Summer Crop Options

for

Wheat Double-crop Systems




I.D. Teare, D.L. Wright, T.D. Hewitt
R.D. Barnett, D.W. Gorbet



















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-91-3.






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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 (cool season-crop),

harvested between 14 May and 1 June, followed by a soybean crop

(warm season-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, 1989\$5.85, and 1990\$6.25 (estimated) 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









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

warm season-crop in relation to a cool season-crop has not been

reported.

The objective of this work was to compile information about

specific yields of warm season-crops that could be used with

wheat in a double-crop system 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.

Cool season-crop

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.

Warm season-crops

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 12 inches high); 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 (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; 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 lb 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. 2. irrigation as

scheduled by tensiometers placed at 6 inch depth reached 0.02

MPa).

Asgrow hybrid brand 5509 was. planted with a no-till planter

in a prepared seedbed in rows 24 foot long 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. 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 Ib/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,
5









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

extension recommendations. Sorghum yields were corrected to 12%

moisture.

Results and Discussion

Cool season-crop

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. 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 armyworm can cause devastating

outbreaks on tropical corn). Wheat yields are shown in Table 1.

Florida 301 wheat matures around 24 May, but is susceptible to

some diseases. Florida 302 is resistant, but does not mature

until 1 June.










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)
SLate Planted State Test (12-9-87)


Warm season-crop

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.



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. Asgrow

brand hybrid 5509 was chosen from this group because of its high

yielding ability under early plantings conditions. Year,

planting dates, grain yields and problems are shown in Table 3.










Table 3. 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 that moderate

yields 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 in this group (recognizing that all

tropical hyrids have not been extensively tested) is Pioneer

brand hybrid X-304C. Years, sowing date, harvest date,









grain yield, and some problems observed in tropical corn are

shown in Table 4.


Table 4. 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
1889 26 May 30 Sept 120 Dryland 13/0 112 excess rain-
15 June 9 Oct 120 Dryland 13/0 67 fall,
29 June 27 Oct 120 Dryland 13/0 42 lodging,
17 July 16 Nov 120 Dryland 13/0 40 fall
armyworm
1990

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

(Table 6), it is best utilized in double-crop systems following

temperate corn 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 5. 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.


Early Planting
92
80
90
94


bu/A


Late Planting
48
44
24
46
48

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 6. Sorghum yields in relation to date of
harvest date (HD), irrigation (I), and problems
M=midge) for decision-making in single- or
systems.


planting (DOP),
(BD=bird damage,
double-cropping


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 each of the crops in

relation to time are shown in Table 7. To calculate returns from

double-cropping, add the net returns of the two crops selected.

Double-cropping can reduce production costs of the following-crop

because it can utilize residual fertility from the previous crop.


Year
1983
1984
1985
1986
1987

Mean










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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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Herzog, D.C., D.L. Wright, F.M. Shokes, and I.D. Teare. 1988.
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fr I *-









Wright, D.L., and F.M. Rhoads. 1981. High corn yields with
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. 11 r <