Optimal sowing dates for major crops in India under climate change

Agriculture plays a pivotal role in supporting the socioeconomic situation of millions of farmers in India, which is increasingly coming under threat due to climate change. In particular, the future changes in rainfall patterns has the potential to directly affect the irrigation water demands, thereby impacting water consumption, agricultural productivity, and influencing food security. For instance, the optimal sowing dates for crops may change according to the altered rainfall patterns. With this motivation, we studied the impacts of shifts in sowing periods in order to identify the optimal sowing dates for a particular crop. First, we collected daily temperature and rainfall data for India at a resolution of 0.25^o from different GCM models (EC-Earth 3 and EC-Earth 3 veg) under different SSP scenarios (SSP 126, SSP 245, SSP370, SSP585). Also, region-wise agricultural data such as crop acreage and sowing dates were collected for seven major crops - paddy, wheat, maize, groundnut, sugarcane, red gram, black gram, and soybean. Subsequently, we estimated the reference evapotranspiration using the modified Penman-Monteith method. The estimated reference evapotranspiration and rainfall data were incorporated into FAO’s CROPWAT model to calculate the irrigation water requirements (IWR) of the selected crops. The optimal IWR for each crop was selected by varying the sowing dates at fifteen-day intervals across the year (twenty-four dates for the year). Preliminary results indicate that there is considerable scope for water savings by shifting the sowing dates of staple crops to account for climate change impacts. These strategies may become vital for policymakers in the coming decades to reduce the stresses on water without endangering food security. Indeed, such strategies require the cooperation of various stakeholders for better implementation at multiple scales.