Irrigation plays a fundamental role in sustanining the productivity of agricultural systems in the inland arid area of midwestern China. Deficit irrigation can help to balance yield outcome and water input. Few studies have investigated the impact of deficit irrigation on alfalfa performance, which shows great differences from grain crops in water requirement and management strategy. The study aimed to evaluate the effect of regulated deficit irrigation on forage yield and quality of alfalfa (Medicago sativa). A three year trial was carried out with two irrigation systems (flood irrigation, FI and subsurface drip irrigation, SDI) and seven contrasting regulated irrigation treatments, and alfalfa growth, productivity and water use were measured. Under both irrigation systems, alfalfa forage yield decreased with decreasing irrigation amount under whole stage irrigation, while forage quality improved. However, the performance of alfalfa was different when deficit irrigation was applied at various growth stages. Compared with other deficit irrigation treatments, regulated deficit irrigation at single growth stage usually led to a higher yield. There was an exponential relationship between plant height and forage yield (R² = 0.62 for FI and R² = 0.57 for SDI) and a linear relationship between leaf area index and forage yield (R² = 0.56 for FI and R² = 0.64 for SDI). There was a negative correlation between forage yield and quality, which was closer to some quadratic relationships. Therefore, regulated deficit irrigation can help to achieve an ideal yield (up to 34.9 t/ha) and quality in this area. In the inland arid area of midwestern China, subsurface drip irrigation showed a higher irrigation water use efficiency (13.8–84.4 kg/(ha mm)) than flood irrigation (10.8–66.6 kg/(ha mm)) for alfalfa production. With limited water supply, deficit irrigation at single growth stage usually maintained a higher forage yield compared to slightly stressed irrigation during the whole growth. Deficit irrigation at the branching stage led to more negative effect on forage yield compared to other single stages.

在中西部内陆干旱地区，灌溉在维持农业系统生产力方面发挥着根本作用。亏缺灌溉可以帮助平衡产量和水的输入量。很少有研究调查缺水灌溉对苜蓿性能的影响，这表明谷物作物的需水量和管理策略存在很大差异。这项研究的目的是评估对饲草产量和苜蓿的质量调亏灌溉的影响（紫花苜蓿）。进行了为期三年的试验，使用了两种灌溉系统（洪水灌溉，FI和地下滴灌，SDI）和七种对比调节灌溉处理，并测量了苜蓿的生长，生产力和用水量。在两种灌溉方式下，紫花苜蓿的牧草产量随着全季灌溉量的减少而降低，而牧草质量提高。然而，当在不同的生长阶段进行亏缺灌溉时，苜蓿的表现是不同的。与其他亏水灌溉相比，单生育期的节水灌溉通常可提高产量。株高和草料产量之间存在指数关系（FI和R ^2的R ² = 0.62SDI = 0.57）和叶面积指数与草料产量之间的线性关系（FI和R ^2的R ² = 0.56）对于SDI = 0.64）。牧草产量与质量之间存在负相关关系，接近一些二次关系。因此，调节性缺水灌溉可以帮助该地区实现理想的产量（最高34.9吨/公顷）和质量。在中西部内陆干旱地区，紫花苜蓿生产的地下滴灌显示出更高的灌溉用水效率（13.8–84.4 kg /（ha mm）），而洪水灌溉（10.8–66.6 kg /（ha mm））更高。在供水有限的情况下，与整个生长期间的轻度灌溉相比，单生育期的亏缺灌溉通常保持较高的饲草产量。与其他单一阶段相比，分枝期的亏缺灌溉对牧草产量产生了更多的负面影响。