Identifying Soybean Traits of Interest for Weed Competition

Abstract

ABSTRACT Organic soybean [ Glycine Max (L.) Merr.] producers rely on a variety of tactics for weed management. The use of soybean cultivars with enhanced ability to compete with weeds may increase weed control. Our objective was to identify genetic traits that may enhance soybean's competitive ability to suppress weeds. Experimental design was a split‐split plot with sets of contrasting soybean genotypes assigned to the main plots, individual genotypes assigned to subplots, and weedy and weed‐free sub‐subplots stripped across blocks for side by side comparison of treatments in weedy and weed‐free conditions. Differences in weed biomass were detected among genotypes in both years at 7 wk after emergence. Narrow‐leaflet small‐seeded natto types were generally poor competitors with weeds. Cultivars released as forage types did not have a consistent advantage over the control. Larger‐seeded tofu genotypes were also variable in weed suppressive ability. However, N04‐8906, the genotype with the greatest 100‐seed weight in this study (24 g), stood out as being among the best for weed suppression, soybean biomass accumulation, ground cover at 3 wk, and early season plant height. Optimum models from multiple regression showed seed size to be the most significant trait measured in overall genotype competitive ability in both years. However, seed size effects on ground cover largely dissipated by 5 wk after emergence.