The effect of adapting cultivars on the water use efficiency of dryland maize (Zea mays L.) in northwestern China

Global warming is predicted to have adverse effects on crop productivity and will present an enormous challenge to sustainable development and food security, especially in dryland regions. Prior studies have identified that adapted crop cultivars could effectively act to offset the effects of climate warming; however, the water use of adapted cultivars subject to climate warming is much less understood. We analysed warming trends across the Loess Plateau in north-western China beginning in 1960. There has been significant warming, especially since 1980, with an increase in the growing degree days (GDD, from April to September) of 260–330°C being observed over the past 30 years. If the maize cultivars had remained unchanged, the decreased yield potential would have been 0.39–1.83tha−1 over the last 30 years. Meanwhile, the use of historical maize varieties has resulted in significantly decreased water use efficiency (WUE) across the Loess Plateau. Based on the increase in the GDD in each decade, we suggest planting adapted later-maturing maize cultivars to improve productivity. Compared with historical cultivars, the adapted later-maturing varieties significantly prolonged the maize growing cycle by an average of 27 d, thereby increasing the yield potential by 24.2–64.8% and the WUE by 9.0–38.1% throughout the Loess Plateau. However, the adapted maturing varieties may increase the water consumption (ET), which is the disadvantage for sustainable dryland farming, especially in dry regions. Hence, continuing to develop water-harvesting techniques (e.g., plastic film mulching) will help to offset the decreasing rainfall and guarantee food security and sustainability in dry regions.