1989 Annual Report for LS89-012
Enhancing Farmer Adoption and Refining of a Low-input Soybean-Wheat System
Summary
Research and Extension personnel at Mississippi State University have developed a low-input soybean-wheat intercropping system which involves mechanically planting soybeans between standing rows of wheat spaced 15-16 inches apart at the time the wheat grain is in the medium-soft dough stage. The year 1988 was the sixth year of research and development work on this system for planting soybeans into wheat using an established tractor wheel track skip (30-inch skips 2/20 ft. planter swath). The system reduces soil erosion potential, tillage and herbicide input costs, increases soybean yield and results in higher net returns than conventional monocrop soybeans and other soybean-wheat double-cropping systems. The system has practical application to small and medium-sized farms through improved net returns on the same land area without increasing acreage farmed.
This project involves the USDA/Agricultural Research Service, Soil Conservation Service, farmers, Extension and Research personnel in Mississippi, and farmers and Extension personnel in Arkansas. The purpose is to enhance the adoption of this low-input intercropping system and participate in further refinement of this system for small to medium-sized farms in these two states. The project (1989-92) involves seven Mississippi farms, three Arkansas farms, and two experiment stations. The highly variable weather conditions and low commodity prices during this study resulted in the cancellation of some of the farm studies during the life of this project. Most of the on-farm study results indicated that perennial winter weed (e.g. horseweed) control failures in the wheat carried over into the subsequent relay planted (RP) soybean crop and were not controlled with currently available postemergence soybean herbicides. In addition, soybean weed (e.g. spotted spurge and ragweed) control failures were also noted where postemergence herbicides were not applied immediately following winter wheat harvest. The lack of good weed control had a significant effect on causing lower soybean yield. This is in sharp contrast to soybeans planted in wheat stubble in late June which received a burndown herbicide that provided excellent weed control.
Economic analysis of selected farm studies indicated that three of six farm-yrs. (farm x yrs), the RP system produced higher net return than planted in wheat stubble in late June. Five of seven farm-yrs, the monocrop soybeans produced higher net return than either doublecropping system. The higher net return for monocrop beans was partially due to ineffective weed control which caused lower yield in the RP system. The decline in burndown herbicide costs (as much as 50%) in recent years, also, lowered the direct cost for the wheat stubble system.
One year (1990) of evaluating wheat row spacings postemergence herbicides, and cultivation combinations for weed control indicated that a high clearance no-till cultivator was not able to maneuver through the wheat stubble in the narrower (30-inch) soybean rows. Most high clearance cultivators work best with wider row spacings (36-40 inches).
The raised wide-bed RP system, on poorly drained soils, increased wheat yield two of three years for a three year average of 13% more than planted flat; but had no effect on soybean yield. SCS soil erosion estimates indicated that both wheat-soybean doublecropping systems (relay planting and planting in wheat stubble) reduced soil erosion about 25-40% compared to monocrop conventional tilled soybeans. The first year (1992) evaluation of 26 soybean cultivars relay planted into wheat indicated that most cultivars were more sensitive to this intercropping culture than planted as a monoculture on the same date. However, some cultivars showed less sensitive to the intercropping culture than other cultivars.
Objectives
(1) Enhance small and medium-sized farm adoption of a low-input reduced-tillage intercropping system for relay interplanting of soybeans in wheat.
(2) Refine this system by evaluating narrow wheat row spacings alone and in combination with reduced herbicide inputs and cultivation for enhanced wheat yield and weed control.
(3) Demonstrate lower input costs and enhanced profitability for low-input soybean-wheat intercropping system.
(4) Evaluate this system on soils with poor surface drainage using a wide-bed system.