Comparing Methods for Overseeding Winter Rye into Standing Soybean

Abstract

Core Ideas: Several methods of overseeding a winter rye cover crop into soybean were tested. Tractor-mounted seeders reduced soybean yield by 4% relative to an aerial seeder. Each seeder was equally variable across the seeding path with an average CV of 34%. Rye growth was influenced by weather and possibly by seeding density (a covariate). Seeding rate and timing may be more important factors than choice of equipment. In the upper Midwest, short growing seasons make it difficult to establish cover crops in corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations. Overseeding before cash crop harvest may allow more time for growth, but practical methods need to be evaluated. Over 2 yr, this study assessed three winter rye (Secale cereale L.) overseeding techniques into standing soybean in mid-September: aerial seeding (AS), tractor-mounted air-flow spreader (TAF), and tractor-mounted fertilizer broadcast spreader (TBS). All treatments had equal variability in seeding density across plots. When rye was overseeded using the TAF and TBS treatments, soybean yield was reduced by approximately 4% relative to the AS treatment. In spring, seeding treatments impacted aboveground biomass production and N uptake in a year with good growing conditions (2010–2011), but not in a year with poor growth conditions (2011–2012). The impact of seeding method in the first year of the study was more likely due to differences in seeding density of the treatments, which was used as a covariate in this study. In a year with good growing conditions, the treatments with lower seeding densities had more spring biomass production, likely due to compensatory growth. Overall, measured values of aboveground biomass ranged from 39 to 467 kg ha−1, whereas aboveground N uptake ranged from 2.1 to 15.3 kg ha−1. Based on these findings, research efforts should focus on evaluating optimal seeding rates and timing, rather than choice of seeding method, to reduce impact on soybean yields and maximize cover crop benefits.