Effects of water stress on nutritional quality of alfalfa in arid and semiarid areas

This study examined the effects of water stress on nutritional quality of alfalfa in arid and semiarid areas, which are under strict controls of water consumption. We conducted a field experiment considering alfalfa under full irrigation conditions (4 200 m3·hm-2), 80% full irrigation (3 360 m3·hm-2), and 60% full irrigation (2 520 m3·hm-2), and measured the stem-leaf ratio and nutritional quality index. We found that throughout the growing season, there were significant differences in the distribution of crude protein, ether extract and crude ash among different cuttings. The size of these differences declined from the first cutting to the third cutting. In leaf-stem ratio, neutral detergent fiber content, and acid detergent fiber content, this trend was reversed. Further analysis showed that in comparison with full irrigation, yield from plants irrigated at 80% increased by 5.10%, and in comparison with 60% full irrigation, yield from plants raised under 80% irrigation increased by 10.60%. Under the same comparisons, crude protein content rose 9.60% and 22.74%, ether extract content rose 3.33% and 7.90%, acid detergent fiber content fell 8.57% and 13.30%, content of neutral detergent fiber fell 6.51% and 11.56%, and crude ash content rose 3.20% and 4.54%. We conclude that 80% full irrigation during the growing season is an optimum level for improving water use efficiency and nutritional quality of alfalfa in arid and semiarid areas.