Abstract:

This research explored the effects of water and fertilizer and their interaction on the growth and nutritional quality of alfalfa under drip irrigation. The design incorporated four water supply treatments （W₁， W₂， W₃， W_4，） and five fertilizer treatments （F₁， F₂， F₃， F₄， F₅）， and used a split-plot ANOVA design to analyze the alfalfa growth rate， hay yield and nutritional quality under the various combinations of water and fertilizer application. It was found that optimal irrigation and fertilization significantly increased the alfalfa plant height， growth rate and number of branches， enhanced hay yield and improved the nutrient status. Increasing the amount of irrigation decreased the irrigation water use efficiency， and the yield response to fertilizer increments increased initially and then decreased with successive water increments. Similarly， increasing the amount of fertilizer applied decreased the yield response to further fertilizer increments， while the irrigation water use efficiency increased initially and then decreased with successive fertilizer increments. Based on the Grey correlation and a ‘fuzzy similarity priority ratio evaluation’ analysis， it was concluded that the plant height， growth rate， and number of secondary branches contributed strongly to hay yield， and the number of primary branches and leaf to stem ratio contributed weakly to hay yield. The W₃F₂ combination of water and fertilizer gave the highest hay yield （19832 kg·ha^-1） and protein content （19.27%）， and also a comparatively high irrigation water use efficiency （3.8 kg DM·m^-3 water） and fertilizer partial productivity （146.9 kg DM·kg^-1）. A regression optimization model showed that the optimal range of water and fertilizer for alfalfa production under drip irrigation was an irrigation amount of 6000-6500 m³·ha^-1， and a fertilizer application rate of 250-320 kg·ha^-1.

Key words: alfalfa, drip irrigation, water and fertilizer coupling, hay yield, nutritional quality