Organically Managed No-Tillage Rye-Soybean Systems: Agronomic, Economic, and Environmental Assessment

A major challenge that organic grain crop growers face is weed management. The use of a rye (Secale cereale L.) cover crop to facilitate no-tillage (NT) organic soybean [Glycine max (L.) Merr.] production may improve weed suppression and increase profitability. We conducted research in 2008 and 2009 to determine the effect of rye management (tilling, crimping, and mowing), soybean planting date (mid-May or early June), and soybean row width (76 or 19 cm), on soybean establishment, soil moisture, weed suppression, soybean yield, and profitability. Soybean establishment did not differ between tilled and NT treatments; and soil moisture measurements showed minimal risk of a drier soil profile in NT rye treatments. Rye mulch treatments effectively suppressed weeds, with 75% less weed biomass than in the tilled treatment by mid-July. However, by this time, NT soybean competed with rye regrowth, were deficient in Cu, and accumulated 22% as much dry matter (DM) and 28% as much N compared to the tilled treatment. Soybean row width and planting date within NT treatments impacted soybean productivity but not profitability, with few differences between mowed and crimped rye. Soybean yield was 24% less in the NT treatments than the tilled treatment, and profitability per hectare was 27% less. However, with fewer labor inputs, profitability per hour in NT rye treatments was 25% greater than in tilled soybean; in addition, predicted soil erosion was nearly 90% less. Although soybean yields were less in NT rye mulch systems, they represent economically viable alternatives for organic producers in the Upper Midwest.