Weed control in navy bean in reduced tillage systems

Concern over soil erosion and high production costs in conventional tillage systems has led to interest in reduced tillage systems for navy bean (Phas eolus vulgaris L.). Research was conducted for 2 yr at two sites with diffe rent soil textures to develop weed management strategies in reduced tillage systems for navy bean. Twelve weed management strategies were evaluated in conventional tillage, no-till, and zone-till systems in 1995 and 1996 in M ichigan. Weed management strategies included hand-weeding, cultivation-only , preemergence herbicides, preemergence followed by postemergence herbicide s, and postemergence herbicide treatments. Glyphosate was applied to contro l existing vegetation in the no-till and zone-till systems. Redroot pigweed (Amaranthus retroflexus L.) and common lambsquarters (Chenopodium album L. ) populations were lower in the no-till and zone-till systems than in the m oldboard plow and chisel plow systems. Imazethapyr plus pendimethalin preem ergence provided less weed control than preemergence followed by postemerge nce and total postemergence treatments in two of four site years. Preemerge nce followed by postemergence herbicides controlled annual broadleaf weeds better than postemergence herbicides alone. Navy bean seed yield at the san dy clay loam site was 50% higher in moldboard plow and chisel plow tillage systems than in the no-tillage system. The highest average gross margin was in the chisel plow system. There was no difference in navy bean seed yield due to tillage system at the sandy loam site and the no-tillage and zone-t illage systems had the highest gross margins. These data suggest that weeds can be controlled in reduced tillage systems and the success of reduced ti llage systems in dry bean production varies by soil texture.