Cover Crop Effects on Nitrogen Availability to Corn following Wheat
2000
Vyn, Tony J. | Faber, John G. | Janovicek, Ken J. | Beauchamp, Eric G.
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 NO₃–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 NO₃–N concentrations following wheat harvest. Presidedress NO₃–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 NO₃–N test reliably estimated N fertilizer requirements of corn following all cover crop systems except spring-killed red clover.
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