Can farmers use maize earliness choice and sowing dates to cope with future water scarcity? A modelling approach applied to south-western France

International audience

إنجليزي. To sustain food production in the future, the agricultural sector must adapt to climate change through agronomic means. In the Midi-Pyrenees (south-western France), maize is the main irrigated crop, and increasing pressure on water resources challenges the appropriateness of this crop in the region. In this study we evaluated the impact of temperature and precipitation changes on the sowing and harvesting period of maize and, consequently, on the suitability of cultivar earliness to this sowing-harvest window in the future. Next, we quantified the yield and irrigation requirements of three earliness choices (early, medium and late) for the appropriate sowing-harvest window. We ran three simulation models with climate-change scenarios. The first (a sowing model) predicts the days suitable for sowing maize, the second (MODERATO) predicts yield and irrigation requirements for all suitable sowing days, and the third (a harvest model) predicts the days suitable for harvesting. We ran these models with a simulated weather data series covering the reference period (1971-2000) and two future periods (2021-2050 and 2071-2100) for the study area. We also calculated climatic and agronomic indices to understand changes in maize sowing days, the maize growing period and suitable earliness choice due to climate change for the two future periods compared to the reference period. The results showed an increase in thermal time and decrease in rainfall in the future that will influence maize earliness choice, growing period, yield and irrigation requirements. The trade-off between farmers' maize earliness choices and suitable maize growing periods will increase in the future. Late-earliness maize cultivars can be cultivated in the future; however, the associated irrigation requirements also will be higher. Farmers need to cope with climate-induced water scarcity in the future by selecting a suitable sowing date, maize earliness and soil type to cultivate maize.