Cover Crop Effects on Nitrogen Availability to Corn following Wheat

Abstract

Maximizing the environmental and economic benefits of cover crops partially depends on an accurate estimate of the N fertilizer requirement of subsequent crops. Four trials involving cover crop, tillage, and N rate variables were conducted from 1992 to 1995 in southcentral Ontario on well‐drained Typic Hapludalf soils. Rye ( Secale cereale L.), oilseed radish [ Raphanus sativus (L.) var. oleiferus Metzg (Stokes)], oat ( Avena sativa L.), and red clover ( Trifolium pratense L.) cover crops were established after winter wheat ( Triticum aestivum L.) to evaluate their effects on soil NO 3 –N levels as well as subsequent corn ( Zea mays L.) grain yield response at fertilizer rates of 0 and 150 kg N ha −1 . Corn response to cover crops was compared in autumn plow and no‐till tillage systems. Within no‐till, autumn vs. spring chemical kill for red clover and rye was also evaluated. Although red clover biomass N yields were usually at least double those with other cover crops, all cover crops were equally effective at lowering residual soil NO 3 –N concentrations following wheat harvest. Presidedress NO 3 –N concentrations after autumn‐killed or plowed red clover were at least 24% higher than after any other cover crop. Grain corn yield responses indicated that red clover substantially enhanced N availability to corn in both autumn plow and no‐till systems, but that oilseed radish, oat, and rye cover crops did not enhance N availability to succeeding corn, compared with the no‐cover treatment, in either tillage system. Furthermore, the presidedress NO 3 –N test reliably estimated N fertilizer requirements of corn following all cover crop systems except spring‐killed red clover.