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

Affected by climate change and elevated atmospheric CO2 levels, the efficacy of agricultural management practices is of particular concern in a hyper-arid area. The effects of future climate change on cotton (Gossypium hirsutum L.) yield and water productivity (WP) were 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 automatic irrigation method based on crop plant available water, factorially combined with four irrigation levels (100 %, 80 %, 60 %, and 50 %). Weather data was obtained from ten general circulation models, and two Shared Socioeconomic Pathways were tested. Deficit irrigation under climate change showed a simulated decrease in water use and production of cotton compared to the baseline (1960-2019). For the 2061-2080 period, mean simulated seed cotton yields were 4.43, 4.44, 3.95 and 3.47 Mg ha-1 (vs. baseline: 4.65, 4.40, 3.58, 2.63 Mg ha- 1) with the 100 %, 80 %, 60 % and 50 % irrigation levels. A 3.4 %-28.6 % of decrease (vs. baseline) in seed cotton yield was found under SSP585 scenario in 2081-2100. The 80 %PAW-based irrigation provided the highest WP of 12.8 kg m-3 and 8.4 kg m-3 for 2061-2080 and 2081-2100, respectively, comparing to the baseline WP of 0.82 kg m-3. Under SSP585 for 2081-2100, the simulated WP declined from 0.19 kg m-3 at 100 % irrigation levels to 0.04 kg m-3 at 50 % irrigation levels. These projections suggests that adequate irrigation is the key to ensure cotton production and moderate deficit irrigation can be applied to mitigate the negative impacts of climate change on cotton yield in a hyper-arid area.