Influence of grazing intensity on soil organic matter and available nutrition of meadow steppe in Zhaosu

The influence of grazing intensity including light grazing, moderate grazing and heavy grazing on soil organic matter, soil available nitrogen, soil available phosphorus and soil available potassium in Zhaosu meadow steppe by plot grazing experiment under short grazing period was studied. Results showed that the aboveground biomass of grassland declined along with the increasing of grazing intensity, and there were no significant difference among different grazing intensities (P0.05). The content of soil organic matter, available nitrogen, available phosphorus and available potassium of 0-10, 10-20, 20-30 cm were not significantly different among different grazing intensities at the same year (P0.05). Compared with no grazing, soil nutrition content of 0-30cm appeared a trend of increasing or decreasing in a certain degree after grazing. And,different indexes had different change trend, which embodied annual changes. Correlation analysis suggested that there was no significant correlation between grazing intensities on soil organic matter, soil available nitrogen, soil available phosphorus, and soil available potassium of 0-30 cm (P0.05). Response of these soil nutrition to grazing intensities was different. Whether grazing or not, the content of soil organic matter, soil available nitrogen, soil available phosphorus, soil available potassium all decreased with the increasing of soil depth.