Studies on the characteristics of soil fertility and relationshipamong nutritive factors in alpine grassland soil of Qilian mountains

Abstrcat Studies in this paper showed that the nutrient factors varied very much among soil types in Qilian mountains and the studied 8 soil types could be grouped into two groups (Group A and B) according to nutritive factors. Group A included subalpine shrub soil, alpine meadow soil, alpine chernozem and subalpine meadow soil. The organic matter content (OMC) in this group was above 14%. Group B included alpine chestnut soil, alpine brown soil, subalpine steppe soil and alpine steppe soil and their OMC were below 4%. Among 8 soil types, the subalpine meadow soil had the highest OMC (19.61%) and alpine steppe soil had the lowest (1.77%). The pH value of 8 soil varied from 7.2 to 8.4. The variance trend of Cation Exchange Capacity (CEC) was similar with the OMC. The highest was subalpine meadow soil (65.61 m·e·/100g) and the lowest was alpine steppe (10.64 m·e·/100g). The characteristic of total nutrients was low phosphorus, high nitrogen and relative rich potash. However, the available nutrients were characterized with low available phosphorus. It was slightly higher in group A (between 13.2×10-6 and 28.2×10-6) and quite low in Group B (between 1.8×10-6 and 4.9×10-6). All nutritive factors had significant relationship each other except total potash, available potash and pH value. Especially the relationship coefficients of OMC and CEC with other factors were above 0.844. The nutritive condition suggests that phosphorus should be applied during grassland improvement and artificial grassland establishment. For alpine steppe soil and subalpine grassland soil, nitrogen fertilizer or legume should be used at the same time.