STRATEGIES FOR LIMITED IRRIGATIONS OF MAIZE IN SOUTHWESTERN FRANCE - A MODELING APPROACH

Techniques are needed to determine optimum management strategies for u se of limited irrigation water in southwestern France. The objective o f this study was to use the Erosion-Productivity Impact Calculator (EP IC) model to maximize maize (Zea mays L.) yield using a total of 1000 m(3) irrigation ha(-1) y(-1). In order to conduct the study, the EPIC model was modified to simulate more accurately the effects of drought stress on biomass production and harvest index of maize. Field data fr om a five-year experiment near Toulouse, France, were used for model c alibration and validation. Simulations of 20 climatic years were condu cted for each of three characteristic soils and six irrigation managem ent strategies. Simulated increases in yields and net economic return due to limited irrigation differed among years, soils, and irrigation strategies. The simulated results agreed well with the known effects o f drought stress during critical crop growth periods, indicating that EPIC can be used to determine optimal strategies for limited irrigatio n of maize in southwestern France. Since EPIC can also simulate multip le crops grown in rotation, further research should be conducted to de termine if the model can be used to make more complex recommendations involving multiple crops and spatial distribution of irrigation resour ces.