Prior cropping with grain sorghum inhibits weeds.

Three years of field data in northeastern Nebraska demonstrate that a grain sorghum crop reduces weediness in the following crop year. Weed growth was consistently lower in sorghum areas the year after strip-cropping fields with sequences of four-row bands of grain sorghum, soybeans, and corn. Percentage weed cover was significantly lower early in the year, and midsummer weed biomass was well below that found after corn and soybeans. Weed biomass in June and July following corn was two to four times that of grain sorghum strips. Inhibitory effects of grain sorghum were primarily on broadleaf weeds, often showing no action on grass weeds. No obvious differences were noted in the weed species present after the three crops. Allelopathy provides a logical explanation for the sorghum-mediated weed inhibition found in this study. The data have implications for weed management strategies in agriculture.