Weed Control in Navy Bean in Reduced Tillage Systems

Abstract

Concern over soil erosion and high production costs in conventional tillage systems has led to interest in reduced tillage systems for navy bean (Phaseolus vulgaris L.). Research was conducted for 2 yr at two sites with different 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 Michigan. Weed management strategies included hand-weeding, cultivation-only, preemergence herbicides, preemergence followed by postemergence herbicides, and postemergence herbicide treatments. Glyphosate was applied to control 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 moldboard plow and chisel plow systems. Imazethapyr plus pendimethalin preemergence provided less weed control than preemergence followed by postemergence and total postemergence treatments in two of four site years. Preemergence followed by postemergence herbicides controlled annual broadleaf weeds better than postemergence herbicides alone. Navy bean seed yield at the sandy 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-tillage systems had the highest gross margins. These data suggest that weeds can be controlled in reduced tillage systems and the success of reduced tillage systems in dry bean production varies by soil texture. Research Question Navy bean production in reduced tillage systems offers the potential for lower production costs and reduced soil erosion and sedimentation into waterways. Information on weed control methods in navy beans planted in reduced tillage systems is lacking. This research was initiated to determine the potential for notillage and zone-tillage navy bean production with emphasis on weed management systems. Our objective was to determine whether navy bean could be successfully grown in minimum tillage systems and to develop weed management strategies for these production systems. Literature Summary Previous research suggests that tillage may be necessary to loosen compacted soil, control weeds, incorporate fertilizer, lime, herbicides, and crop residue, and reduce insect pests and plant diseases. Navy beans are more sensitive than soybeans to soil compaction. Yield reductions in navy bean have occurred on fine clay soils that were vulnerable to compaction from tire traffic. Study Description Field experiments were conducted in 1995 and 1996 in Ingham county on sandy loam soils and in Huron county on sandy clay loam soils in Michigan. There were 12 weed management treatments in various tillage systems. The tillage systems in Ingham county included: (i) spring chisel plow, (ii) zone-till, (iii) no-till corn stalks chopped, and (iv) no-till. The tillage systems in Huron county included: (i) fall moldboard plow, (ii) fall chisel plow, (iii) zone-till, (iv) no-till, and (v) no-till with row cleaners. Weed management treatments at both locations included: imazethapyr + pendimethalin preemergence; metolachlor or dimethenamid preemergence followed by imazethapyr + bentazon + crop oil concentrate, fomesafen + bentazon + crop oil concentrate, or acifluorfen + bentazon + crop oil concentrate applied postemergence; and total postemergence treatments of imazethapyr + bentazon + crop oil concentrate, fomesafen + bentazon + crop oil concentrate, and acifluorfen + bentazon + crop oil concentrate. Handweeded and cultivation-only controls were included. Glyphosate at 1 qt/acre was applied to all zone-tillage and no-tillage systems 2 wk prior to planting and again immediately after planting. Navy beans were planted in 30 in. rows and cultivated twice. Plots were harvested by direct cutting and yield and gross margins determined. Applied Questions Did weed populations differ among tillage systems? Weed populations were lowest in the no-till system, greater in the intermediate zone-till system, and highest in the conventional chisel and moldboard plow systems. Can weeds be controlled throughout the growing season in navy bean grown in reduced tillage systems? Weeds were controlled in all the tillage systems with residual herbicides followed by cultivation. In minimum tillage systems, weeds were controlled without a residual herbicide when glyphosate was applied at planting to control emerged weeds followed by cultivation. The minimum tillage system with the least amount of soil disturbance (no-till) generally resulted in the lowest weed populations throughout the growing season. Did navy bean population or yield differ among tillage systems? Plant populations were lower in no-till than in conventional tillage systems. Navy bean yield was equal among tillage system on a sandy loam soil. However, on a sandy clay loam soil, seed yield was greatest in the moldboard plow tillage system and lowest in the no-till system. Were any of the herbicide programs injurious to navy bean? Acifluorfen + bentazon applied postemergence caused 12% visual injury 7 d after application, with injury diminishing over time. Acifluorfen is not registered for use in dry edible beans. This injury did not reduce navy bean seed yield. Which weed management program provided the best weed control? All preemergence followed by postemergence herbicide applications resulted in excellent weed control. Control of annual grass (giant foxtail and fall panicum), redroot pigweed, and common lambsquarters from imazethapyr + pendimethalin preemergence was less than control with other herbicide treatments in two of four site years. Common lambsquarters control from imazethapyr + bentazon and acifluorfen + bentazon postemergence was lower compared with other herbicide treatments in one of four site years. Which weed management program resulted in the highest gross margins? At one location, imazethapyr + pendimethalin resulted in the highest gross margin ($314/acre), while at the second location, cultivation only (no herbicide applied except glyphosate) resulted in the highest gross margin ($188/acre). Weed populations were low (<1 weed/ft) in both years where cultivation-only resulted in the highest gross margins. In conditions with higher weed populations, herbicides were needed to maintain navy bean yield. Could navy bean be produced in reduced tillage systems and maintain plant populations, yield and resulting gross margins comparable with conventional tillage systems? Plant populations were lower in no-till than in conventional tillage regardless of soil type. On a sandy loam soil navy bean seed yields and gross margins were similar in all tillage systems. When planted on a sandy clay loam soil, navy bean yield and gross margin were lower in no-till. These data suggest that growers should avoid no-till navy bean production on fine-textured soils.