Agronomic Comparisons of Organic and Conventional Soybean with Recommended and High Inputs during the First 4 Years of Organic Management

Abstract

Organic soybean hectares will increase in the Northeast United States of America (USA) because of demand by the expanding organic dairy industry. We evaluated organic and conventional soybean with recommended and high inputs (high seeding rate + organic seed treatment in organic system) from 2015 to 2018 in New York, USA to determine if high input management could reduce the yield penalty in organic soybean. Organic compared with conventional soybean yielded similarly in 2015 and 2016 but ≈ 11% lower in 2017 and 2018. Organic compared with conventional soybean had similar early and harvest plant densities in 2017 but lower early and harvest plant densities in 2018 when both densities correlated with yield (r = 0.33 and 0.36, respectively). Weed densities in organic soybean were low (<0.77 weeds/m2 in all years). Nevertheless, organic compared with conventional soybean in 3 of 4 years had greater weed densities, which had significant negative correlations with yield in 2015 (r = −0.36), 2017 (r = −0.53) and 2018 (r = −0.36). Organic compared with conventional soybean mostly had fewer pods/plant and greater seed weight but yield components showed no consistent correlations with yield. Organic soybean had similar weed densities and yield with recommended and high input management in all years indicating that growers should probably plant organic soybean at recommended seeding rates (370,500 seeds/ha) during the first 4 years of organic production under similar environmental conditions of this study.