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Bulletin 607
February 1959
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
J. R. BECKENBACH, Director
GAINESVILLE, FLORIDA
Irrigation of Whiteclover-Pangolagrass
Pasture for Dairy Cows
SIDNEY P. MARSHALL and J. MOSTELLA MYERS
Fig. 1.-Quality whiteclover forage on an irrigated pasture being grazed
in strips to obtain maximum production.
CONTENTS
Page
IN TRODUCTION ............................................................................... 3
REVIEW OF LITERATURE ................................................. ........ 4
METHOD OF PROCEDURE .......-..... ....-..---...-........... ....-....-...- 5
EXPERIMENTAL RESULTS ...---......... -......---.---........--........... 7
Rainfall and Irrigation W ater Applied -...-................. ....... ....- ..-- 7
Grazing Periods and Total Digestible Nutrients Obtained Per Acre.. 9
Distribution of the Feed Supply and Carrying Capacity
of the Pastures .................... ... ... .... ..... ..- ....... ... .. 11
Composition of Forage Samples ...............--.... .......... .............. 13
Milk Production, Body Weight Changes and Percent of Required
Total Digestible Nutrients Obtained From Pasture ............-..-.. 15
Hay Equivalents Obtained from the Pastures ...................................... 16
Calculated Production Costs and Feed Replacement Values ........-.. 16
D IscussION ............. ..-............... ......... ......... ... ......... ... ...- ... 19
SUMMARY AND CONCLUSIONS ...........- -....... ..---.-.---.--. ..- .-- 21
ACKNOWLEDGMENTS .... ......... .- .... .. ------- -------.. .- ---..--- 22
LITERATURE CITED ............ ... ......................-...--- ---.--.-.-... -. --.--- 22
Irrigation of Whiteclover-Pangolagrass
Pasture for Dairy Cows
SIDNEY P. MARSHALL and J. MOSTELLA MYERS
Dairy Husbandman and Associate Agricultural Engineer
INTRODUCTION
Pastures are a comparatively inexpensive source of feed and
dairy cattle can utilize large amounts of high quality forage in
satisfying their nutritive requirements. In Tennessee (5)1 high
quality pastures alone supported 88 percent as much milk pro-
duction as was obtained by supplementing the pasture with a
"normal" concentrate allowance of 5.8 pounds daily per cow. In
Florida production costs averaged only 1.5 cents per pound of
total digestible nutrients obtained from permanent pastures on
19 dairy farms (11).
Pastures have furnished a relatively small proportion of the
total nutrient intake of Florida dairy herds. A state-wide sur-
vey (15) revealed that pastures furnished 25 percent of dairy
cattle feed requirements during the five-year period 1951-1956.
During the warmer season of March through October, pastures
supplied 30 percent of the requirement with a high of 36 percent
during the month of July. The proportion of feed obtained from
pasture could be increased profitably to at least 50 percent and
without any decline in milk production, according to an analysis
made of Florida Dairy Herd Improvement Association records
(11).
Concentrates, which are more expensive, were the principal
source of nutrients fed. Hay and other roughages fed averaged
only 3.7 pounds daily per animal during the 1951-1956 period.
Concentrates fed per 100 pounds of milk produced in 1953-54
averaged 77 pounds in Florida DHIA herds, as compared with
only 30 pounds for the herds in all states reporting (14).
The pasture acreage of dairies in the Florida peninsula was
estimated to average 0.8 acre of native and 0.8 acre of improved
pasture per cow in 1953 (12). Total digestible nutrients obtained
from these pastures were estimated at 787 pounds per acre. Some
reasons indicated for the low total digestible nutrient yield were:
inadequate fertilization, extensive type grazing management
practices and poor management. Increases in amounts of feed
1 Italic figures in parentheses refer to Literature Cited.
Florida Agricultural Experiment Stations
obtained from pastures will have to come primarily through in-
tensification, since adjacent suitable pasture lands frequently
are not available and there is a trend towards enlargement of
herds. Therefore, this study was undertaken to determine the
yield of total digestible nutrients, quality, distribution of feed
supply and net returns that may be realized from irrigated and
unirrigated pastures under intensive grazing management and
liberal fertilization programs.
REVIEW OF LITERATURE
Dairy heifers gained 32 percent more in weight and grazed
34 percent more days on irrigated grass-legume pasture than on
unirrigated pasture during two years at the University of Geor-
gia (3). Cows obtained an average of 2,600 pounds of total
digestible nutrients per acre annually from irrigated grass-
legume pasture, as compared with 1,707 pounds from the un-
irrigated pasture during a four-year period at the Middle Ten-
nessee Station (4). In North Carolina (10) cows grazed an
average of 3,037 pounds of total digestible nutrients per acre
from irrigated fescuegrass-ladinoclover and 1,999 pounds from
the unirrigated pasture annually during two years of trials.
Irrigated orchardgrass-ladinoclover pasture furnished an av-
erage of 4,099 pounds of total digestible nutrients per acre an-
nually, while unirrigated pasture supplied an average of 2,557
pounds during four years of trials at Lewisburg, Tennessee (16).
The pasture season was 207 days, but grazing on the unirrigated
area was interrupted by drought in two years.
Irrigation improved the reliability of whiteclover-mixed grass
pastures as winter and spring forage crops in Florida (7). An-
nual gains of beef cattle averaged 810 pounds per acre on the
irrigated pasture and 294 pounds per acre on the unirrigated
during three years of trials.
Steer gains on fertilized bluegrass-whiteclover pastures av-
eraged 422 pounds per acre on irrigated and 353 on unirrigated
pasture during two years in Kentucky (13). Lamb gains during
two following years averaged 450 pounds on the irrigated and
253 pounds on unirrigated pasture.
Animal gains averaged 347 pounds per acre on irrigated grass-
legume pasture and 236 pounds on the unirrigated mixed pasture
during six years in Illinois. The authors concluded that man-
agement practices must be improved if returns from irrigated
pastures are to pay the cost of irrigation (6).
Irrigation of Whiteclover-Pangolagrass Pasture
METHOD OF PROCEDURE
Whiteclover-pangolagrass pasture established in 1950 on
Scranton loamy fine sand at the Dairy Research Unit, Hague,
Florida, was divided into four comparable one-acre plots prior
to the beginning of the experiment in 1952. The alternate two
plots were irrigated and the others served as unirrigated con-
trols. In January 1953 each plot was subdivided, making four
irrigated and four unirrigated areas during 1953 and 1954. In
1955 a one-acre irrigated and one-acre unirrigated plot were used.
Fertilization and management practices for unirrigated and
irrigated plots were comparable except for the supplemental
water applied to the irrigated areas. Two tons of ground agricul-
tural limestone were applied per acre prior to establishing the
pasture in 1950 and the pH of soil samples taken in the fall was
6.2 in 1952, 6.0 in 1953 and 5.8 in 1954. An application of 1.2
tons of ground agricultural limestone was made in fall of 1954,
following the soil test. Superphosphate was applied annually in
the fall; applications of muriate of potash were made in the fall,
winter and spring; and nitrogen top-dressings were made during
the spring, summer and fall. Amounts of phosphorus, potash
and nitrogen applied per acre each pasture season are shown in
Table 1. The pastures were mowed when necessary to control
weeds or cut clumps of forage that had not been grazed adequate-
ly. It was necessary to scatter cattle droppings following most
rotations in order to minimize forage refusal in areas of heavy
manure accumulation.
TABLE 1.-PHosPHORUS, POTASH AND NITROGEN APPLIED PER ACRE TO
IRRIGATED AND UNIRRIGATED PLOTS FOR EACH PASTURE YEAR.
Nutrients, Pounds per Acre Av. Number N
Year N Top-dressings per Plot
PO, K2O N |
1951-52 127 180 142 6
1952-53 90 180 193 6
1953-54 100 210 226 5
1954-55* 100 180
Grazing discontinued May 31.
Water from a shallow well was applied on the pastures with a
portable overhead-sprinkler irrigation system at the approximate
rate on one-half inch per hour. Applications were made when
Florida Agricultural Experiment Stations
about 75 percent of the available moisture had been removed
from the top six-inch layer of soil. The water applied each irri-
gation was the amount necessary to restore the moisture level
to field capacity in the top 18 inches of soil. Moisture determina-
tions were made by oven drying soil samples. Percentages of
soil moisture at field capacity and at permanent wilting are
shown, for different soil depths, in Table 2.
TABLE 2.-AVERAGE SOIL MOISTURE PERCENTAGE AT FIELD CAPACITY
AND PERMANENT WILTING.
Soil Moisture Percentage
Depth in Inches
Field Capacity Permanent Wilting
0-1 ...-...... ...- ...- ... ........ 14.0 4.0
2-6 ..... ......... ......... 12.0 4.2
7-11 .. ... --.. .. ........... 10.0 3.8
14-18 .......... ..........-... ... 9.0 3.4
In the spring of 1955 the irrigation procedure was altered to
observe the effect of maintaining soil moisture near or above
field capacity, in the entire whiteclover root zone, on the amount
of feed obtained from the pasture. From March 1 through May
31 water as rainfall or irrigation was available to the irrigated
pasture at two- to three-day intervals in amounts to supply an
average of about 0.3 inch per day.
The irrigated and unirrigated pastures were grazed beginning
March 18, 1952, although irrigation could not be started until
April 18. Differences in the pastures resulting from irrigation
were established by June 1 and the comparative study, begun at
that time, was continued for three years.
Separate, comparable groups of lactating cows were used to
graze the irrigated and unirrigated pastures. Grazing was be-
gun when the clover was about seven inches high and was con-
tinued into the fall until frost or until forage growth was in-
adequate to justify pasturing the cattle. The plots within each
treatment were grazed rotationally the first three years. In
1955 the plot within each treatment was grazed rotationally by
narrow strips (8). The number of cows grazing the irrigated
or unirrigated pastures was adjusted according to the available
supply and anticipated growth of forage. The animals were kept
on the pastures continuously except when removed for milking.
Irrigation of Whiteclover-Pangolagrass Pasture
Shade, drinking water and an iron-copper-cobalt mineral mixture
were provided in each plot.
The cows were milked twice daily and production was re-
corded. Butterfat tests were made on an aliquot of one day's
production at the beginning and at biweekly intervals during
the experiment. The cows were weighed following the afternoon
milking on three consecutive days at the beginning and end of
the experiment and at 28-day intervals during the experiment.
The concentrate feeding plan generally followed was to offer
1 pound of the mixture containing 16 percent of crude protein per
3.5 pounds of 4 percent fat-corrected milk produced. The pro-
portion of ingredients in this concentrate mixture was as follows:
peanut meal, 45 percent crude protein, 106; wheat bran, 200;
ground oats, 200; hominy feed, 400; salt, 9; and steamed bone-
meal, 9 pounds. There were periods in the experiment when
some cows were fed lesser amounts of lower protein concentrates.
In the latter case, the number of cows and the duration of the
feeding period were about the same on irrigated and unirrigated
pastures.
Samples of clover and pangolagrass forage comparable to the
plant portions consumed by the cows were taken periodically in
1952 and 1953. Moisture and crude protein (N x 6.25) analyses
were made on these samples by methods described by the Associ-
ation of Official Agricultural Chemists (2).
EXPERIMENTAL RESULTS
The land used was well adapted for both whiteclover and pan-
golagrass. From the beginning of each grazing season through
May whiteclover was the principal forage, with pangolagrass
furnishing very little feed. When whiteclover growth declined
in May, pangolagrass spread to cover the ground and then began
a dense, upward growth. About the first of June pangolagrass
became the predominant forage, and whiteclover was contrib-
uting insignificant amounts of forage by the middle to latter
part of the month. Since the two periods of forage predominance
were well defined, from the beginning of grazing through May 31
is referred to as the clover-grazing season and from June 1 to
the termination of grazing as the grass season.
Rainfall and Irrigation Water Applied.-After the irrigation
equipment was installed on April 17, 1952, 7.2 inches of water
were applied to the irrigated plots to supplement the 3.6 inches
of rain that fell during the remainder of the clover season.
TUN I~5~
TDN 1955
LBS.
400
200 o I .
- IRRIGATED PASTURE
----- UNIRRIGATED PASTURE
-- BASE LINE
I RAINFALL
Fig. 2.-Total digestible nutrients obtained biweekly per acre from irrigated and unirrigated whiteclover-pangolagrass
pasture. Rainfall is shown by three-day periods.
RAINFALL,
IN.
4
2
Irrigation of Whiteclover-Pangolagrass Pasture
During the following grass season rainfall was 9.3 inches below
the 1903-1954 average for this period and a total of 13.7 inches
of water was applied to the irrigated pasture in 12 additions.
Subnormal precipitation continued during the 1953 clover grow-
ing season prior to initiation of grazing. Fourteen applications
totaling 7.9 inches of water were made during this period. Al-
though 11.6 inches of rain fell during the clover grazing season,
over one-half came during a 13-day interval and 9.6 inches of
water were applied to the irrigated plots during the other parts
of this grazing period.
Rainfall was heavy during much of the 1953 grass season, and
surface water frequently stood in low areas during August and.
September. Only 3.8 inches of water were applied during this
period. The 12.9 inches of rain that fell during the 1954 clover
season prior to grazing were adequate to maintain a satisfactory
soil moisture level.
Subnormal rainfall of 6.3 inches during the clover grazing
season was supplemented with 5.2 inches of irrigation water.
Rainfall during the 1954 grass season was low and 7.2 inches of
water were applied to the irrigated plots.
Although 12.7 inches of rain fell during the 1955 clover sea-
son prior to grazing, distribution was poor and four irrigations
were made during this period. Only 3.9 inches of rain fell dur-
ing the clover grazing period and 23.7 inches of water was ap-
plied to irrigated pasture. A summary of rainfall and supple-
mental water applied to the irrigated pasture during each grass
grazing season and clover season before grazing began and
during grazing is shown in Table 3. The distribution of rainfall
is illustrated in Figure 2.
Grazing Periods and Total Digestible Nutrients Obtained
per Acre.-The average initial grazing date of March 5 for the
irrigated pasture was 14.3 days earlier than that for the unirri-
gated plots. Grazing on both pastures was terminated by killing
frosts on October 29, 1952, and October 31, 1954. The forage
available was insufficient to justify pasturing the cattle after
November 23, 1953. Grazing on the irrigated pasture was con-
tinuous each year, but was interrupted by dry weather on the
unirrigated June 2-8, 1953, August 18-30, 1954, and April 27-
May 31, 1955.
Total digestible nutrients obtained from the pastures during
the clover grazing seasons were calculated by the inverse method
(1) to average 2,544 pounds for the irrigated and 1,743 pounds
TABLE 3.-SUMMARY OF RAINFALL AND SUPPLEMENTAL WATER APPLIED TO THE IRRIGATED PASTURE DURING EACH GRASS
GRAZING SEASON, FOR THE PERIODS BEFORE GRAZING WAS BEGUN ON CLOVER AND DURING EACH CLOVER GRAZING SEASON,
BY YEARS.
Periods
of Forage
Predominance *
Grass, 1952 ......
Clover, 1953 ....
Grass, 1953 .......
Clover, 1954 -
Grass, 1954 .......
Clover, 1955 -.
Irrigation Water
Applied
Before During
Grazing Grazing
Began** Season
Inches Inches
13.7
7.9 9.6
-- 3.8
5.2
-- 7.2
3.3 23.7
Number of
Irrigations
Before
Grazing
Began**
14.0
4.0
During
Grazing
Period
12.0
10.0
4.5
5.5
8.0
28.0
Rainfall
Before
Grazing
Began**
Inches
7.4
12.9
12.7
During
Grazing
Season
Inches
21.0
11.6
35.3
6.3
27.8
3.9
Mean Rainfall (1903-54)
for Periods *
Before During
Grazing Grazing
Began** Period
Inches Inches
30.2
11.3
9.6
12.0
9.2
31.7
9.4
30.3
8.4
Rainfall and irrigation data for clover periods are October 30, 1952 through May 31, 1953; November 24, 1953 through May 31, 1954; and
November 1 through May 31, 1955. The grass periods are June 1 through October 29, 1952; June 1 through November 23, 1953; and June 1 through
October 31, 1955.
** Clover grazing was begun March 3, 1953; March 2, 1954; and March 10, 1955.
Irrigation of Whiteclover-Pangolagrass Pasture
for the unirrigated. The production from June 1 until termina-
tion of grazing, when the pasture was comprised primarily of
pangolagrass, averaged 4,265 pounds for the irrigated plots and
3,899 for the unirrigated. The average increases by irrigation
of 801 pounds of total digestible nutrients per acre during the
clover season and 366 pounds during the grass season repre-
sented increases of 45.9 and 9.4 percent, respectively. The graz-
ing periods and total digestible nutrients obtained per acre from
irrigated and unirrigated pastures are shown for each grazing
season in Table 4.
TABLE 4.-GRAZING PERIODS ON AND TOTAL DIGESTIBLE NUTRIENTS PER
ACRE OBTAINED FROM IRRIGATED AND UNIRRIGATED PASTURES DURING CLOVER
AND GRASS SEASONS, BY YEARS.
Grazing Periods On
Irrigated
Pasture
6/1 -10/29
3/3 5/31
6/1 -11/23
3/2 5/31
6/1 -10/31
3/10- 5/31
Unirrigated
Pasture
6/1 -10/29
3/27- 5/31
6/1, -
6/9 -11/23
3/9 5/31
6/1 8/19
8/31-10/31
3/22- 4/26
TDN per Acre
Irri- Unirri- Increase
gated gated by Irri-
Pasture I Pasture gation
4,428 3,625 803
2,390 1,401 989
4,296 4,228 68
3,078 2,970 108
4,070 3,844 226
2,163 858 1,305
Distribution of the Feed Supply and Carrying Capacity of
the Pastures.-Distribution of the feed supply obtained from
the pastures was characterized by a relatively high yield during
the lush clover growth period in late March, April and early
May. Feed production then was lower following the decline in
clover growth and before pangolagrass covered the ground com-
pletely. A high level of production was attained again in late
June or early July. Earlier coverage and high production by
pangolagrass was stimulated by increasing the early May nitro-
gen application from 16 pounds per acre in 1952 to 32 pounds in
1953 and to 52 pounds in 1954. Productivity each year remained
at a high level during the summer and declined in the fall. The
total digestible nutrients obtained biweekly per acre from the
irrigated and unirrigated pastures and total rainfall by three-
Grazing
Seasons
1952 Grass ......
1953 Clover ......
1953 Grass ........
1954 Clover ......
1954 Grass ........
1955 Clover .....
Florida Agricultural Experiment Stations
day periods are shown by years in Figure 2. The base line repre-
sents a suggested uniform level of total digestible nutrients per
acre one may use in calculating the acreage of pasture needed.
Irrigation was begun April 18, 1952, and differences in pasture
due to irrigation were established by the beginning of the grass
season, at which time the comparative study was begun.
The distribution of feed obtained from the irrigated pasture
was more uniform each year than that from the unirrigated pas-
ture. Likewise, the fluctuations were less for the irrigated pas-
tures during successive years. Factors contributing to this im-
provement in uniformity of the feed supply were: applying sup-
plemental water, increasing the number of plots from two in
1952 to four in 1953 and 1954, employing the strip grazing tech-
nique in 1955 and making larger applications of nitrogen in
early May.
Since the nutritive requirement of a dairy herd is relatively
constant during the year, the uniformity of forage supply pro-
vided by a pasture is an important factor in determining the
acreage to grow, the amount of supplemental feed necessary and
the surplus feed that will accumulate during the grazing season.
The amount and distribution of total digestible nutrients ob-
tained from the pastures each year were studied in order to in-
terpolate a uniform level for the entire grazing season that may
be used as a basis for determining the needed acreage of pasture.
Under the growing conditions of 1952, where two plots were
used in each rotation and 142.5 pounds of nitrogen top-dressing
were applied per acre, 300 pounds of total digestible nutrients
biweekly per acre is suggested as a level to rely on from pastures
grown similarly. With four plots used in each rotation during
the subsequent two years, along with heavier annual applications
of nitrogen and with the strip grazing technique employed in
1955, a higher biweekly level of 336 pounds of total digestible
nutrients per acre is a suggested level to rely on from this type
pasture. These levels of total digestible nutrients are indicated
for each year by the base lines shown in Figure 2.
Using these biweekly levels of total digestible nutrients as a
basis for determining the pasture acreage needed and assuming
that 1,000-pound cows obtained total digestible nutrients from
pasture sufficient to support maintenance plus production of 12
pounds daily of milk testing 4 percent butterfat, 0.55 acre per
cow would be needed under the conditions of 1952 and 0.49 acre
during the subsequent years. If the standard cow day (16
Irrigation of Whiteclover-Pangolagrass Pasture 13
pounds of total digestible nutrients) is used as the unit daily
requirement per animal, 0.75 acre per cow would have been
needed under the conditions of 1952 and 0.67 acre for the other
years.
If the base lines in Figure 2 represent the uniform levels of
total digestible nutrients needed per acre of pasture, then an
annual average of 5,240 pounds would have been grazed from
the irrigated pastures and an average of 1,509 pounds would
have occurred in surplus forage. On the unirrigated pasture an
average of 4,216 pounds of total digestible nutrients would have
been grazed and 1,426 pounds would have occurred in surplus
forage. Since the distribution of feed from the irrigated pasture
was more uniform, an annual average of 1,024 pounds more total
digestible nutrients would have been grazed per acre, while
only 143 pounds more of total digestible nutrients per acre would
have occurred in surplus forage.
The level of total digestible nutrients supplied by the pas-
tures generally was above that of the base lines in Figure 2 from
June 1 through October 14, 1952, and from the initiation of
grazing through September 29, 1953, October 1, 1954, and May
31, 1955. During the intervals between these dates the level
of total digestible nutrients obtained from the irrigated pastures
fell below the base line, an average of 42 days per grazing sea-
son, and the pasture was deficient an average of only 284 pounds
of total digestible nutrients. The total digestible nutrient level
from the unirrigated pasture was below the base lines an aver-
age of 86 days per grazing season and there was an average de-
ficiency of 1,299 pounds of total digestible nutrients. Thus, con-
siderably more supplemental feeding would have been required
under the unirrigated pasture program.
Composition of Forage Samples.-Portions of whiteclover
plants and pangolagrass shoots comparable to those consumed
by the cows were taken for analyses from the irrigated and un-
irrigated plots in the summer of 1952 and at about monthly in-
tervals from March to September, 1953. The intervals of time
following fertilization and stage of maturity were about the
same for samples taken from the irrigated and unirrigated pas-
tures. Dates samples were taken, their dry matter and crude
protein content and a description of the forage samples are shown
in Table 5.
The dry matter and crude protein content of the whiteclover
samples were comparable to those reported by Morrison (9).
TABLE 5.-CHEMICAL COMPOSITION OF WHITECLOVER AND PANGOLAGRASS FORAGE SAMPLES FROM
IRRIGATED AND UNIRRIGATED PASTURES.
Type of
Forage
Whiteclover ...
Whiteclover ....
Whiteclover* ..
Whiteclover* '
Pangolagrass
Pangolagrass
Pangolagrass
Pangolagrass
Pangolagrass
Pangolagrass ._
Pangolagrass*
Pangolagrass*
Pasture
Irrigated
Unirrigated
Irrigated
Unirrigated
Irrigated
Unirrigated
Irrigated
Unirrigated
Irrigated
Unirrigated
Irrigated
Unirrigated
Date
Sampled
3/29/53
3/31/53
5/12/53
5/12/53
7/ 3/53
7/ 7/53
8/ 9/53
8/11/53
8/27/53
9/ 3/53
8/22/52
8/22/52
Dry
Matter
%
15.7
16.1
20.7
22.4
16.5
16.5
15.8
17.3
13.7**
15.4
16.9
18.8
* Forage samples taken during dry periods.
** Forage sample damp when collected and values therefore are low.
Crude Protein
Fresh
Forage
%
4.2
4.3
5.1
5.0
3.1
2.9
2.7
2.8
2.4**
2.8
3.6
2.8
Dry
Forage
%
26.6
27.0
24.5
22.1
18.7
17.7
16.9
16.0
17.6
18.3
21.4
15.1
Forage
Sample
Description
Clover 9 in. Tall
Clover 7 in. Tall
Clover 7 in. Tall
Clover 6 in. Tall
Shoots av. 5 in.
Shoots av. 5 in.
Shoots av. 6 in.
Shoots av. 6 in.
Shoots av. 5 in.
Shoots av. 5 in.
Shoots av. 412 in.
Shoots av. 4 in.
Irrigation of Whiteclover-Pangolagrass Pasture
Dry matter content was low and crude protein on the dry basis
was high for samples taken from both irrigated and unirrigated
pastures during the lush growth period of March. The more
mature clover, containing some dry seedheads and dry leaves,
sampled in May was higher in dry matter but lower in crude
protein content on the dry basis. The unirrigated sward was
wilted and contained a larger proportion of brown forage as a
result of soil moisture deficiency. Thus, the dry matter content
was higher and the crude protein lower than that for the irri-
gated pasture sample.
Pangolagrass samples taken in 1953 were succulent and rel-
atively high in crude protein content. Rainfall was heavy dur-
ing the season and soil moisture usually was adequate for growth.
Therefore, there was little difference in composition of samples
from unirrigated and irrigated plots. During a moisture de-
ficient period in 1952 pangolagrass grown on unirrigated plots
had shorter internodes. The dry matter content of 18.8 percent
was higher and crude protein content of 15.1 percent on the dry
matter basis was lower than for the sample from the irrigated
plot. The higher crude protein content of the 1952 sample from
irrigated pasture is due partly to the short average length of
shoots which resulted in a higher proportion of foliar parts.
Milk Production, Body Weight Changes and Percent of Re-
quired Total Digestible Nutrients Obtained from Pasture.-The
level of milk production of the Jersey and Guernsey cows grazing
the irrigated pasture was similar to that of those grazing the
unirrigated pasture. Daily production for the three-year period
of those grazing the irrigated pasture averaged 31.6 pounds of
milk testing 4.8 percent butterfat, while the average for those
grazing unirrigated pasture was 30.3 pounds with an average
test of 4.9 percent. Expressed as 4 percent fat-corrected milk,
average daily production was 35.3 pounds for those grazing the
irrigated pasture and 34.4 for those on the unirrigated pasture.
Cows grazing the irrigated pastures over the three-year
period had an average initial weight of 855 pounds, which was
close to the 847 pounds for those on the unirrigated pasture.
Small average losses in body weight for the cows on each type
of pasture occurred during the grass season in 1952 and 1953,
but animals grazing each pasture made small gains in 1954 and
during the clover season of 1955. These small variations in
body weight reflect changes in average quality forage for the
different years. Whiteclover, which is of higher quality than
Florida Agricultural Experiment Stations
pangolagrass, was the principal forage consumed in 1955. Clover
furnished about 43 percent of the total digestible nutrients ob-
tained from all pastures in 1954, as compared with 25 percent
for the unirrigated and 36 percent for the irrigated pastures in
1953. Likewise, the quality of pangolagrass was higher in 1954
as compared with earlier years, due to heavier nitrogen fertili-
zation and improvements in grazing management practices. Re-
sults of the experiment are summarized in Table 6.
The cows on irrigated pasture averaged 10.6 pounds of total
digestible nutrients daily and those on the unirrigated plots de-
rived an average of 10.8 pounds of total digestible nutrients daily
from the pasture. Feed obtained from pasture furnished 60
percent of their total digestible nutrient intake. The remaining
portion of their total digestible nutrient requirements was pro-
vided by a concentrate allowance averaging 9.4 pounds daily per
cow for those on irrigated pasture and 9.1 pounds for those on
the unirrigated plots.
Hay Equivalents Obtained from the Pastures.-A practical
and common method of expressing the worth of pastures is in
terms of equivalent amounts of hay or hays that would be re-
quired to replace it. Since whiteclover is similar in quality and
composition to alfalfa, this hay (containing 50.3 percent of total
digestible nutrients) was used as the reference roughage in eval-
uating the pastures during the clover grazing seasons. The
composition of pangolagrass samples indicated that its quality
was superior to that of grasses reported by Morrison (9); so
mixed hay, less than 30 percent legumes (49.8 percent total di-
gestible nutrients), was used as the reference forage in evaluat-
ing pastures during the grass seasons. The feed obtained from
the pastures during the clover grazing season was equivalent to
an average of 2.53 tons per acre for the irrigated and 1.73 tons
for the unirrigated. During the pangolagrass grazing season
the mixed hay equivalent value per acre of the irrigated pasture
averaged 4.28 tons and the unirrigated averaged 3.91 tons. The
total annual hay equivalent per acre averaged 6.81 for the irri-
gated pasture and 5.64 tons for the unirrigated.
Calculated Production Costs and Feed Replacement Values.-
The net return that may be realized by the utilization of a pas-
ture in a feeding program is fundamental in determining the de-
sirability of its usage. Likewise, the increase in value that may
be anticipated by irrigating a given pasture is important in re-
solving the advisability of adopting this practice.
Irrigation of Whiteclover-Pangolagrass Pasture
Production costs of the unirrigated pastures and nonirriga-
tion costs of the irrigated pastures were determined by using
prevailing market prices for fertilizer and land rent. Assess-
ments for cultural practices were based on charges for local
custom work when pastures were 10 acres or larger. Land rent
was $8. The cost of $15 per acre for sprigging grass and seed-
ing clover was amortized over a 10-year period. Fertilizer costs
per ton were: ammonium nitrate, $85; 20 percent superphos-
phate, $24.33; 18 percent superphosphate, $21.90; muriate of
potash (60 percent KO2), $54; and ground limestone, applied,
$4.90. Assessments for cultural practices per acre were: ap-
plying superphosphate, $1.50; spreading muriate of potash,
$1.35; top-dressing with nitrogen, $1.35; scattering droppings,
$1.25; mowing, $1.35; mowing and scattering droppings, com-
bined, $1.45; and raking grass, $1.35. The above production
Fig. 3.-The experimental whiteclover-pangolagrass pastures (unirrigated
on left, irrigated on right) during dry weather in May 1955.
TABLE 6.-VALUE OF IRRIGATED AND UNIRRIGATED PANGOLAGRASS-WHITECLOVER PASTURES GRAZED BY LACTATING COWS, BY
YEARS AND AN AVERAGE FOR THE THREE YEARS.
Av. initial weight of cows, lb. ......-...........
Av. change in body weight per cow, Ib......
Av. daily milk production per cow, lb. -........
Av. daily production 4 percent F.C.M.,
per cow lb......... .... -- .. .... .........
Alfalfa hay equivalent of forage predomin:
clover, per acre, tons .........................
Mixed grass-clover hay equivalent of forage
dominately grass, per acre, tons ..-.......
Av. daily concentrate consumption per cow,
Calculated feed replacement value of fora1
per acre ................. ...... .. ...
Calculated cost of pasture production
excluding irrigation, per acre ................
Feed replacement value increase per acre ir
of water applied for clover ......... -
Feed replacement value increase per acre ir
of water applied for grass .....................
Irrigated Pasture Av.
Year ) For
--- --Three
1952* 1953 1954 1955** Years
I846 817 887 894 855
--19 --22 +17 +20 -4
29.7 31.0 31.6 33.0 31.6
.. 34.6 34.6 35.3 39.4 35.3
lately I
......... e -- 2.38 3.06 2.15 2.5i
pre- 1
S 4.44 4.31 4.09 -4.21
b..... 10.1 8.8 9.4 9.8 9.4
ge, I I
-..- $150.00 $273.00 $292.00 $107.00 $274.0(
$ 52.00 $ 82.00 $ 85.00 $ 23.00 $ 81.0(
Lch
-. $ 2.73 $ 2.17$ 2.26$ 2.4i
ich I
..-..-. $ 1.66 $ 1.27 $ 1.52 $ 1.5(
.
Unirrigated Past
Year
1952* 1953 1954
ure Av.
For
Three
1955* Years
856 847
+22 -5
36.1 30.3
42.7 34.4
1 0.85 1.73
o.uu --
9.7 13.0
39.00j$ 44.00
3.91
9.1
$220.00
21.00($ 80.00
* Values are for portion of year from June 1 through October 29, 1952.
** Values are for portion of year from November 1, 1954 through May 31, 1955.
Irrigation of Whiteclover-Pangolagrass Pasture
costs (excluding irrigation) per acre averaged $81.00 per year
for the irrigated pasture and $80.00 for the unirrigated (Table 6).
In calculating the feed replacement value of the pastures, dif-
ferences in quality and value of the clover and pangolagrass were
considered. Likewise, the roughage requirement of a herd is
rather constant and some surplus forage, which is less valuable,
accumulates during the lush growth period under a practical
permanent pasture program. Therefore, the total digestible
nutrient levels indicated by the base lines in Figure 2 were con-
sidered to represent the amounts that could be utilized for graz-
ing purpose in a practical program and the production above the
base lines was considered as surplus. The alfalfa hay equivalent
of the clover forage that could be grazed was valued at $54 per
ton, while the hay equivalent of the surplus forage was valued
at $27 per ton. The mixed hay equivalent of pangolagrass uti-
lized as grazed forage was valued at $40.50 per ton, while the
surplus was considered to be worth $20.50 per ton.
The annual feed replacement value of the unirrigated pasture
averaged $220.00 per acre with a net return of $140.00 per acre.
The average annual application of 24.8 inches of water to the
irrigated pasture was accompanied by an average increase in
returns above other production costs of $53.00 per acre, or
$2.13 per inch of water applied. The increase in return above
other production costs for the 16.6 inches of water applied dur-
ing the clover season was $2.43 per inch and for the 8.2 inches
applied during the grass season was $1.56 per inch (Table 6).
DISCUSSION
Costs of owning and operating the system employed to irri-
gate the small experimental plots were not comparable to those
for larger commercial irrigation systems. A brief general dis-
cussion of pasture irrigation methods and costs is presented to
assist in appraising this practice.
Two methods of irrigating pastures in Florida are classified
as sprinkler and sub-irrigation. With the sprinkler system water
is distributed on the soil by rotary sprinklers, perforated pipe
and certain types of rotary and stationary nozzles. Sub-irriga-
tion systems are made up of a series of main or lateral ditches
or drains and generally are used for drainage as well as irriga-
tion. Discharge pressures for sprinkler systems range between
15 and 100 pounds per square inch, while free discharge is stand-
ard for sub-irrigation systems.
Florida Agricultural Experiment Stations
Economic studies have shown that costs of owning and oper-
ating irrigation systems vary widely and are influenced by loca-
tion, management, water source and type of system. Initial in-
vestment in the system usually is lower for sub-irrigation, rang-
ing from about $30 to $80 per acre as compared to $70 to $150
per acre for sprinkler installations. Irrigation cost figures com-
monly used in Florida range from $0.25 to $0.75 per acre-inch
of water applied on pasture by the sub-irrigation method and
$2.00 to $3.50 per acre inch applied by the sprinkler system.
In this experiment whiteclover and pangolagrass were grown
on a high-quality flatwoods soil (Scranton loamy fine sand) well
adapted for the production of both. Liberal fertilization prac-
tices were followed and the grazing management program was
intensive. Under these conditions the increase in yield of total
digestible nutrients averaged 48.3 pounds per acre-inch of water
applied for clover and 44.1 pounds for that applied to pangola-
grass. Increases in total digestible nutrient yields per acre-
inch of irrigation water applied to pastures reported by other in-
vestigators were 69.2 pounds (4), 72.4 pounds (16) and 79.9
pounds (10). In these experiments the clover stand declined in
the unirrigated pasture and in two cases (4, 16) only a few
plants survived until the end of the experiment. Retention of
a good whiteclover stand during this experiment helped to main-
tain a high production level in the unirrigated pasture and this
tended to minimize the increases in total digestible nutrient
yields resulting from application of water to the irrigated plot.
The increase in calculated net returns from irrigation aver-
aged $2.13 per acre-inch of water applied. According to the
cost range figures of $2.00 to $3.50 per acre-inch of water ap-
plied by sprinkler systems, this average net return would be
marginal for the most efficient operations. If a comparable net
return per acre-inch of water applied can be obtained using sub-
irrigation, this practice would prove economical where land is
suitable for this type of irrigation. Soils that are rather level
and that have a permeable stratum above a rather impervious
layer or soils with a high water table are suitable for sub-irriga-
tion where a supply of water requiring low lift is available.
The increase in net returns of $2.43 per acre-inch for the
annual average of 16.6 inches of water applied for clover produc-
tion was considerably higher than the $1.56 per acre-inch realized
for the seasonal average of 8.2 inches applied for pangolagrass.
The higher return from clover was due to earlier grazing and
Irrigation of Whiteclover-Pangolagrass Pasture
a more uniform distribution of feed supply from the irrigated
pasture, more increase in total digestible nutrients per acre-inch
of water applied and the higher quality (value) of the clover
forage.
SUMMARY AND CONCLUSIONS
Irrigated and unirrigated whiteclover-pangolagrass pastures
grown on Scranton loamy fine sand and fertilized liberally were
grazed intensively with separate groups of lactating cows for a
three-year period. Annual rainfall averaged 46.3 inches and an
annual average of 24.8 inches of water was applied to the irri-
gated plots with an overhead sprinkler system.
From the beginning of grazing each year through May,
clover was the principal forage, and after the first of June pango-
lagrass furnished practically all of the forage. Total digestible
nutrients obtained from the pasture during clover grazing sea-
son averaged 2,544 pounds for the irrigated and 1,743 pounds
for the unirrigated pasture. Production of total digestible nu-
trients from June 1 until termination of grazing, when pangola-
grass was the primary forage, averaged 4,265 and 3,899 pounds
for the respective pastures. There was an increase of 48.3
pounds of total digestible nutrients per acre-inch of water ap-
plied for clover and 44.1 pounds per acre-inch for that applied
during the grass season.
Grazing began an average of 14.3 days earlier (March 5) on
the irrigated pastures, but termination dates were the same
on both. Cattle grazed the irrigated pasture continuously each
year, but grazing was interrupted on the unirrigated once an-
nually for an average period of 18.3 days.
Calculated production cost of the unirrigated pasture aver-
aged $80 per acre, or 1.41 cents per pound of total digestible
nutrients produced, and net returns averaged $140 per acre.
The average application of 24.8 inches of water to the irrigated
pasture was accompanied by an increase in returns above other
production costs of $53 per acre over that of the unirrigated, or
$2.13 for each acre-inch of water applied. The increase in re-
turns above other production costs was $2.43 per acre-inch for
the 16.6 inches of water applied for clover and $1.56 for the
8.2 inches applied during the grass season. These data indicate
that under conditions favorable for the production of white-
clover or similar high-quality forages, returns per unit of irriga-
tion water applied to them should be higher than for that used
on pangola or similar permanent pasture grasses.
Florida Agricultural Experiment Stations
The Scranton loamy fine sand soil on which the experiment
was conducted had a high water table which provided some res-
ervoir to the pasture. Similar results may be anticipated under
comparable conditions on soils with similar water table and
water-holding capacity.
Total irrigation cost figures commonly used in Florida range
from $2 to $3.50 per acre-inch of water applied to pasture by
sprinkler systems and $0.25 to $0.75 per acre-inch applied by
sub-irrigation systems. According to these figures, the increase
in average net returns from irrigation of whiteclover-pangola-
grass pasture under the conditions of this experiment would be
marginal for the most efficient sprinkler type operations. If a
comparable increase in net returns per acre-inch of water ap-
plied were obtained by sub-irrigation, the practice would be
economical on land suitable for sub-irrigation.
ACKNOWLEDGMENTS
Appreciation is expressed to H. L. Somers and A. B. Sanchez
for assistance in supervising the management of cattle and pas-
tures, and to T. A. Monday for his assistance in operating the
irrigation system during the experiment.
LITERATURE CITED
1. Amer. Soc. Agron., Amer. Dairy Sci. Assoc., Amer. Soc. Anim. Prod.,
and Amer. Soc. Range Mgmt. Joint Committee. Pasture and range
research techniques. Agron. Jour. 44: 39-50. 1952.
2. Association of Official Agricultural Chemists. Official and tentative
methods of analysis. 7th ed. 1950.
3. CARRECKER, J. R., W. J. LIDDELL and H. B. HENDERSON. Supplemental
irrigation of pastures in the Southeast. Proc. 22nd Ann. Meet.
Sou. Div., Amer. Dairy Sci. Assoc.: 20-21. 1949.
4. EWING, J. A. Irrigated pasture for dairy cows. Tenn. Agr. Exp. Sta.
Bul. 216. 1950.
5. HAZELWOOD, B. P. All-year pasturing with and without concentrates
for dairy cattle. Tenn. Agr. Exp. Sta. Cir. 58: 1-4. 1936.
6. JONES, B. A., JR., and H. L. WAKELAND. Supplemental irrigation of
pastures. Agr. Eng. 36: 181-84. 1955.
7. JONES, D. W., E. M. HODGES and W. G. KIRK. Irrigation of clover-
grass pastures. Proc. Assoc. Sou. Agr. Workers 50th Ann. Con-
vention: 200. 1953.
8. MITCHELL, W. G. "Ribbon Grazing" brings more milk. Prog. Farmer.
Ga.-Ala.-Fla. Ed. 70(9): 28. 1955.
Florida Agricultural Experiment Stations
The Scranton loamy fine sand soil on which the experiment
was conducted had a high water table which provided some res-
ervoir to the pasture. Similar results may be anticipated under
comparable conditions on soils with similar water table and
water-holding capacity.
Total irrigation cost figures commonly used in Florida range
from $2 to $3.50 per acre-inch of water applied to pasture by
sprinkler systems and $0.25 to $0.75 per acre-inch applied by
sub-irrigation systems. According to these figures, the increase
in average net returns from irrigation of whiteclover-pangola-
grass pasture under the conditions of this experiment would be
marginal for the most efficient sprinkler type operations. If a
comparable increase in net returns per acre-inch of water ap-
plied were obtained by sub-irrigation, the practice would be
economical on land suitable for sub-irrigation.
ACKNOWLEDGMENTS
Appreciation is expressed to H. L. Somers and A. B. Sanchez
for assistance in supervising the management of cattle and pas-
tures, and to T. A. Monday for his assistance in operating the
irrigation system during the experiment.
LITERATURE CITED
1. Amer. Soc. Agron., Amer. Dairy Sci. Assoc., Amer. Soc. Anim. Prod.,
and Amer. Soc. Range Mgmt. Joint Committee. Pasture and range
research techniques. Agron. Jour. 44: 39-50. 1952.
2. Association of Official Agricultural Chemists. Official and tentative
methods of analysis. 7th ed. 1950.
3. CARRECKER, J. R., W. J. LIDDELL and H. B. HENDERSON. Supplemental
irrigation of pastures in the Southeast. Proc. 22nd Ann. Meet.
Sou. Div., Amer. Dairy Sci. Assoc.: 20-21. 1949.
4. EWING, J. A. Irrigated pasture for dairy cows. Tenn. Agr. Exp. Sta.
Bul. 216. 1950.
5. HAZELWOOD, B. P. All-year pasturing with and without concentrates
for dairy cattle. Tenn. Agr. Exp. Sta. Cir. 58: 1-4. 1936.
6. JONES, B. A., JR., and H. L. WAKELAND. Supplemental irrigation of
pastures. Agr. Eng. 36: 181-84. 1955.
7. JONES, D. W., E. M. HODGES and W. G. KIRK. Irrigation of clover-
grass pastures. Proc. Assoc. Sou. Agr. Workers 50th Ann. Con-
vention: 200. 1953.
8. MITCHELL, W. G. "Ribbon Grazing" brings more milk. Prog. Farmer.
Ga.-Ala.-Fla. Ed. 70(9): 28. 1955.
Irrigation of Whiteclover-Pangolagrass Pasture
9. MORRISON, F. B. Feeds and Feeding. 22nd ed. The Morrison Pub-
lishing Co. 1956.
10. MURLEY, W. R., and R. K. WAUGH. Half Again. N. C. Agr. Exp.
Sta. Res. and Farming. 11(1): 8-9. 1952.
11. REAVES, C. W. Contributions of Florida dairy farms to the feed sup-
plies of some selected milking herds. M. S. Thesis, University of
Florida. 1956.
12. ROBERTS, N. K., and E. D. SMITH. Unpublished data. Fla. Agr. Exp.
Sta.
13. TEMPLETON, W. C., JR., C. F. BUCK, P. G. WOOLFOLK, E. N. FERGUS,
P. E. KARRAKER, and E. G. WELCH. Some effects of irrigation and
fertilization of a Kentucky bluegrass-whiteclover pasture. Proc.
Assoc. Sou. Agr. Workers 52nd Ann. Convention: 192. 1955.
14. USDA Agr. Res. Ser. Dairy-herd-improvement-association letter. ARS-
52-20. 31(9). 1955.
15. USDA Bur. Agr. Econ., Orlando, Fla. Cooperating with Fla. Dept. of
Agr., Dairy Div. Milk production and feed reports. 1951-56.
16. VAN HORN, A. G., W. M. WHITAKER, R. H. LUSH, and J. R. CARREKER.
Irrigation of pastures for dairy cows. Tenn. Agr. Exp. Sta. Bul.
248. 1956.
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