The biophysical and crop yield effects of irrigation and their changes in China’s drylands

Irrigation is critical for food production, especially in arid and semi-arid regions, and it has complex and interactive effects on local climate, evapotranspiration, and crop growth. Here, we used satellite remote sensing data and statistical models to quantify the biophysical effects of irrigation on land surface temperature (LST), evapotranspiration (ET), crop greenness, and crop yield effects and their spatiotemporal changes in China’s drylands. Results show that during 2001–2012, irrigation in China's drylands led to a significant cooling in daytime LST (-0.52 °C), a weak cooling in nighttime LST (-0.14 °C), and increases in ET (+0.16 mm/d), crop greenness (+0.02) and maize yields (+3.4 ton/ha; 55 %) compared with rainfed croplands. The spatial variations of these irrigation effects were in synergy, driven by irrigation water use and climate conditions, with greater effects in the dry regions with higher irrigation intensity. Temporally, the irrigation cooling effects gradually weakened from 2001 to 2020 (0.08 °C), while the enhanced effects on ET (+0.062 mm/d), crop greenness (+0.006) and maize yields (+720 kg/ha) were still increasing. These divergent changes were mainly driven by declined irrigation water use and increased irrigation water productivity due to adopting water-saving irrigation technologies. This study improves our understanding of the irrigation effects and their responses to changing irrigation practices and climate in water-limited regions.