Intercropping reduces nitrate leaching from under field crops without loss of yield: A modelling study

A model of soil nitrogen dynamics under competing intercrops is described and used to interpret two sets of experimental field data from the literature. In one series of experiments, maize received slurry and mineral nitrogen (N) fertiliser or mineral N alone and was grown either alone or intercropped with undersown grass or with a subsequent rye catch crop during 7 years continuously. In the second system, the model compares field beans intercropped spatially at different densities with winter wheat.The model suggests that undersowing grass between the rows of an established maize crop can reduce concentrations of nitrate in water draining from soils during winter by 15 mg l−1 compared with a conventional catch crop and by more than 20 mg l−1 compared with a fallow soil. The model further suggests that the yield and profitability of mixed stands of commercial crops is inversely related to the residual nitrate at harvest (potential leaching). It is concluded that intercropping may be a useful means to reduce nutrient pollution from farming while maintaining yields.