Abstract: A field experiment with five chicken-grazing intensities (0 feather·200 m^-2, CK; 10 feathers·200 m^-2, D₁; 10 feathers·400 m^-2, D₂; 10 feathers·600 m^-2, D₃; and 10 feathers·800 m^-2, D₄) was conducted in the Keerqin Sandy Land of China to study the effects of the grazing intensity and sampling time on the soil inorganic nitrogen concentration, potential net nitrogen mineralization and nitrification rates, and microbial biomass in sandy grassland. Compared with CK, treatments D₁ and D₂ increased the soil potential net nitrogen mineralization and nitrification rates in August and October significantly, while treatments D₃ and D₄ had little effects on the soil nitrate nitrogen concentration and the soil potential net nitrogen mineralization and nitrification rates. Chickengrazing increased the soil nitrate nitrogen concentration and the soil potential net nitrogen mineralization and nitrification rates significantly, but less affected the soil ammonium nitrogen concentration. Sampling time had significant effects on the soil inorganic nitrogen concentration and the soil potential net nitrogen mineralization and nitrification rates, but the effects of the interaction between grazing intensity and sampling time were not significant. Chickengrazing had little effects on the soil microbial biomass C, N, and C/N. In conclusion, chicken-grazing could enhance the soil nitrogen supplying capability, which had an uptrend with the increase of grazing intensity. In this study, the optimum grazing intensity was 250-500 feathers·hm^-2.

Key words: genetic structure., enzootic, ISSR, Isaria cicadae