Effects of partial root-zone drying on alfalfa growth, yield and quality under subsurface drip irrigation

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.