foo
Crop Yield Comparisons and Economic Analysis
for
Single- and Double-crop Systems
I.D. Teare, D.L. Wright,
R.D. Barnett, D.W. Gorbet, T.D. Hewitt
Central Science
Library
FEB 13 1990
University of Florida
North Florida Research and Education Center, Quincy, FL 32351 and
Marianna FL 32446 (Institute of Food and Agricultural Sciences,
Univ. of Fla., Gainesville, FL 32611). Research Report NF-90-6.
Introduction
North Florida has been traditional an area of agronomic crop
production. While there have been short cycles in acreage
devoted to other specific crops, the majority of the acreage has
remained agronomic.
The low-energy-thrust program of the '70's speeded the
development of the no-till or minimum-till planting equipment and
technology that has been instrumental in reducing land prepara-
tion costs and increasing cash returns of both single- and
double-crop systems.
The most successful agronomic double-crop system in the
southeast has been fall planted wheat (primary-crop), harvested
between 24 May and 1 June, followed by a soybean crop (double-
crop) planted -around 12 June (Herzog et al., 1989, and Wright,
1984). There are presently two major problems associated with
the production and sale of soybean. The first is the low world
price of soybean. Soybean .prices for the last six years have
been: 1984\$6.20, 1985\$5.20, 1986\$4.90, 1987\$5.55, 1988\$7.50,
and 1989\(estimated)$6.00 (based on USDA Fla. Agric. Statistics
Service, Field Crops, 1222 Woodward Street, Orlando, FL 32803).
The. second is that nematodes numbers build-up under a soybean
crop (Whitty, 1988), not only affecting the soybean yield, but
the yield of following crops that are susceptible to nematodes
(especially root knot).
Nematode problems can be moderated using rotation crops with
low host suitability. Two crops with low host suitability for
nematodes are corn and sorghum, although host suitability varies
2
in relation to hybrid. Therefore a corn or sorghum crop in
rotation with a susceptible crop lowers the nematode numbers
available to feed upon the subsequent susceptible crops.
Sorghum has shown varying potential in double-cropping
(Sanford et al., 1986), but in Florida the use of sorghum as a
double-crop in relation to a primary-crop has not been reported.
The objective of this work was to compile information about
specific yields of crops that could be used with wheat in a
double-crop system or compared with other competitive single- or
double-crop systems in North Florida.
Materials and Methods
The research was conducted at the North Florida Research and
Education Center at Quincy, FL on a Norfolk sandy loam soil
(fine-loamy, -siliceous, thermic, Typic Paleudult) and/or
Marianna, FL on a Chipola loamy sand (loamy, siliceous, thermic
Arenic Paleudult).
The experimental design for all crops was a randomized
complete block with four replications.
WHEAT: Florida 302 and 303 were planted from 25 Nov to 10 Dec
from 1985 to 1988 at a planting rate of 1.5 to 2 bu/A. The
initial fertilization occurred one day prior to planting when 500
lb of 5-10-15 (N-P-K) was applied to the seedbed. Urea (46-0-0)
was applied according to fertilizer test from 22 Jan to 7 Feb
each year at approx. 50 lb N/A. All K was applied preplant.
Weeds were controlled according to species and number present in
relation to standard extension recommendations. Wheat yields
were corrected to 12% moisture.
SOYBEAN: Braxton soybean were planted 12 June in 6-row plots x
20-m with 0.76-m row spacing. Yield estimates were made by
harvesting 12-m of row from 2 rows. Plots were sprayed about 29
Sept with Asana 1.9 EC at 0.025 lb(AI)/A each year to control
stink bugs and about 1 Sept with Dimalin 25W at 0.5 oz (AI)/A
each year to control velvet bean caterpillar. Spray applications
were made at 36 psi and with 25 gal water/A. Soybean were not
fertilized. Soybean yields were corrected to 13% moisture.
CORN: Tropical corn: Pioneer hybrid brand X-304C (coded X304C)
was planted in 4-row plots in a moderate-energy-input system
defined as: 1. nitrogen fertilization at 120 lb N/A (20 lb/A
applied on the surface at planting and 100 lb/A side dressed when
the crop was 24 inches high in 1985 and changed to 12 inches high
for 1986, 1987-, 1988; and 2. no irrigation. X304C was planted
with a no-till planter in 24 foot rows with 30-inch spacing
between rows at a population density of 18,000 plants/A.
Tropical corn yields were corrected to 15.5% moisture.
Temperate corn: Asgrow hybrid brand 5509 (coded A5509) was
planted in 4-row plots in a moderate-energy-input system
(described above) in 1988 to compare with the high-energy-input
system recommended in the Southeast and known as the plow-layer-
management system defined as; 1. Fertilizer applied for maximum
corn yields according to soil test results up to the rates of
300-100-300 lb/A of N-P-K; 2. irrigation as scheduled by
tensiometers placed at 6 inch depth reached 0.02 MPa. A5509 was
planted with a no-till planter in a prepared seedbed in 24 foot
rows with 30-inch spacing between rows at a population density of
30,000 plants/A. Grain yields were harvested by plot combine
from 2 row trimmed to 20 feet. Two hundred and sixty lb N/A was
applied at fixed amounts according to the following schedule:
1. prior to planting, 50 lb N/A was applied as 1,000 lb 5-10-15;
2. at planting 10 lb N/A was applied on the surface as ammonium
polyphosphate (10-34-0); 3. About 21 April when the corn was
24 inches tall, 120 Ib N/A was banded near the row; 4. on 13
May 100 lb N/A was injected through the overhead sprinkler with
boron. Total N applied was 280 lb N/A. Temperate corn yields
were corrected to 15.5% moisture.
SORGHUM: Planting date, hybrid, and previous crop is shown for
sorghum in table 4. Nitrogen was applied at 100 lb/A about 20
days after planting. Four row plots were 48 feet long with rows
30 inches apart. Sorghum was planted with a no-till planter and
subsoiler (set at 12 inch depth). Plant density was approxi-
.mately 45,000 sorghum plants/A. Grain yield was determined on 10
foot sections of center row. Late planted sorghum required irri-
gation which was scheduled as in corn. Late planted sorghum also
had bird problems. Bird feeders with corn soaked in Avinol and
broadcast sprayed Azodrin 5 (2 pt/A) were used for control with
varing degrees of success. Midge was a problem in sorghum in
1982 and was broadcast sprayed 21 July with a hiboy sprayer with
Sevin at 3 lb/A. Midge and webworm were problems in late Aug,
1983 but both were controlled with Lannate at 2 pt/A or Orthene
at 1 3/4 pt/A. Fall armyworm can also be a problem on sorghum
but did not reach economic threshholds requiring treatment during
the study. Weeds were controlled as necessary according to
5
extension recommendations. Sorghum yields were corrected to 12%
moisture.
Results and Discussion
Wheat in North Florida in the past was used as a winter
grazing crop, but as cattle numbers dwindled in the 70's, wheat
acreage also dwindled to 17,000 acres in 1978. In 1979, the
Florida reporting service ceased reporting wheat acreage planted
or wheat yields for the state of Florida. With the release of
Florida 301 in 1980, wheat acreages increased to a high of
160,000 acres in 1985 and has averaged about 100,000 each year
since. By 1984, Florida 301 was grown on more than 1 million
acres, making it the most popular soft red wheat winter wheat in
the South. Florida 302 was released in 1984 and has become the
most popular wheat grown from East Texas To Virginia and Pennsyl-
vania. In 1988, nearly 3 million acres of Florida 302 were
grown. As successful as Florida 302 is, it has a problem in the
double-crop system, since it matures about 1 June or 10 days
to 1 week later than Florida 301. At present Florida 302 is the
predominant wheat cultivar grown in the southeast in double-crop
systems. However a new cultivar, Florida 303 was selected and
released in 1988 for its desirable trait of high yield coupled
with early maturity (reaching maturity about 12 to 16 May) and
resistance to leaf rust and powdery mildew (Barnett, et al.,
1988). This makes it a more ideal wheat cultivar for use in a
double-cropping system because earlier maturity provides a wider
window for the early planting of soybean, tropical corn, or
sorghum (using 15 June as the cut-off date, after which the fall
6
armyworm can cause devastating outbreaks on tropical corn).
Wheat yields are shown in Table 1.
Table 1. Wheat Yields1 (bu/A) for Florida 301, 302, and 303
during 1985 to 1988 at Quincy FL.
Year Florida 301 Florida 302 Florida 303
bu/A
1985 56 45 49
1986 60 48 60
19872 57 55 64
19873 43 65 62
19884 65 63 70
19885 58 62 70
Mean 56 56 62
1 Agronomists of IFAS, Univ. of Fla., Florida Field and Forage
Crop Variety Reports: AY86-10, AY87-2, AY88-02, AY89-07.
2 State Variety Test
Uniform Southern Test
4 Early Planted State Test (12-1-87)
s Late Planted State Test (12-9-87)
Soybean is an ideal low-energy-input crop for double-cropping
after wheat in the south. Florida 302 wheat is harvested from 24
May to 10 June each year in North Florida. Soybean growing re-
quirements fit the environment at that time. Herzog (1988) has
shown that Braxton yields the best when planted 8 June. Soybean
has very few disease pests, but many insect pests, ie., velvet-
bean caterpillar, soybean looper, and stink bug. Therefore,
soybean fields must be scouted on a regular basis during the
growing season to monitor pests and determine when spray applica-
tion is necessary. Soybean yields in relation years and early
June planting date are shown in Table 2.
Table 2. Soybean (Braxton) yields' [early planted (15 May),
without nematodes] in relation to years, 1983 through 1988.
Year Mean
Yield
(bu/A)
1983 42
1984 42
1985 35
1986 41
1987 55
1988 42
Mean 43
1 Agronomists of IFAS, Univ. of Fla., Florida Field and Forage
Crop Variety Reports: AY84-9, AY85-10, AY86-10, AY87-2,
AY88-01, AY89-07.
Table 3. Nematodes in relation to Braxton soybean yieldl for
specific locations2 during 1981 to 1988.
Peanut
root-knot
Meliodogyne
arenaria
Javanese Soybean cyst Soybean cyst Southern
root-knot race 3 race 4 root-knot
Meliodogyne Heterodera Heterodera Meliodgyne
javanica glycines glycines incognita
bu/A (Location)
34 Jay
29 Jay
27 SA
5 SA
16 SA
16 SA
6 Jay
5 Jay
9 Jay
5 LO
19 LO
12 LO
2 LO
7 LO
32 Jay
30 Jay
30 Jay
24 Jay
19 JC
20 Jay
7 JC
45 Jay
42 Jay
42 Jay
27 Jay
38 Jay
24 Jay
21 Jay
17 MC
20 MC
26 Jay
32 Jay
1 Agronomists of IFAS, Univ. of Fla., Florida Field and Forage
Crop Variety Reports: AY82-7, AY83-13, AY84-9, AY85-10,
AY86-10, AY87-2, AY88-02.
2 LO=Live Oak, SA=Santa Rosa, JC=Jackson County, MC=Madison
County
SYear
1981
1982
1983
1984
1985
1986
1987
Mean
V
Maize or corn [Zea Mays (L.)] has been bred along two dis-
tinct lines. The most well known in the US are the hybrids bred
for high yield and high-energy-inputs (ie., high fertility,
irrigation, weed control, disease and insect control) that we
will designate as temperate corn. Wright, et al.(1987) have
shown the effect of planting date on temperate corn when it is
grown in a singlecrop system from early Feb to early May. We've
chosen Asgrow brand hybrid 5509 from this group. Year, planting
dates, grain yields and problems are shown in Table 3.
Table 4. Temperate corn (A5509) in relation to sowing date, har-
vest date, water use (ppt/irr), grain yield and some problems
when grown in a high-energy-input system and low-energy-input
system.
Year Sowing Harvest Applied Water ppt/ Grain Problems
Date Date N Mgt. irr yield'
(Ib/A) (in.) (bu/A)
High-energy-input
1985 28 Mar 5 Aug 260 irr. 22/5 196
1986 24 Mar 4 Aug 260 irr. 11/10 244
1987 16 Mar 10 Aug 260 irr. 22/6 175
1988 24 Mar 5 Aug 260 irr. 15/12 182
Low-energy-input
1987 16 Mar 10 Aug 260 dryland 22/0 48
1988 15 June 27 Oct 120 dryland 23/0 29 earworm and
rice weevil
Tropical corn has an interesting history. Plant breeding
knowledge was exported during the 50's and 60's (Abington, 1975)
to third world countries, hybrid seed company's picked up the
idea in the 70's and 80's and developed tropical hybrids for
third world countries that have caught the interest of farmers
and scientists in subtropical parts'of the US. Tropical hybrids
are now being imported back to the original source of knowledge.
The desirable characteristics of tropical corn are the moderate
yields that can be attained with relatively small amounts of
nitrogen fertilizer, reduced insect, disease, and weed problems,
and reduced grain storage problems in the field and granary. The
most dependable yielder that we've found in this group (recog-
nizing that we haven't extensively tested all tropical hyrids) is
Pioneer brand hybrid X-304C. Years, sowing date, harvest date,
grain yield, and some problems observed in tropical corn are
shown in Table 5.
Table 5. Tropical corn in relation year, sowing date, harvest
date, applied N, water use (water mgt., ppt/irr), grain yield,
and some problems in a low-energy-input system.
Year Sowing Harvest Applied Water ppt/ Grain Problems
Date Date N Mgt. irr Yield'
(Ib/A) (in.) (bu/A)
1985 13 June 23 Oct 120 Dryland 16/0 64 Sidedressed
late, lodging
1986 16 June 21 Oct 120 Dryland 25/0 97
1987 24 June 27 Oct 120 Dryland 15/0 96
1988 15 June 27 Oct 120 Dryland 23/0 88
1 Yields with same letter are not significantly different at the
1 % level of probability.
Planting sorghum in late May through late July results in
lower yields, because sorghum is likely to be damaged by midge,
webworm, and anthracnose during this period (Table 5). Although,
late July sorghum plantings have been been grown successfully, it
is best utilized in double-crop systems following temperate corn
10
or wheat (Wright and Gorbet, 1985) in the southeast. Sorghum
planted in late July matures around 20 Nov, and will probably
need supplemental irrigation during the predictable drought in
the Southeast in Sept, Oct and Nov This and bird, insect, and
disease problems encountered with late planting can move sorghum
into the high-energy-input category.
Table 6. Sorghum (Funk G 522DR) yield in relation to early plant-
ing (around 15 April) and late planting (around 15 June) in bu/A
from 1983 through 1988.
bu/A
Year Early Planting Late Planting
1983 92 48
1984 80 44
1985 90 24
1986 94 46
1987 88 48
Mean 89 40
1 Agronomistis of IFAS, Univ. of Fla., Florida Field and Forage
Crop Variety Reports: AY84-9, AY85-10, AY86-10, AY87-2,
AY88-02, AY89-07.
Table 7. Sorghum yields in relation to date of planting (DOP),
harvest date (HD), irrigation (I), and problems (BD=bird damage,
M=midge) for decision-making in single- or double-cropping
systems.
Funks Funks Funks Funks Funks Funks
G 522DR G 522DR G 522DR G 522DR G 522DR G 522DR
DOP 4-14-81 5-18-81 6-5-81 7-13-81 7-28-81 8-11-81
Rep bu/A
I 102 68 43 112 102 71
II 103 64 49 106 104 73
III 105 72 41 103 108 78
IV 104 72 43 107 105 74
Mean 104 69 44 107 106 74
Problems:
BD 8/27 9/28 10/8 10/8
M 7/21
I none none none Irr Irr Irr
HD 7/28 8/18 9/14 11/6 11/23 11/25
Yield, cost, price, and net return for single- and double-
crops are shown in Table 8. To calculate returns from double-
cropping, add the net returns of the two crops selected.
Double-cropping reduces production costs of the following-crop
because it can utilize residual fertility from the previous crop.
Table 8. Cost analysis of some agronomic crops grown in single- or double-crop systems in
Variable cost/acre
Fixed cost/acre
Total cost/acre
Yield (bu/A)17
Total cost/bu
Mean price ($/bu)
Net return/bu
Net return/acre
Wheat Soybean1-/
Double
82 90
30 30
112 120
62 43
1.81 2.73
2.91 5.87
1.10 3.14
68.20 138.16
Tropical Corn
Sorghum
Double Single Double1/ Doublel/
120 140 125 190
30 40 30 110
150 180 155 300
94 94 40 90
1.60 1.92 3.88 3.33
2.48 2.48 2.23 2.23
0.88 0.56 -1.65 -1.10
82.72 52.64 -66.00 -99.00
Single
140
40
180
91
1.97
2.23
0.25
Double!/
125
30
155
29
5.35
2.48
-2.87
the Southeast.
Temperate Corn
Single5/ Singlei/
240 125
110 30
350 155
200 30
1.75 5.17
2.48 2.48
-0.73 -2.69
22.75 -83.23 -199.27 -80.70
L/Nematode free yield trials at Quincy, FL.
2/Double-cropped after wheat for grain, dryland.
1/Double-cropped after corn for grain with irrigation.
!/Double-cropped after wheat for grain, dryland.
1/Irrigated.
6/Single-cropped dryland spring grown during dry year.
!/Single-cropped dryland spring grown during wet year.
I/Yields based upon research in north Florida.
-?1
I-.-T
(A
Single-/
125
30
155
90
1.72
2.48
0.76
68.40
CO
o --
u,^ i
oo
00 -!
0"
O0
On
Acknowledgements
Our thanks to E. Brown, Agric. Tech. IV, and B.T. Kidd, Biol.
Sci. II: North Fla. Res. and Educ. Ctr., Univ. of Fla.,
Quincy,FL; for data collection, computer processing, and data
illustration.
References
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Zambia. I. Evaluation of introduced material and formation of
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Florida 303 a new early maturing wheat for North Florida.
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Herzog, D.C., D.L. Wright, F.M. Shokes, and I.D. Teare. 1988.
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