SOIL COMPACTION AND CROP RESPONSE TO WHEAT/SOYBEAN INTERSEEDING

ABSTRACT Tests were conducted in Coastal Plain soils for three years to determine proper fall primary tillage for a system that supports interseeding soybean into standing wheat. The residual effects of various tillage systems and controlled traffic on soybean yield, crop response, and hardpan formation were determined. Use of a Paratill greatly reduced soil compaction, especially in the E horizon. For each tillage system, there were no significant differences in cone index values measured two and eight months after tillage in non-traffic rows. A good correlation between average soil cone index in the E horizon and soybean root length was demonstrated. Deep tillage significantly increased wheat and soybean yields. Interseeded soybean consistently yielded more than double-cropped soybean planted after wheat harvest at irrigated and non-irrigated locations. Due to controlled traffic patterns associated with the interseeding system, only one deep tillage operation before small grain seeding is required for the wheat/soybean double-cropping system. The residual effect of deep tillage operations will extend for one additional year when interseeding is practiced in costal plain soils.