Scenario analysis for cereal management in water-limited conditions by the means of a crop simulation model (STICS)

Crop simulation models are frequently used to evaluate the impacts of water resources (soil, weather and irrigation) on crop production and the environment. This study illustrates the possibilities offered by STICS 4.0 in water-limited environments. Numerical experiments were carried out on winter wheat in order to evaluate drought escape and crop rationing in 3 climatic environments: Avignon, Meknes (Morocco) and Toulouse. The Passioura [33] framework which disaggregates grain yield of cereals into 3 terms: water transpired, transpiration efficiency and the harvest index, was used to analyze the simulation results. Interactions between cultivar earliness and water supply were shown for yield: early-maturing genotypes yielded more in semi-arid conditions because of terminal stress; where intermittent stress was observed (as in Toulouse), no stable ranking was observed between cultivars differing by the date of anthesis. The contribution of soil evaporation to total water use was reduced by rapid canopy closure (fast-growing cultivar and high plant density). On the other hand, water stress during grain filling was more frequent with excessive plant density. Crop management systems resulting from different combinations of cultivar earliness, plant density and supplemental irrigation were simulated: a drought-escaping strategy (early genotype) and crop rationing (low plant density) were suggested under rainfed (semi-arid) conditions. With irrigation or under wetter conditions, yield should be improved by maximizing early canopy closure (high density) and lengthening the growing season period (late genotype). This simulation exercise contributed to the qualitative evaluation of the STICS model for water-limited agriculture.