Soil Nitrate Accumulation and Corn Response to Preceding Small‐Grain Fertilization and Cover Crops

Abstract

Potential benefits associated with establishing cover crops, such as reduced NO3 leaching risk and lower fertilizer N requirements for succeeding crops, will be fully realized only when the cover crop N contribution is accurately accounted for and availability is synchronous with succeeding crop N demands. The objectives of this study were to evaluate spring soil NO3−N accumulation patterns and N availability to corn (Zea mays L.) following annual ryegrass (Lolium multiflorum L.), oilseed radish [Raphanus sativus (L.) var. oleiferus (Stokes) Metzg.], red clover (Trifolium pratense L.), and no cover crop established after either winter wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.). The wheat and barley were produced with 0.5, 1.0, and 2.0 times the amount of recommended N fertilizer. Six field trials were conducted on well‐drained Typic Hapludalf soils in southwestern Ontario intermittently from 1989 to 1995. Corn was produced using a spring mulch‐till system with only 10 kg ha−1 of fertilizer N, which was applied as part of the P starter fertilizer. Applying more fertilizer N to the previous year's small‐grain crop rarely increased spring soil NO3−N concentrations or corn yields. Soil NO3−N concentration increases between the May and June sample dates following annual ryegrass and oilseed radish did not differ substantially from where a cover crop had not been established; following red clover, however, NO3−N increases were always at least 2.8 times greater than after no cover crop. Average aboveground corn biomass N at anthesis following annual ryegrass was 25.6 kg ha−1 less than when no cover crop was grown, whereas following red clover it was 40.4 kg ha−1 greater than with no cover crop. Corn yields were consistently the highest following red clover and often the lowest following annual ryegrass; yield response was positively correlated with June soil NO3−N concentrations (r = 0.61‐0.93). These results suggest that N availability to succeeding corn differs among the cover crop treatments evaluated in the order red clover > oilseed radish ≥ no cover crop > annual ryegrass.

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

“…In the following growing season, the lack of increase in soil mineral N in nonleguminous cover crop treatments compared with nocover was consistent with other research (Wagger 1989;Vyn et al 1999). It is possible that net N mineralization of cover crops did not match up with sweet corn N demand.…”

“…In the 60-to 90-cm soil depth at Ridgetown, soil mineral N was unaffected by cover crops compared with the nocover with the exception of soil mineral N being lower under rye than no-cover in May (Table 6). The observed trend of net N immobilization of rye was consistent with Vyn et al (1999).…”

“…The lack of differences among the cover crops in soil mineral N in the following spring was consistent with Vyn et al (1999).…”

“…Sweet corn total plant N at harvest ranged from 88 to 116 and from 170 to 205 kg N ha (1 at Bothwell and Ridgetown, respectively. Inconsistent effects of cover crops on both sweet and field corn plant N have been noted in the literature (Bundy and Andraski 2005;Isse et al 1999;Teasdale and Abdul-Baki 1998;Vyn et al 1999). Similar to our results, Isse et al (1999) found that forage radish (Raphanus raphanistrum L.), ryegrass (Lolium multiflorum L.) and red clover (Trifolium pratense L.) did not affect sweet corn shoot or cob N content at harvest.…”

Nitrogen use efficiency and fertiliser fate in a long-term experiment with winter cover crops

“…However, when the N application is reduced, the results are more uncertain. Usually, under suboptimal N fertilisation, a non-response or an increase in yield is reported after legumes (Tonitto et al 2006) and a non-response or a decrease after grasses (Thorup-Kristensen, 1994;Vyn et al, 1999;Quemada et al, 2013). The results of N uptake after cover crops in the literature vary greatly (Thorup-Kristensen et al, 2003).…”