为了阐明宁南黄土丘陵区旱作苜蓿地土壤肥力的变化特征，采用算术均数赋值法将因子分析法、相关分析法、灰色关联法、变异系数法4种赋权方法相结合，对宁南半干旱黄土丘陵区旱作苜蓿地土壤肥力因子的权重进行计算。土壤肥力因子权重计算结果表明：研究区苜蓿地土壤肥力因子权重排序为有机质>速效氮>全量氮>土壤pH>速效磷≈全量磷>速效钾，土壤有机质、速效氮、全量氮、土壤pH的权重值相对较高，是该区旱作苜蓿地最为关键的肥力指标。利用改进的内梅罗综合指数法得到的苜蓿地土壤综合肥力指数在0.549~0.873之间，土壤肥力水平一般。退耕还林还草旱作苜蓿后，研究区水土流失明显得到控制，不同坡位苜蓿地土壤肥力指数差异逐渐减小；不同旱作年限苜蓿地土壤综合肥力指数排序为：7年生>3年生>19年生。

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.