Minimizing Interspecific Competition in Soybean by Optimizing Cover Crop Self-Seeding

Developing self-seeding cover crop systems that minimize interspecific competition with soybean [Glycine max (L.) Merr.] are possible if cover crop growth is restricted to optimize cover crop seed production and dispersal. The objectives of this research were to quantify cover crop seed production, viability, and self-seeding when growing concurrently with soybean. Winter wheat (Triticum aestivum L.), triticale (X Triticosecale Wittmack), and rye (Secale cereale L.) were seeded at two target rates (99 and 198 seeds m−2). Three seed dispersal methods (natural seed rain, simulated combine, and mechanical preharvest) were also tested to disperse mature cover crop seed. Wheat combined with mechanical seed dispersal before soybean harvest exhibited the greatest consistency in self-seeding (171 and 123 plants m−2 in 2007 and 2008) regardless of establishment seeding rate. Additionally, wheat averaged 51 and 32% green groundcover in the fall of 2007 and 2008. Wheat seed viability (>82%) exceeded rye and triticale at soybean harvest, approximately 60 to 80 d after seed maturity. Cover crop species or establishment seeding rate did not affect soybean seed yield either year. Averaged across seeding rate and seed dispersal treatments, wheat self-seeding systems exhibit the greatest potential for adoption, although soybean yield was 27% lower in 1 of 2 yr compared with a no cover crop control.