Planting date, cultivar, and tillage system effects on dryland soybean production

Soybean [Glycine max (L.) Merr.] yields from nonirrigated fields in the midsouthern USA have consistently lagged behind those from irrigated fields. Nonetheless, nonirrigated fields still attract a larger share of soybean acreage in this region. This is likely due to various irrigation constraints, which include land-leasing arrangements, water shortage, lack of management time, and low levels of operating capital. The objective of this study was to identify production system components consisting of tillage, cultivar selection, and planting-date strategies for a soil series that are most suitable for enhancing economic returns to dryland soybean. Data from field experiments in three Arkansas locations in 1995 and 1996 were used for the study. Leading production systems were identified on the basis of their net returns. Results of the study show that the performance of the production systems in terms of crop yields and net returns is influenced by location and production year. While the evidence on pure planting-date effects is confounded with physical field location, cultivar yields from early soybean plantings in April and May are generally higher than those from later plantings. Furthermore, conventional and fallow production systems had higher net returns than no-till systems, largely due to higher herbicide costs associated with no-till systems. Sensitivity analysis showed that planting date and seedbed preparations are robust to changes in herbicide, fuel, and soybean prices. Further, careful attention to cultivar selection is deemed appropriate because cost differences of cultivar seeds are minor relative to net return differences that are yield driven.