Analysis of seedbeds and maturity groups for dryland soybean on clayey soil

Soybean [Glycine max (L.) Merr.] production systems on clayey soils are dif ficult to manage. With improvements in no-till planting equipment and herbi cide technologies in the early 1990s, no-till production has become a viabl e alternative to the traditional tilled seedbed. Therefore, the relative ec onomic performance of tilled and no-till seedbeds with respect to profitabi lity, sensitivity to input price changes, and risk is assessed for maturity group (Md) IV, V, and VI soybean. Field experiments using split plots (mai n plots were MG and subplots were seedbeds) and a randomized complete block design with four replications were conducted from 1992 to 1994 at Rohwer, AR and from 1990 to 1997 at Keiser, AR on Sharkey and Sharkey silty clay, r espectively, The importance of weather conditions is highlighted in the var ied seedbed preparation effect on grain yields, with no clear advantage to either method. On average, yields were higher for MG IV at Rohwer and MG VI at Keiser. The breakeven price and yield analysis suggested that MC select ion had a larger economic impact than seedbed preparation, regardless of lo cation. This analysis also showed the extent of production cost differences and associated risk of loss by location. Risk analysis revealed that optim al production strategies changed when input rests were added to yield infor mation and further confirmed that MG selection affects profitability more t han seedbed preparation. Production practices that better exploit the yield potential of various MG cultivars (as related to weather conditions) there fore deserve further research attention.