Abstract:

To investigate the effects of altitude on the yield and nutritional quality of alfalfa （Medicago sativa）， we planted four alfalfa varieties in 12 representative plots in the altitude ranges of 1300-1500 m （H₁）， 900-1100 m （H₂） and 500-700 m （H₃） in the Yili River basin， and monitored their growth. Four alfalfa varieties were included in this experiment， namely Algonquin （A₁）， Magnum Ⅶ（A₂）， WL363HQ （A₃）， and Xinmu 4 （A₄）. After harvest， the alfalfa plants were analyzed to determine the contents of crude protein （CP）， neutral detergent fiber （NDF）， and acid detergent fiber （ADF）， the relative feeding value （RFV）， ether extract （EE）， crude ash （Ash）， total phosphorus content （TP） and soluble sugars content （SSC）， and the field hay yield （HY）. The relationship between HY and nutritional indexes of alfalfa was analyzed， and the altitude and varieties suitable for high quality alfalfa feed production were selected based on the results of principal component analysis and membership function analysis. The results show that the CP， EE， RFV， Ash， and HY of alfalfa gradually increased as the altitude decreased， whereas NDF， ADF， and SSC gradually decreased as the altitude decreased. At the same altitude， the RFV， TP， SSC， and HY were significantly higher for A₃ than for the other three alfalfa varieties， and the NDF and ADF contents were lowest in A₃. Pearson’s correlation analyses showed that the HY of alfalfa was positively correlated with CP， RFV， and TP （P<0.05）， but negatively correlated with NDF and ADF （P<0.01）. The CP was positively correlated with TP， EE， RFV， and SSC （P<0.05）. Based on the results of the principal component and membership function analyses， the best performance was observed in A₃ grown at 500-700 m， followed by A₃ grown at 1300-1500 m， and then A₃ grown at 900-1100 m. In conclusion， the yield and nutritional quality of alfalfa plants grown at lower altitudes were superior to those of alfalfa plants grown at higher altitudes in the Yili River basin. Alfalfa variety WL363HQ， coded A₃ in this research，_{can be recommended as suitable for planting at various altitudes in the Yili River basin.}

Key words: Yili River basin, altitude, alfalfa, hay yield, nutritional quality