EFFECT OF TILLAGE AND SOIL-APPLIED HERBICIDES ON BROADLEAF SIGNALGRASS (BRACHIARIA-PLATYPHYLLA) CONTROL IN CORN (ZEA-MAYS)

Broadleaf signalgrass control from preemergence (PRE) herbicides was u sually lower in no-till than in tilled plots, Broadleaf signalgrass co ntrol was most nearly complete in tilled plots treated with metolachlo r in 1995, a year that favored an herbicide with more soil persistence . BroadLeaf signalgrass control was most nearly complete in tilled plo ts treated with acetochlor in 1996, a year in which rainfall to activa te the herbicides did not occur until 9 d after planting. The 1996 dat a indicated that acetochlor was more stable on the soil surface under the drier conditions. There was no difference in broadLeaf signalgrass control between the two acetochlor formulations. Alachlor, metolachlo r, and dimethenamid controlled broadleaf signalgrass > 80% for about 4 wk, acetochlor provided control for about 4 wk under no-till conditio ns and about 8 wk in tilled plots, and pendimethalin provided about 2 wk broadleaf signalgrass control. Acetochlor provided consistent contr ol regardless of the rainfall pattern after application.