Abstract: The local poultry breed-Hetian chicken has been grazing mainly under forest for a long time in Changting County. However, the traditional high-density and continuous grazing model under the forest causes damage to the ecological environment. In this paper, the influence of grazing time and grazing model on soil physic-chemical properties and bacterial colonies in forest was studied, and the appropriate grazing time and model of Hetian chicken have been found out. The regular chemical analysis and 16S rDNA sequencing were used to determine the chemical characteristics and microbial diversity of grazing on natural grass (group A) and artificial grass (group B) in the forest land during 3 different grazing time periods. The results show that the soil chemical traits were significantly influenced by grazing methods. The soil SOM, TN, AP, AK, NO₃-N and NH₄⁺-N contents in group B were extreme significantly higher than those in group A. The soil SOM and AK contents in group A and B were gradually increasing. AP contents increased firstly and then decreased, reached the highest point at 60 d, while NO₃-N and NH₄⁺-N contents showed a decreasing trend with the grazing time. Soil microbial diversity indexes Chao1, Shannon and Simpson in group A were greatly influenced by grazing time, while the changes in group B was not obvious. The dominant bacterial colonies of group A were Actinobacteria, Bacteroidetes, Chloroflexi, and Firmicutes, and those of group B were Gemmatimonadetes, Proteobacteria, and Acidobacteria. The results show that grazing on artificial grass under forest for 60 d, the chemical contents are relatively high and the microbial diversity is relatively rich, and the dominant bacterial colonies were Gemmatimonadetes, Proteobacteria and Acidibacteria. The results of this study could provide reference for sustainably maintaining and protecting the soil ecological environment.

Key words: grazing model, grazing time, soil chemical characteristics, soil bacterial diversity