Abstract
Cover crops can reduce leaching and erosion, introduce variability into crop rotations and fix nitrogen (N) for use by the main crops. In Finland, undersowing is a suitable method for establishing cover crops in cereals. The effect of annual undersowing on soil nitrate N was studied at two sites. Red clover (Trifolium pratense L.), white clover (Trifolium repens L.), a mixture of red clover and meadow fescue (Festuca pratensis Huds.), and westerwold ryegrass (Lolium multiflorum Lam. var. westerwoldicum) were undersown in spring cereals during six successive seasons, and a pure stand of cereal was grown in two years after that. In all years, the soil nitrate N was measured in late autumn, and in addition in different times of the season in last four years. The effect of undersowing on soil NO3-N content was generally low, but in one season when conditions favoured high N leaching, westerwold ryegrass decreased soil NO3-N. The negligible increase of N leaching risk in connection with undersowing clovers, associated with late autumn ploughing, supports the use of clovers to increase the cereal grain yield. The highest levels of soil NO3-N were recorded at sowing in spring irrespective of whether a crop was undersown or not. NO3-N contents were higher in sandy soil than in silt. Undersowing can be done annually in cereal cultivation either to fix or catch N. No cumulative effects on soil nitrate N were associated with undersowing after six years.;
Highlights
Introduction the release of cover cropN was studied
Risk for N leaching can be decreased with undersowing with grasses, effect of west
Italian ryegrass, which grows more reliably in autumn than westerwold ryegrass, was shown by Lemola et al (2000) to reduce N leaching by 27 to 68% depending on soil type
Summary
Introduction the release of cover cropN was studied. For instance, the net N mineralization can occur too late to be of use to the succeeding crop (ThorupKristensen 1996). The net N mineralization can occur too late to be of use to the succeeding crop (ThorupKristensen 1996). The effects of cover crops from different years on soil. N can be mixed, because the release of N from plant material takes longer than one growing season (Jensen 1992). N fertilisation and its effect on the growth of both the main and undersown crop are influencing when the effect of undersown crops on soil N is measured. Soil type can greatly affect N leaching. Kolenbrander (1969) reported low leaching from clayey soil and high leaching from sandy soils
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