Abstract Water shortage is the most critical constraint for alfalfa (Medicago sativa L.) hay production in the arid areas of Northwest China. In this study, we evaluated the effectiveness of partial root-zone drying (PRD) with subsurface drip irrigation (SDI) for alfalfa and compared it with conventional subsurface drip irrigation (CI). Field plot tests were conducted in 2017 and 2018 with three irrigation treatments under partial root-zone drying SDI system. Conventional SDI systems were used as the control. The irrigation quotas were 10 mm, 20 mm, and 30 mm per week for PRD1, PRD2, and PRD3, respectively, and that for CI was 30 mm per week. The number of drip irrigations for alfalfa in the whole growing stage were 13 and 19 in 2017 and 2018, respectively. There were three harvests in 2017 and four harvests in 2018. The results showed that the plant height of PRD was 0.4–11.57 cm higher than that of CI under the same irrigation regime. Moreover, PRD decreased the annual hay yield of one-year-old alfalfa, but increased the annual hay yield of two-year-old alfalfa, while in 2018 the annual hay yield increased by 832.27 kg ha−1 as compared to that of CI. Moreover, PRD has marked effect on alfalfa quality under insufficient amounts of water applied (PRD1), with significantly decreased acid detergent fiber by 7.81–27.02% and neutral detergent fiber by 0.25–15.23%, and increased crude protein by 0.59–12.68%, compared with CI. Crop water productivity (WPC) of one-year-old alfalfa under PRD3 in 2017 increased by 4.15–15.33% relative to CI, while WPC of two-year-old alfalfa under PRD2 in 2018 increased by 1.66–44.32% relative to CI. These results suggest that the proposed PRD could be a promising technique for alfalfa production in the arid area of Northwest China, with improved WPC and positive effect on quality characteristics.

中文翻译：

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地下滴灌下部分根区干燥对苜蓿生长、产量和品质的影响

摘要 缺水是西北干旱区苜蓿干草生产的最关键制约因素。在这项研究中，我们评估了部分根区干燥 (PRD) 与地下滴灌 (SDI) 对苜蓿的有效性，并将其与常规地下滴灌 (CI) 进行了比较。2017 年和 2018 年在部分根区干燥 SDI 系统下进行了三种灌溉处理的田间小区试验。传统的 SDI 系统被用作控制。PRD1、PRD2和PRD3的灌溉定额分别为每周10 mm、20 mm和30 mm，CI为每周30 mm。2017年和2018年苜蓿全生育期滴灌次数分别为13次和19次。2017年有3个收获，2018年有4个收获。结果表明，在相同的灌溉制度下，珠三角的株高比CI高0.4-11.57 cm。此外，珠三角地区降低了一年生苜蓿的年干草产量，但增加了二年生苜蓿的年干草产量，而2018年与CI相比，年干草产量增加了832.27 kg ha-1 . 此外，PRD在施水量不足（PRD1）下对苜蓿品质有显着影响，酸性洗涤纤维显着减少7.81-27.02％，中性洗涤纤维显着减少0.25-15.23％，粗蛋白增加0.59-12.68％，与CI相比。2017年PRD3下一年生苜蓿的作物水分生产力（WPC）相对于CI增加了4.15-15.33%，而2018年PRD2下二年生苜蓿的WPC相对于CI增加了1.66-44.32%。