Abstract:

In order to discuss the soil fertility changes rule of alfalfa grassland in alfalfa fields in hilly loess region of south Ningxia, the factor analysis, correlation analysis, grey correlation, and variation coefficient method were used to calculate the weights of several fertility factors in this paper. The results showed that the order of weight on soil fertility factors was organic matter > available N > total N > Soil pH > available P ≈ total P > available K, the weight of organic matter, available N, total N and Soil pH were higher, which could be taken as the key fertility indicators in alfalfa fields .The fertility index calculated by using Nemoro comprehensive index method in arid alfalfa fields was from 0.549 to 0.873, which was an average level. After crops were replaced by alfalfa, soil and water erosion were obviously controlled, and the differences of fertility indices between different slope positions gradually reduced. The order of comprehensive fertility indices of alfalfa fields with different ages was: 7 years > 3 years > 19 years.