chapter 8
Programming a Fertilizer
Mixing Operation
INEAR programming is being applied to an increasing number of
problems which involve quantitative aspects of management decisions. This chapter illustrates the application of the technique to the problem of mixing a fertilizer to meet a certain set of requirements with a minimum expenditure for ingredients. Once the requirements for the fertilizer and the composition and cost of the plant food carriers have been specified, linear programming unfailingly provides the minimum cost mix. The theoretical basis of linear programming, as well as the computational methods, has been treated elsewhere (1, 3).
Consider the problem of mixing a formula containing N, PO, and KO. If each carrier considered contained only N, P205 or K20 the several sources of, say N, could be evaluated on the cost per pound of N and the least expensive source chosen. A similar procedure could be followed for choosing the carriers of P20. and K20. The resulting mix would then be the least expensive one considering all of the carriers which contain only a single plant food. However, the mixer may also wish to consider carriers which contain more than one plant food. It the plant food ratios in the carriers considered as possible ingredients for the mix are not in the same proportions, the problem of evaluating the least expensive sources becomes difficult. Further, as requirements regarding the physical properties of the mix are added, the problem becomes even more complex. By casting the problem in a linear programming form for solution, one can be assured that the minimum cost mix will be systematically selected and that the specified requirements are met.
REQUIREMENTS
As an illustration of application of the linear programming technique, suppose that a mixer wishes to blend several carriers into a ton of 4-12-4 mixed fertilizer. The fourteen available carriers are listed in table 8. 1. The mixer also desires that the product be neutral, that is, neither acid'nor basic. He also wishes to insure drillability of the final product.
Letting the quantities of the materials be designated as xi
PROGRAMMING A FERTILIZER MIXING OPERATION
Table 8.1. Composition of Fertilizer Materiala
Water - Equivalent Acidity (A) Available Soluble or Basicity (B) in
Fertilizer Material N P205 KO Pounds of CaCO3
i ai bi di k
(Percent) (per 100 Pounds Material)
1. Ammonium nitrate 32.5 -- 60A
2. Ammonium sulfate 20.5 -- 110A
3. Calcium cyanimid 22.0 -- 63B
4. Calcium limestone - -- 90B
5. Castor pomace 6.0 1.5 0.5 6A
6. Cottonseed meal 6.6 2.5 1.5 10A
7. Dried blood 13.0 - - 23A
8. Fish scrap (dried) 9.5 6.0 - 7A
9. Manure salts - - 25.0
10. Muriate of potash - - 60.0
11. Sand - -
12. Sulfate of potash
magnesia - - 26.0
13. Superphosphate - 20.0
14. Tankage 7.0 - -13B
aSauchelli, Vincent, 1946. Manual on fertilizer manufacture. The Davison Chemical Corporation, Baltimore, Table 2, p. 19 and Table 39, p. 88.
(i = 1, 2, 3,., 14), the total quantity of mixed fertilizer that is to be produced is specified. In this case one ton will be produced; hence:
14
(8.1)Z xi = 2,000 pounds i=1
The formula of the mixed fertilizer to be produced must, of course, be considered as a requirement. In this example, assume a production of a 4-12-4 mixed fertilizer;. thus there must be at least 80 pounds of N, 240 pounds Of P205, and 80 pounds of K20 in the mixture. Letting a1 equal the percentage of N, bi equal the percentage Of P205 and di equal the percentage of K20 in each of the 14 ingredients, the formula requirement may be written as follows:
14
(8.2) aixi > 80 pounds
14
(8.3) E bix1 > 240 pounds
i=1 -
EARL R. SWANSON
14
(8.4) dixi > 80 pounds
Letting the equivalent acidity or basicity in pounds of CaCO3 (table
8.1) be designated as ki one may write the neutrality restriction as follows:
14
(8.5) Z~ kixi 0
1=1
where opposite signs are attached to the acidity and basicity equivalents.
The drillability requirement may be met by specifying the maximum and minimum quantities of certain nitrogen carriers. In this case it is specified at least 13 pounds of N must come from organic sources:
(8.6) a3x3 + asx5 + a4x6 + a7x7 + a8x8 + a14X14 > 13 pounds
where the subscripts refer to the ingredient numbers in table 8. 1. In addition, the quantity of N that may be obtained from ammonium nitrate is restricted to 35 pounds. Hence:
(8.7) aixi < 35 pounds
COST CONSIDERATIONS
The requirements stated above could be satisfied by a large number of combinations of the 14 ingredients. The single combination which minimizes ingredient cost is insured by the linear programming method.
Table 8.2. Price Situations Used to Compute Materials Needed to Minimize Cost of a Ton of Neutral 4 -12 -4
Price Situations
Fertilizer Material I II inI IV V VI VII
(Dollars per Ton Delivered to Mixing Plant) Ammonium nitrate 70.00 80.00 60.00 80.00 70.00 50.00 60.00
Ammonium sulfate 60.00 70.00 50.00 70.00 80.00 40.00 60.00
Calcium cyanimid 70.00 60.00 80.00 150.00 150.00 120.00 130.00
Calcium limestone 3.50 4.00 3.00 5.00 3.50 2.00 4.00
Caster pomace 32.00 30.00 34.00 30.00 40.00 40.00 35.00
Cottonseed meal 80.00 60.00 100.00 60.00 60.00 35.00 40.00
Dried blood 140.00 120.00 160.00 120.00 90.00 70.00 75.00
Fish scrap (dried) 110.00 80.00 140.00 80.00 70.00 60.00 55.00 Manure salts 20.00 15.00 25.00 15.00 20.00 20.00 15.00
Muriate of potash 40.00 45.00 35.00 45.00 40.00 50.00 35.00 Sand 3.50 2.00 5.00 2.00 3.00 3.50 3.00
Sulfate of potash
magnesia 32.00 25.00 39.00 15.00 20.00 20.00 30.00
Superphosphate 30.00 35.00 25.00 30.00 50.00 40.00 30.00
Tankage 120.00 100.00 140.00 45.00 45.00 80.00 50.00
PROGRAMMING A FERTILIZER MIXING OPERATION
Letting pj indicate the price per pound of each ingredient (table 8.2) the cost, C, may be written as follows:
(8.8)
14
C = x.p
The xi that will minimize the cost and yet furnish the desired product is chosen by linear programming.
RESULTS
Computation of the solutions was performed by using the simplex method (1). The results for seven different price situations are presented in table 8.3.
Several interesting observations may be made concerning the leastcost combinations in table 8.3. For example, in moving from price situation I to II, it is obvious that the nitrogen from calcium cyanimid is cheaper (14 cents a pound) than that from ammonium sulfate (17 cents a pound). However, calcium cyanimid does not completely replace ammonium sulfate due to the requirement of a neutral mixture. Price situation III in table 8.2 results in the same quantities of materials as situation I, even though there has been some change in the prices compared with situation I.
In price situation IV, manure salts are a cheaper source of potash
Table 8.3. Quantities of Materials Needed to Minimize
Cost of a Ton of Neutral 4 -12 -4
Price Situations (See Table 8.2)
Fertilizer Material I HI III IV V VI VII
(Pounds)
Ammonium nitrate 107.7 107.7 107.7 107.7 107.7 107.7 107.7
Ammonium sulfate 156.1 38.1 156.1 156.1 156.1 156.1 156.1
Calcium cyanlmid 59.1 169.0 59.1 22.0 22.0 16.9 16.9
Calcium limestone 221.2 - 221.2 256.2 256.2 266.4 266.4
Castor pomace - - - 136.0 136.0 -
Cottonseed meal - - - - - 140.7 140.7
Dried blood - - - - - -
Fish scrap (dried) - - - - - -
Manure salts - 320.0 - - - -
Murlate of potash 133.3 - 133.3 132.2 132.2 129.8 129.8
Sand 122.6 165.2 122.6 - - -
Sulfate of potash
magnesia - - - - - -
Superphosphate 1,200.0 1,200.0 1,200.0 1,189.8 1,189.8 1,182.4 1,182.4
Tankage - - - - - -
Total 2,000.0 2,000.0 2,000.0 2,000.0 2,000.0 2,000.0 2,000.0
Material cost per ton $31.79 $34.28 $27.47 $34.92 $47.22 $36.45 $32.37
EARL R. SWANSON
than muriate of potash, but they are not used. These two sources of potash have the same price relation in situation IV as in situation A but the manure salts were selected in situation II. When all requirements are considered, the cost per pound of any particular plant food may be misleading. Note also that the least-cost combinations in situations IV and V are the same even though in situation V the nitrogen in tankage is slightly cheaper (32 cents a pound) than the nitrogen in castor pomace (33 cents a pound).
Finally, situations VI and VII result in the same combination of materials. The cost per pound of nitrogen from dried blood in situation VII is 29 cents a pound compared with 30 cents a pound in cottonseed meal. However, cottonseed meal is used because its contribution to requirements other than nitrogen makes the over-all cost of the mixture a minimum. Thus, all of the requirements must be considered in calculating a minimum-cost mixture.
It is possible to determine from a linear programming solution the amount by which the price of a carrier not selected for the mix must fall in order for it to be an ingredient of the minimum cost mixture. In the literature these values are frequently referred to as zj-cj(l). Take as an example the result under price situation I. Note that castor pomace does not appear in the mixture. Examining the zj-c, for castor pomace it is evident that its price would have to drop $8.08 per ton (other ingredient prices remaining the same) in order for it to appear in the minimum-cost mix. Price decreases necessary for selection of other ingredients not presently appearing in the mixture also can be readily determined.
CONCLUDING REMARKS
It is hoped that the relatively simple illustration presented is suggestive of further application of the technique to problems in fertilizer mixing. A more complete analysis would need, of course, to consider costs other than only the ingredients. Such factors as capacities of blending apparatus, baggers, and other machinery may also be included in a more comprehensive programming analysis. Further, in situations where more than one analysis may be mixed it may be also desirable to include choice of the amounts of each analysis to be prepared as a part of the problem.
REFERENCES CITED
1. CHARNES, A., COOPER, W. W., and HENDERSON, A., 1953. An introduction
to linear programming, New York, John Wiley and Sons, Inc.
2. - , - , and MELLON, B., 1952. Blending aviation gasolines, Econometrica 20:135-59.
3. KOOPMANS, T. C., 1951. Activity analysis of production and allocation,
Cowles Commission for Research in Economics, Mono. 13, N. Y., John Wiley
and Sons, Inc.
4. WAUGH, Frederick V., 1951. The minimum-cost dairy feed, Journal of Farm
Economics 33:299-310.
HAROLD G. WALKUP and JOHN N. MAHAN Tennessee Valley Authority
Chapter 9
The Potential Market
for Liquid Fertilizer
INTRODUCTION
UMEROUS considerations should be explored in an investigation
of market potential for a relatively new product such as liquid
fertilizer. First of all, however, it appears appropriate to define what products the authors consider to be liquid fertilizers; second, it seems desirable that market potential considerations be defined. Neither of these topics has become sufficiently staid that its specific universal interpretation is assured. Rather, it appears judicious to develop definitions in line with the investigative aspects of this chapter.
Liquid fertilizers are defined as those fertilizers and fertilizer
materials which, when used by farmers, are completely in water solution or which are not in water solution but being liquid themselves are thus applied either directly to the soil through an irrigation system or other means of water conveyance and application. Hence, it can be seen that liquid mixtures and complete liquid fertilizers, anhydrous ammonia, aqueous ammonia, and phosphoric aci& all can be included.
MARKET POTENTIAL CONSIDERATIONS
Market potential for a product usually refers to the quantity which will be purchased within the confines of an area during a specified period at a specified price or series of prices! The estimation of market potential for a new product is at best a speculative matter. However, there are certain fundamental considerations, particularly for a commodity which is to be used for productive purposes, which are helpful in appraising potential use. This is particularly true for a
'It is difficult to make an adequate and discriminating distinction between liquid and dry type fertilizers. For the purposes of this chapter it appeared to be desirable to distinguish between the liquid and dry types on the basis of their liquid or dry form at the time of application through application machinery on the farm.
'This is an obvious oversimplification of the complexity of the economic aspects of market potential. Additional considerations include such matters ast (a) price relationships between the subject product and competitive, complementary, and supplementary goods; (b) a designated consistency, degree of change or trend in the techniques of production; (c) a continuity of quality of competing products and numerous other considerations which one may call to mind.
H. G. WALKUP AND J. N. MAHAN
product like liquid fertilizer which is nearly a perfect substitute for the
3
older, dry type fertilizers . These fundamental considerations relate to: (a) the costs of new products and their close substitutes; (b) the productivity response of the product when used in enterprises which are currently employed in the area or which may be employed as the result of technical or economic changes within or outside the area under consideration; (c) the continuity or alteration in income flow either on a legal basis or due to social or family sanction. Market potential studies have for the most part been directed toward these fundamental considerations.
Methods of Studying Market Potential
One method frequently used is the survey method whereby a scientif ically drawn sample of respondents from a given population are individually questioned as to their willingness, desire, and ability to pay for various quantities of the product at specified prices. If competitive goods are available, a price reference between the product and competitive goods is usually considered by respondents. Another method frequently employed, particularly with a new product, involves the selection of areas in which the saleability of the product may be tried. Price adjustments may be made within the areas to determine price effects on demand, or similar areas may be charged different prices to estimate price effects. In both methods detailed basic data on income and other pertinent information are collected in the areas being studied for market potential. Statistical studies are sometimes made to develop predicting equations relating to demand. Important variables usually included in these equations are prices of the product and closely competing products as well as measures of income. The use of this method depends to a considerable degree on the existence of an already established market and is not well suited to the examination of a potential where a product has not previously been marketed or only recently introduced.
A closely allied consideration which often should be made in connection with a market potential study relates to the costs required to place the product in the specified marketing areas. In the case of a new product which is closely competitive with an already established product in the selected area, it is usually helpful to compare the costs of placing both products in the area, as a clue to the share of the market each shall receive. Such estimations and interpretations require judicious and comprehensive use of budgeting and farsighted interpretation. Of particular importance is the necessity for detecting those attributes of the competing products which give them uniqueness in the various production situations in the marketing area studied. In the case of
'The term "Perfect substitute" is used in the sense that, when applied to the soil, equal quantities of plant nutrients (N, P, or K) in either the dry or liquid form substitute for one another at a constant ratio of I to 1.
noncompeting but complementary product goods, considerations relating to attributes contributing to production complementarity are of great significance.
HISTORICAL ASPECTS OF FERTILIZER USE
A brief historical consideration of fertilizer use in the United States, although not of primary importance to this study, may lend some perspective to the present technological stage of development in the fertilizer industry.
The use of fertilizers to improve the production of forage and grain crops (3) has a long and interesting history (table 9.1). Until recently, many agricultural areas of the United States have used only animal manures produced on or near the farm on which they were spread. In the older agricultural areas of the United States and particularIy in the southeastern part of the country, commercial fertilizers have been used for a long time. Interestingly enough, the first imported fertilizers were of animal origin. The material was Peruvian guano (bird dung) which was shipped into this country during the 18401s. Slightly more than 100 years ago the first mixed fertilizers were manufactured in the United States and about 8,000 tons of plant nutrients were used annually. By 1900, farmers were using 394,000 tons of plant nutrients in commercial fertilizers.
Organics, ammoniates, dissolved bone or bone black, kanit and
Table 9.1. Plant Nutrient Consumption per Acre of Crops and Pasture Land
Millions of Poundsb Pounds of Primary Average Primary Millions of of Primary Plant Nutrients Applied Plant Nutrient Year Acresa Nutrients per Acre Content (Percent)
1910 631 1,712 2.71 15.7
1920 730 2,290 3.14 16.G
1925 722 2,482 3.44 16.9
1930 792 3,048 3.85 18.5
1935 826 2,430 2.94 19.3
1940 860 3,432 3.99 20.8
1945 932 5,658 6.07 21.4
1950 894 8,828 9.87 24.5
1955 12,506c
'Acreage includes cropland and pasture land in farms. 1953 Agricultural Statistics, b USDA, Table 643, p. 550.
Agricultural Statistics, 1952, USDA, Table 710, p. 705. 'Mehring and Graham, 1955, USDA. Fertilizer situation for 1954-55, Commercial Fertilizer and Plant Food Industry, 90:44 p. 44.
POTENTIAL MARKET FOR LIQUII) FERTILIZER
H. G. WALKUP AND, J. N. MAHAN
hardwood ashes were used in the early mixtures. Even up to the first World War the fertilizer industry was considered to be a scavenger industry, one that absorbed the waste from other industries such as dried blood, fish scrap, hoof and bone meal, animal tankage, process tankage, cottonseed meal, cottonseed hulls, castor pomace, and tobacco stems. Although inorganic sources of plant nutrients were developed, the common belief that organic materials were superior sources of plant nutrients had to be combated with mounting agronomic results and forceful educational programs. World War I unveiled the commercial potash potential in this country. Synthetic ammonia was first produced commercially in 1921. In 1940, there were 9 plants in operation. The Government built 10 plants during Xorld War H. At the present time there are 43 synthetic ammonia plants in the United States. Due apparently to location economics, these are widely scattered throughout the country. Immediately after World War II the fertilizer industry was faced with a larger demand than it could supply at the prices then charged for fertilizer. A program for governmental assistance to the fertilizer industry was initiated in 1951 so that our food and fiber needs could be
4
met.
Technological Improvements in Fertilizer and
Other Industries Related to Agriculture
There is one notable difference between the technological development of the fertilizer industry as it affects farmers, as compared to many other industries which are closely related to agriculture. Although fertilizers now contain more nutrients per ton, the techniques farmers may use to handle them have changed but little. Most fertilizer is sold in bags and the bags must be handled manually several times before the fertilizer gets on the land. Maintaining proper physical condition in dry types of fertilizers further aggravates the problem. A wider acceptance of bulk handling may facilitate convenient and efficient handling of fertilizers on farms. However, it appears that liquefaction of fertilizers and handling with pumps and valves offers much promise to convenience and perhaps to economy in application.
Liquid metering devices are much more accurate than the gates used to regulate rates of application for dry fertilizers. Also equipment for applying liquid fertilizers may have accessories for applying fumigants, insecticides, pesticides, and defoliants which help spread the fixed cost of equipment. In addition, the rate of application is twice as great as for solid fertilizer.
4 The expansion of fertilizer production facilities was encouraged by the Defense Production Act of 1950. Under this program certificates were granted for rapid depreciation of assets for tax purposes. Goals were established during the period when certificates were granted as follows: for nitrogen, 3,500,000 tons; for phosphate (P200, 3,550,000 tons; for potash (K20), 2,000,000 tons.
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