Modelling the agricultural and environmental consequences of non-uniform irrigation on a maize crop. 1. Water balance and yield

Among cropping systems, intensive irrigation probably represents one of the greatest threats to groundwater quality. Irrigation uniformity is a key factor for obtaining more efficient water use by crops and for limiting percolation. The objective of this study is to predict plant growth and water fluxes under non-uniform irrigation conditions. Simulations were applied to a maize crop irrigated with a moving gun. The spatial coefficients of variation for 21 years did not exceed 18, 9, 20, and 36% for irrigation depth, actual evapotranspiration, drainage below the root zone and yield, respectively. Temporal effects due to natural climatic variability dominated, and spatial effects only increased the variance of the fluxes and biomass without strongly modifying the mean patterns. Other sources of variation such as soil type, soil hydrodynamic properties or irrigation strategies must also be analysed to provide more general conclusions.