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Cropping Systems


The alluvial soils and climate in the upper Mississippi Delta region allow farmers to grow rice, cotton, corn, soybean, sorghum, and wheat. Crop prices, input costs, and yield potential are important factors in determining what crop is planted in a field each year. Common crop rotations in the region are corn/soybean/wheat and rice/soybean. Many of the fields are laser leveled for improving drainage. Ridge-tillage cotton with winter wheat planted in the row middles is often used to prevent blowing sand injury to cotton seedlings.


Below is information on several cropping systems.

Missouri Rice Growth Stage Prediction Model (DD-50) Irrigation of Pharmaceutical Tobacco
Pollen Movement from Genetically Modified Corn Corn After Corn
Flood Tolerance in Soybean Varieties

The Missouri Rice Growth Stage Prediction Model Degree-Day 50 program is available to help rice farmers manage their fields. This program uses maximum and minimum daily air temperatures to predict when rice growth stages will occur in a field. The program assumes rice growth will not occur with average temperatures below 50°F. The objective of this program is to improve timeliness of rice management decisions by utilizing temperate data from the Commercial Agriculture weather station network. DD-50 reports generated early in the season are based on long term weather averages. As the season progresses new reports can be made with updated rice growth predictions based on weather that has occurred in the season.

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corn detasseling
Hand detasseling corn treatments at Wardell,
Missouri for a pollen confinement experiment.

Pollen Movement from Genetically Modified Corn. A three-year study was conducted in Wardell, Hayti, and Clarkton to evaluate cross pollination (gene flow) from transgenic corn fields. Corn inbreds were planted in a 10-acre block in the center of three 160-acre cotton and bean fields. Within the 10-acre blocks, four rows of yellow kernel females were alternated with four rows of white kernel males. Yellow corn varieties with transgenes were planted for tracing gene flow. Female rows were detasseled by hand with some of the plants intentionally missed. Levels of detasseling were 0%, 80%, 90%, and 100%. At 660 and 900 feet from the pollen block, white corn trap plots were planted on three dates in strips. Results showed that the greatest amount of cross-pollination, as detected by seed color and polymerase chain reaction, was to white corn trap plots located 660 feet north of pollen blocks and was associated with pollen from yellow corn with no detasseling. Incidence of yellow kernels was 0.0301%. At 900 feet, gene flow was 0.0013% from 90% detasseled corn. When 100% of the corn was detasseled, no gene flow was detected at 900 feet. More info. Crop Sci 44:1271-1277, APHIS workshop PowerPoint

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Flood tolerance in soybean varieties. In the Delta, waterlogged soil often reduces soybean yields. Symptoms of waterlogged soil stress in soybean may include leaf yellowing, reduced root growth, reduced nodulation, stunted growth, defoliation, reduced yields, and plant death. Waterlogged soil may damage plants directly or indirectly through enhanced plant disease. A two-year experiment was conducted on loam and clay soils to evaluate the tolerance of soybean varieties to waterlogged soils at varying growth stages and flood durations. Research with five soybean varieties demonstrated that short-term flood irrigation can be done without reducing soybean yields. In flood duration experiments, DK 4868 and P94B73 produced higher yields than other varieties in extended waterlogged soils. Visual injury ratings from screening work showed no complete tolerance to soil waterlogging by any of the tested Group III, IV, or V soybean varieties. However, some differences were found in flood tolerance that will be used in soybean breeding programs. M. Rhine M.S. Thesis

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Irrigation of Pharmaceutical Tobacco. A group of scientists from University of Missouri-Delta Center, USDA, and Chlorogen, Inc. teamed up to study soil water potential affects of protective antigen for anthrax produced in chloroplast transformed Petite Havana tobacco. Tobacco plants with protective antigen genes were transplanted into native soil in a greenhouse floor rather than growing plants in pots. This was done to simulate conditions in a large high tunnel greenhouse where tractors and other machinery are used to reduce production costs. Results showed that increasing biomass with optimum irrigation did not dilute protective in leaves. Applying too much irrigation water was as detrimental to leaf biomass production as not applying enough water. Genetic engineering tobacco for protective antigen caused reduced leaf area in plants. Transpiration was significantly higher with non-transgenic plants indicating that lower irrigation rates may be needed for antigen tobacco. Agron J 99:1271-77. Request Reprint

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audio Planting continuous corn
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Corn after Corn. On average, continuous corn fields produce 10% less yield than rotated corn. But there are ways to reduce this gap and make equal yields in non-rotated corn. In continuous corn, farmers should be on the alert for increased disease, weed, insect and fertility problems. Basically, all the problems that you encounter with rotated corn are magnified in continuous corn.

Gray leaf spot may be worse in continuous corn because the fungus in the old residue can infect corn plants. Avoid having more than 35% of the soil covered with old stubble. Select varieties with good gray leaf spot resistance and consider applying Headline or Quatris at tassel stage. Dr. Melvin Newman at University of Tennessee has found that these chemical applied at 6 ounces per acre are effective. But, growers should be aware that there is a narrow application window. Applying after silking begins, can cause injury to ears. Corn root worm is potentially increased in continuous corn. To combat the problem, look for varieties containing Bt genes for CRW resistance. The normal Bt gene for other worms often is not effective. Also consider in-furrow insecticides for corn root worm. The biggest weed challenge may be volunteer corn. If you had conventional corn in 2007, select a Roundup Ready or Liberty Link variety. If you had Roundup Ready in 07 plant Liberty Link in 08. Or vice versa if you had Liberty Link in 07.

Most of the time, we recommend uping the N rate 20% in continuous corn but that is not always necessary. Sometimes there is more residual soil N left over from corn than soybeans. The problem is the corn residue is higher in carbon than soybean stubble and the soil microbes can immobilize N from the soil. When the corn is 1 to 2 feet tall consider taking a pre-sidedress N soil sample down to 2 feet. The Delta Center soil lab can tell you how much N you need from that test. An alternative method is to collect corn tissue samples and bring them in for testing.

As you begin planning for next year, select fields carefully. Irrigated fields with highly productive soils show less yield drag from continuous cropping than dryland fields with marginal soils. Residue buildup and soil compaction are greater problems in continuous corn than corn following soybean. No-tillage fields often have a larger yield reduction than tilled fields. Finally, select corn varieties very carefully. Sometimes it is a challenge finding a top-yielding variety with the gray leaf spot and corn root worm resistance traits that you need for continuous corn.

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