Application of nitrogen cycle modelling to land use policy issues: nitrate leaching from winter and spring cereal cropping

Abstract

Under some circumstances nitrate leaching may be more serious under winter cereals than under spring cereals. We have evaluated the factors controlling the relative efficiency of N use by winter and spring cereals under cool, moist climatic conditions using simulation modelling, field trials data and literature survey. The most important factors which may cause winter cereals to be more leaky are larger fertiliser application rates for winter cereals, not fully compensated by larger N offtake; smaller potential for post-harvest denitrification of excess N from cultivated land sown to winter cereals than from uncultivated stubble land; and greater accumulation of unused mineralised N because of earlier harvesting of winter cereals. Simulation modelling over 3 years under local weather conditions showed mean annual Nitrate-N concentrations in drainage water were 5 mg L−1 higher on a sandy loam soil, and 3 mg L−1 higher on a clay loam soil with winter instead of spring cereals at recommended fertiliser rates.