Potential deficit irrigation adaptation strategies under climate change for sustaining cotton production in hyper–arid areas

Abstract Affected by climate change and elevated atmospheric CO2 levels, the efficacy of agricultural management practices is of particular concern in a hyper–arid area. Herein, the effects of future climate change on cotton (Gossypium hirsutum L.) yield and water use efficiency (WUE) was assessed under deficit irrigation strategies in China’s southern Xinjiang region. A previously calibrated and validated RZWQM2 model simulated cotton production for two time periods ranging between 2061–2080 and 2081–2100, under two automatic irrigation methods [crop evapotranspiration (ET–based) and plant available water (PAW–based)], factorially combined with four irrigation levels (100%, 80%, 60%, and 50%). Weather information was obtained from ten general circulation models, and three Shared Socioeconomic Pathways were tested. Simulation results showed that the irrigation strategy had a greater impact than climatic change on water use and crop production of cotton. Under climate change, both ET– and PAW–based irrigation methods with deficit irrigation showed a simulated decrease in water use and production of cotton compared to the baseline (1960–2019). Under future climate conditions, for a given irrigation level, PAW–based irrigation led to 35.3 mm–135 mm (7.4–53.9%) greater water use for cotton than did ET–based irrigation. For the 2061–2080 period, mean simulated seed cotton yields were 4.47, 3.69, 2.29 and 1.63 Mg ha–1 with the 100%, 80%, 60% and 50% ET–based irrigation protocols, respectively, and 4.46, 4.41, 3.85 and 3.34 Mg ha–1 with the equivalent PAW–based irrigation protocols. Similar yields were simulated for the 2081–2100 period. In addition, the 80% PAW–based or 100% ET–based irrigation protocols under future climate change provided the greatest cotton WUE in southern Xinjiang.