Modelling of berseem (Trifolium Alexandrinum L.) growth and biomass yield under different levels of water stress in Tadla, Morocco.

This work compares the performance of PILOTE, an operative crop model developed by IRSTA Montpellier France, with that of well established model, CropSyst, in simulating berseem (Trifolium Alexandrinum L.) growth under different water regimes in the semi-arid climate of Tadla (Morocco). Both based on Beer’s law via the intercepted potential active radiation (IPAR) regarding dry matter accumulation, the models differ in the level of complexity describing crop development, biomass growth, root water uptake principle and consequently, in the number of input parameters. The models were calibrated on an unstressed irrigation treatment in 2009/10, and were validated on other stressed and unstressed treatments in 2009/10 and 2010/11. Although PILOTE required fewer input parameters and data than CropSyst, it performed similarly better when simulating both biomass and soil water balance. The use of different numbers of parameters and crop growth modules by the tested models did not influence substantially the simulation results. Therefore, for management purposes and in conditions of limited input information, the use of simpler models should be encouraged.