Early Preplant Herbicide Applications for No-Till Soybean (Glycine max) Weed Control

Abstract

Several field studies were conducted during 1981 and 1982 to determine whether early preplant (EPP) applications of residual herbicides would prevent the establishment of vegetation before planting no-till soybeans [Glycine max(L.) Merr. ‘Williams’]. Early preplant applications of either cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl] amino]-2-methylpropionitrile} or cyanazine plus oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) were applied in the fall and 3, 2, and 1 month(s) before planting no-till soybeans. In all studies, the treatments prevented vegetation from becoming established before planting, and season-long weed control was achieved with several different treatments. Early preplant cyanazine plus oryzalin provided greater than 90% control for the entire season where grass densities were low. Where grass densities were high (greater than 90% ground cover), EPP cyanazine plus a preemergence application of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] plus metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] or a postemergence application of sethoxydim {2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} controlled 90% of the weeds, which was equal to or better than the standard preemergence treatments used (80 to 98% weed control).