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Weed emergence and in -row weed control in dry bean
Weed seedlings emerging with dry bean (Phaseolus vulgaris) or soon thereafter are a major problem because they interfere with crop growth and development more than later emerging weeds. Mechanical practices like between-row cultivation usually control weeds located away from crop plants, but one of the major concerns of dry bean producers is the growth of weeds located on the crop row. Dry bean yield reductions by weeds growing in the crop row may be avoided by timely control of weeds with rotary hoeing, in-row cultivation, and chemical methods. Field experiments were conducted in 1996 and 1997 to (1) evaluate the effect of mechanical cultivation, herbicides, and dry bean on weed seedling emergence; and (2) evaluate weed control and dry bean response to singular or combinations of rotary hoeing, in-row cultivation, and herbicides. Total weed emergence in 1996 and 1997 was similar in cropped and noncropped areas. Herbicides were more effective than mechanical cultivation in reducing weed emergence by 91% in 1996 and 88% in 1997. Initial weed seedling emergence was observed at about 120 TT units with 3 to 9% cumulative emergence in 1996, while weed emergence was first observed at 80 TT units with 6 to 16% cumulative emergence among treatments in 1997. In both years, there was a trend for weed emergence in the untreated control and rotary hoed plots to be 26% on average lower in cropped areas than in noncropped areas implying a competitive effect by the dry bean crop. Although weed seedling emergence occurred throughout the growing season more weed seedlings emerged in June and early July than in late July and August. Therefore, these data support the importance of applying mechanical in-row weed control treatments early in the growing season when a majority of the weed seedlings are emerging. The effect of dry bean on weed emergence was accurately modeled by the Gompertz function, but models developed to predict weed emergence when rotary hoeing and in-row cultivation were used failed to accurately predict weed emergence. Dry bean stands were not reduced by rotary hoeing, in-row cultivation, and herbicides in 1996, but in-row cultivation reduced dry bean population by 21% compared to rotary hoeing in 1997. Difference in dry bean yields between years was due to different weed densities. Weed density in 1996 was 35 plants/m 2 and in 1997 was 135 plants/m2. The combination of EPTC plus ethalfluralin applied alone or combined with rotary hoeing or in-row cultivation had lower weed densities than dimethenamid or imazethapyr plus bentazon. Among herbicides, the group of treatments with dimethenamid had 23 and 53% lower dry bean seed yields than the group of treatments with EPTC plus ethalfluralin that had the highest seed yields in 1996 and 1997, respectively. ^
Amador-Ramirez, Mario Domingo, "Weed emergence and in -row weed control in dry bean" (1999). ETD collection for University of Nebraska - Lincoln. AAI9942109.