Abstract:

To study the soil nutrients in the middle and upper reaches of the Niyang river basin of Tibet and explore the spatial variability and distribution characteristics of soil nutrients, 216 soil samples (0-10, 10-20 and 20-30 cm) were taken by standard sampling method in the cultivated land, grass land and forest land, and the content of total nitrogen, alkali-hydrolyzed nitrogen, total potassium, available potassium, total phosphorus, available phosphorus and soil organic matter were determined. The results show that the content of soil organic matter, total nitrogen and alkaline hydrolysis nitrogen in the study area have an order of forest land> grass land>cultivated land, and there are significant differences among the three (P<0.05). There is no significant difference in total potassium content between grass land and forest land, and the available potassium content is forest land> grass land>cultivated land. Under different land use types, the distribution of total nutrients and available nutrients in the soil show certain surface clustering, the content of total nutrients and available nutrients in the soil at the depth of 0-10 cm is significantly higher than that of 10-20 cm and 20-30 cm and the three have significant differences (P<0.05). The average content of alkaly-hydrolyzed nitrogen in the forestland is the highest and that of cultivated land is the lowest in the study area. The average content of available phosphorus in cultivated land (19.47 mg/kg) is significantly higher than that in grass land (5.73 mg/kg) and forest land (5.19 mg/kg). In conclusion, long-term vegetation restoration can improve soil quality in the upper and middle reaches of Niyang river basin, and the study could provide basic support for improving the soil effect in the area.

Key words: soil nutrients, land use type, soil quality, available nutrient, the middle and upper reaches of Niyang river basin, Tibet