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 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.

Nitrogen cycling, profit margins and sweet corn yield under fall cover crop systems

“…At Ridgetown, OSR and OSR&Rye had higher biomass and plant N content compared with that observed by Vyn et al (2000) and Weinert et al (2002). The high plant N content in OSR and OSR&Rye treatments at Ridgetown was likely due to the fact that plants reached physiological maturity and set viable seed.…”

“…Thus, at both sites, in 8 of the 11 sample times, there were no differences among planted cover crops in the quantity of N immobilized in plant tissue. Vyn et al (2000) also found no difference in cover crop N content among rye, oat and OSR sampled in late fall in a 3-yr study in southern Ontario. Similar to Bothwell in December and Ridgetown in October, Wagger (1989) …”

“…Plant N content of both OSR treatments was not inconsistent with canola at maturity, where plant N content, including dropped leaves, was 300 kg N ha (1 (assuming plant density of 100 plants m (2 ) (Svecnjak and Rengel 2006). Vyn et al (2000) suggested that low soil NO ( 3 -N after wheat harvest restricted the growth of non-leguminous cover crops. At pea harvest, there was at least 94 kg N ha (1 of soil mineral N in the 0-to 60-cm depth, which was considerably higher than that observed after wheat (Vyn et al 2000) and likely contributed to higher cover crop biomass and N content in our study.…”

“…Vyn et al (2000) suggested that low soil NO ( 3 -N after wheat harvest restricted the growth of non-leguminous cover crops. At pea harvest, there was at least 94 kg N ha (1 of soil mineral N in the 0-to 60-cm depth, which was considerably higher than that observed after wheat (Vyn et al 2000) and likely contributed to higher cover crop biomass and N content in our study. Moreover, the earlier harvest of pea and cover crop planting in our system compared with wheat (Vyn et al 2000), resulted in more growing degree days for more cover crop growth (Table 2 and 3).…”

“…Based on a cover crop N content of 100 kg N ha (1 (Weinert et al 2002), sweet corn acreage in Canada and N fertilizer cost of $1 kg (1 , this would amount to a $0.6 to $1.65 million reduction in N fertilizer input costs for growers. However, in order to reduce N fertilizers without compromising yield, cover crop N mineralization should be in synchrony with N demand of the following crop (Vyn et al 2000;Weinert et al 2002).…”