Effects of Tillage on Sicklepod (Cassia obtusifolia) Interference with Soybeans (Glycine max) and Soil Water Use

Field experiments were conducted during 1980, 1981, and 1982 to evaluate the effect of tillage and sicklepod density on sicklepod (Cassia obtusifoliaL. # CASOB) interference with soybeans [Glycine max(L.) Merr.] and soil water use. In the absence of sicklepod, soybean yields were similar in nontilled plots covered with a straw mulch and in conventionally tilled plots with no mulch in all years. In the presence of sicklepod, higher soybean yields were obtained with the non-tilled-mulched plots than with the tilled plots at corresponding sicklepod densities and sicklepod fresh weights. Early soil water loss was greater in the tilled plots with increasing sicklepod density causing lower soil water content in both tillage treatments. Soil water depletion was greater in the no-till treatments during the soybean pod-filling stage.