中文摘要：

依托陇中黄土高原旱作农田已实施13a的保护性耕作试验，研究传统耕作、免耕、传统耕作秸秆还田、免耕秸秆覆盖、传统耕作地膜覆盖和免耕地膜覆盖6种耕作措施下土壤全磷及磷组分动态变化特征。结果表明：试验期各处理土壤全磷和总无机磷均逐年增长；两个秸秆还田处理总有机磷逐年增长，免耕地膜覆盖和免耕处理总体增长，传统耕作和传统耕作地膜覆盖处理相对稳定；各无机磷组分均总体增长，其中氢氧化钠提取态无机磷、水溶态无机磷和碳酸氢钠提取态无机磷涨幅较大，平均涨幅分别为253．6％、128．6％和66．9％；保护性耕作可不同程度地提高水溶态无机磷、碳酸氢钠提取态无机磷和氢氧化钠提取态无机磷含量，相同覆盖条件下免耕较传统耕作效果明显，尤其免耕秸秆覆盖处理最明显；耕作方式对浓盐酸提取态无机磷和残留磷的影响不明显；保护性耕作可提高碳酸氢钠提取态有机磷和氢氧化钠提取态有机磷含量，两个秸秆还田处理最明显，两处理也可提高浓盐酸提取态有机磷含量，但免耕、传统耕作地膜覆盖和免耕地膜覆盖处理下该组分含量降低。综上，采取保护性耕作可适当减少磷肥用量，保护性耕作尤其是免耕秸秆覆盖方式值得在该区推广。

英文摘要：

【Objective】The Loess Plateau in Central Gansu is one of the most seriously eroded regions in China. In this area the soil is generally in lack of phosphorus, and the conventional tillage pattern prevailing in the region exacerbates the loss of phosphorus and other soil nutrients. Therefore, it is urgent to address the problem by improving farmland management and hence to uplift utilization efficiency of soil phosphorus. This study attempts to characterize dynamic changes of soil total phosphorus and phosphorus fractions in the soil under six different tillage patterns, so as to reveal mechanisms of the six tillage patterns affecting soil phosphorus, and provide a theoretical basis for remolding the original tillage pattern or establishing a new sustainable tillage pattern.【Method】For this study, a 13-year-long field experiment on tillage has been carried out in an upland farm on the Loess Plateau in Central Gansu. The experiment is designed to have six different tillage patterns, that is, conventional tillage （T）, no-tillage （NT）, conventional tillage with straw incorporation （TS）, no-tillage with straw mulching （NTS）, conventional tillage with plastic mulching （TP）, and no-tillage with plastic mulching （NTP）. For in-lab analysis, Tiessen’s modified Hedley method was used for fractionation of soil phosphorus. Six extractants were used sequentially from weak to strong in capacity to extract nine fractions of phosphorus, that is, Resin-Pi, NaHCO3-Pi, NaHCO3-Po, NaOH-Pi, NaOH-Po, D.HCl-Pi, C.HCl-Pi, C.HCl-Po and Residual-P.【Result】Results show： （1）During the experiment, soil total phosphorus in all the treatments increased year by year, with a rate ranging from 8.1% to 15.6%, and in terms of soil phosphorus increase rate, the six treatments exhibited an order of NTS〉TS〉NTP≈NT≈T≈TP. Total inorganic phosphorus also showed an increasing trend in all the treatments. In Treatments NTS and TS, total organic phosphorus increased the fastest or by48.7% and 46.0%, respect