Interseeded cover crops, soil health, and nitrogen supply for grain corn in Ontario
Interseeded cover crops are a promising option for improving environmental sustainability in corn-based rotations. Field plots were established in 2015 under conventional tillage and regional corn N fertilization practices and repeated over two seasons at three sites in southern Ontario: Ridgetown, Elora, and Peterborough. The objectives were to evaluate the effects of interseeded annual ryegrass (ARG) and red clover (RCL) on grain corn yield and N uptake; soil mineral N (Nmin); and soil biological parameters. At each site, ARG, RCL, an ARG/RCl blend (MIX), and a no-cover control (BARE) were arranged in a RCBD replicated four times. The cover crops were seeded between the corn rows at the 5-leaf stage using an InterSeederTM drill. Cover crops accumulated 15 - 860 kg C ha-1 and 1.3 - 77 kg N ha-1 per season, and their yields were significantly correlated with soil microbial biomass, β-Glucosidase activity, and particulate organic matter. Community-level physiological profiling (BIOLOG EcoplatesTM) showed that microbial community diversity was significantly greater in ARG than BARE. Grain N concentration (10.8 - 11.2 g kg-1) and aboveground corn N uptake (100 - 154 kg ha-1) were not significantly reduced by cover crops at all sites. Although residual Nmin levels measured at grain corn harvest (0-30 cm) and the following spring (0-15 cm) were generally low (2.4 - 9.3 mg kg-1) at all sites, ARG had 48% lower Nmin than BARE. The effects of cover crops on soil health parameters, corn N uptake and Nmin were more affected by site and seasonal variability than by cover crop treatments. However, the results indicate the potential for improving soil health when there is successful establishment of interseeded annual ryegrass or red clover.
Soils and Crops Workshop