Response Of Soybean To Deep Tillage With Controlled Trafhc On Clay Soil

A three-year field study was conducted on a Tunica clay (clayey over loamy, montmorillonitic, nonacid, thermic Vertic Haplaquept) to evaluate the combined effects of deep tillage and controlled traffic on soybean (Glycine max [L.] Merr.) yield and on the soil moisture availability. In an irrigated environment, yields from all deep-tilled treatments were statistically similar to yields from conventional disked check treatments. Moisture sensors located at the 15 and 45 cm depths in the irrigated plots indicated moisture tension in all treatments was maintained at less than 1 bar in 1987 and near 2 bars in 1988. However, in the nonirrigated environment where moisture deficits and subsequent plant stress were a function of the rainfall pattems, yields from all deep-tilled treatments were statistically similar and 73% higher than yield from the nonirrigated check treatment in 1987 and 132% higher in 1988. Moisture tension in the check treatment of the nonirrigated environment in 1987 and 1988 was noticeably higher than all deep-tilled treatments during reproductive stages R3 to R6. The higher moisture stress in 1987 and 1988 significantly reduced soybean yields and number of seed produced in the check treatment.