The content of soil Micro-biomass Carbon and Nitrogen of Different Grazing Intensities on Pasture

A test was conducted to determine the content of soil micro-biomass carbon and nitrogen on cultured pastures of northern China's agro-pastoral zone,which are divided into three cites of different grazing intensities:light(6 sheep/hm~2),medium(10 sheep/hm~2),and heavy(13 sheep/hm~2).The result shows that different grazing intensities tend to affect the soil microbial biomass of carbon and nitrogen in similar ways. During the grazing period,the soil microbial biomass of the two elements is higher in pastures of medium grazing intensity,while during the rest-grazing period,they are higher in pastures of light grazing intensity and in the control sites.Following the prolonged grazing and deterioration of the environment,the pasture soil micro-biomass carbon and nitrogen decrease incessantly.Judging from the worsening situation,we suggest the grazing-intensity limit in an arid area should be restricted at 6 sheep per square hectometer.