High seeding rates, interrow mowing, and electrocution for weed management in organic no-till planted soybean

Abstract

No-till planting organic soybean [Glycine max (L.) Merr.] into rolled-crimped cereal rye (Secale cereale L.) can have several advantages over traditional tillage-based organic production. However, suboptimal cereal rye growth in fields with large populations of weeds may result in reduced weed suppression, weed-crop competition, and soybean yield loss. Ecological weed management theory suggests that integrating multiple management practices that may be weakly effective on their own can collectively provide high levels of weed suppression. In 2021 and 2022, a field experiment was conducted in central New York to evaluate the performance of three weed management tactics implemented alone and in combination in organic no-till soybean planted into both cereal rye mulch and no mulch: 1) increasing crop seeding rate, 2) inter-row mowing, and 3) weed electrocution. A nontreated control treatment that did not receive any weed management and a weed free control treatment were also included. Cereal rye was absent from two of the five fields where the experiment was repeated; however, the presence of cereal rye did not differentially affect results and thus data were pooled across fields. All treatments that included inter-row mowing reduced weed biomass by at least 60% and increased soybean yield by 14% compared to the nontreated control. The use of a high seeding rate or weed electrocution, alone or in combination, did not improve weed suppression or soybean yield relative to the nontreated control. Soybean yield across all treatments was at least 22% lower than the weed free control plot. Future research should explore the effects of the tactics tested on weed population and community dynamics over an extended period. Indirect effects from inter-row mowing and weed electrocution should also be studied, such as the potential for improved harvestability, decreased weed seed production and viability, and the impacts on soil organisms and agroecosystem biodiversity.