Effects of grassland vegetation nutrient and soil physical and chemical properties under grazing pressures

This study investigated the changes of crude protein and crude fat, soil bulk density and soil organic matter under different grazing pressures in steppe desert grassland of northern Tianshan Mountains. The results showed: 1) for 0 sheep·ha-1 treatment, plant crude protein and crude fat decreased after grazing season compared to the beginning of grazing season in spring and autumn. Consistent with this, a similar trend was observed in autumn season for 1.13 and 1.95 sheep·ha-1 treatment; however, in spring season, the crude protein and crude fat increased after grazing in spring for 1.13 and 1.95 sheep·ha-1 treatment. 2) soil bulk density are relative stable for all treatments before and after grazing season; soil organic matter showed a down trend after spring grazing for 1.95 sheep·ha-1, and a slight decrease was observed in terms of each soil layer organic matter for 1.13 and 1.95 sheep·ha-1 after autumn grazing. There was a significant difference between 1.95 and 0 and 1.13 sheep·ha-1 in terms of soil organic matter after spring grazing(P＜0.01). 3) From the change of crude protein and crude fat contents, soil bulk density and soil organic matter content, 1.13 sheep·ha-1 is more reasonable grazing intensity.