The effect of plant communities on main soil nutrition

Soil nutrition of a natural grassland and three field cropped sainfoin, wheat and potato was assayed in the hills and dongas area of Loess Plateau in Anding District, Dingxi City. The results showed that soil water content in the natural grassland in the 0-20 cm soil layer increased by 5.6%21.8% than that of the crop lands (P0.05 or P0.01), Total nitrogen content in the two years sainfoin soil was up to 1 367 mg/kg，which was higher than the 1-years sainfoin soil, and other soil (P0.05). Effective phosphor content varied in different soil but difference did not significant. Organic matter and phosphor in each soil varied with the same trend from April to June and August, however, pH changed very little.