黄土高原轮作系统苜蓿土壤磷素变化特征

在长期定位试验的基础上，分析黄土高原旱地轮作系统中苜蓿（Medicago sativa）不同生长年份土壤的无机磷、有机磷形态及微生物磷的变化特征，以期为农牧区牧草有效磷素合理利用及区域管理提供依据。结果表明：种植苜蓿的土壤全磷含量与苜蓿种植年份成反比，连续种植苜蓿年份越长，土壤全磷和速效磷的含量越小。苜蓿土壤中无机磷组分以Ca-P为主，占无机磷总量的74.0%～80.0%，且Ca₁₀-P > Ca₈-P > Ca₂-P。有机磷占全磷总量的23.2%～25.4%，土壤有机磷以中活性有机磷为主，占有机磷总量的78.3%～79.5%。苜蓿的种植年份越长，土壤微生物磷含量越低。土壤微生物磷与土壤全磷、速效磷成极显著相关，故土壤微生物磷可作为土壤供磷能力的指标。

Soil Phosphorus Variation of Alfalfa Rotation System in the Loess Plateau

In this paper, the soil inorganic phosphorus, organic phosphorus, and microbial phosphorus variations of alfalfa rotation system were studied under dryland in different growth years to provide a reasonable basis for the effective utilization of phosphorus and regional management in farm and pastoral areas. The results show that and the total soil phosphorus content of planting alfalfa is inversely proportional to the planting years. The contents of soil total phosphorus and available phosphorus decrease with the successive planting years of alfalfa increasing. Soil inorganic phosphorus fractions are mainly in Ca-P based, accounted for the 74.0%～80.0% of total inorganic phosphorus, and Ca₁₀-P > Ca₈-P > Ca₂-P. Organic phosphorus are the 23.2%～25.4% of total P, soil organic phosphorus in the mid-active organic phosphorus-based, about 78.3%～79.5% in total phosphorus. The contents of soil microbial phosphorus decrease with the planting years of alfalfa increasing. There are significant correlation between soil microbial phosphorus and total soil phosphorus, available phosphorus. Therefore, soil microbial phosphorus can be used as an indicator for evaluating the supply capacity of soil phosphorus.