Modelling the agricultural and environmental consequences of non-uniform irrigation on a maize crop. 2. Nitrogen balance

Irrigation non-uniformity is a key factor in reducing water and N efficienc y and increasing N leaching. This study simulates the impact of non-uniform irrigation on crop growth and associated nitrogen fluxes. Simulations were applied to a travelling gun irrigation system on a maize crop over a 21-ye ar period. Cropping and intercropping periods were analysed for two fertili sation rates (180 and 280 kg N.ha(-1)). The spatial coefficients of variati ons over a period of 21 years were below 37, 8, 25 and 34%, for N uptake, m ineralised N, inorganic N left in the soil at harvest and leached N, respec tively. Simulations with or without reinitialization every year of inorgani c N and water content at sowing gave similar results, except in specific ye ars. Differences between high and low fertilisation treatments showed up es pecially for leaching. Other irrigation and fertilisation strategies should be further analysed to provide more general conclusions.