Cover crop species and termination method effects on organic maize and soybean

Mechanical cover crop (CC) termination can reduce tillage in organic rotations, but research is needed to develop recommendations for producers in the upper Midwest, U.S.A. Field studies were conducted near Concord, NE, U.S.A., in 2008-2009 and 2009-2010. This study compared no-till [roller/crimper (CRIMP) and broadcast propane flame (FLAME)] and spring disk (DISK) termination of legume, grass, and broadleaf CCs and their effects on a subsequent maize or soybean crop. Before sowing the grain, overwintering CC species were terminated; frost-killed (FROST) CCs were also disked in the spring. Weeds were controlled via cultivation in the tilled systems (DISK and FROST); CC residue was left as a surface mulch in the no-till systems (CRIMP and FLAME). Termination method/tillage regime had greater influence than CC species on grain yield and quality, with tilled treatments performing better than CRIMP and FLAME, likely due to early season weed pressure and low stand establishment in the no-till treatments. Maize yield for the DISK system was on average 6.8 Mg ha(-1) in both trials, while FLAME and CRIMP produced 57-78% less. Soybean yields for DISK were 3.3 and 2.0 Mg ha(-1); CRIMP and FLAME produced 21-33% less in 2009 and 56% less in 2010. The CCs best suited to no-till systems were winter rye (superior biomass) and hairy vetch (successful mechanical termination). FLAME performed as well as CRIMP. The results suggested that no-till CC termination should be employed within a comprehensive weed management system to minimise yield losses due to weeds and CC regrowth.