Effects Of Raiseing Chichens Under The Plantation In The Hilly Region Of Sichuan Basin On Soil Carbon Pools

In order to study the effect of different chicken density (160/mu,80/mu,40/mu and0/mu) on soil carbon components and soil nutrients, we studied breeding chickens in citrus forest of western hills of Sichuan province in this paper and discussed the relationship of soil carbon components and carbon pool management index with soil nutrients. The main results are the followings.(1) The single fruit weight and productivity of citrus, soil clay content, natural moisture content and the content of total nitrogen, available nitrogen, available phosphorus and available K in chicken area of citrus forest were all higher in than those in none-chicken area and increased with the increase of chicken density, and all these indexes in0～20cm soil layer were higher than those in20-40cm soil layer. On the contrary, soil bulk density in chicken area was higher than that in none-chicken area and increased with the decrease of chicken density. Also soil bulk density in upper layer of soil was lower than underlying soil layer. All these indicated that,when chicken density was at the range of160/mu, the increase of chicken density had an important role and meaning on improving soil water-holding and water supply capacity, physical and chemical properties of soil and soil capacity to supply nutrient.(2) The content of soil organic carbon, microbial biomass carbon and its ratio in soil organic carbon, water soluble organic carbon and its ratio in soil organic carbon, active organic carbon and its ratio in soil organic C and un-active C in chicken area were all higher than in non-chicken area, and they all increased with the increase of chicken density and were higher in upper layer of soil than in underlying soil layer. Compared with non-chicken control, soil organic carbon in0-40cm soil layer of160/mu,80/mu and40/mu was increased46.6～50.6%,19.3～30.4%and8.0～22.9%, respectively. Soil organic carbon storage and carbon sequestration capacity in different soil layers were all increased with the increase of chicken density, which meant, when chicken density was at the range of160/mu, the increase of chicken density will contribute to increasing soil organic carbon and its content of components and had a significant effect on increasing soil carbon storage, carbon sequestration capacity and mitigating the global change in climate.(3) Soil carbon pool index (CPI), carbon pool activity (L), activity index (LI) and carbon pool management index (CM1) in chicken area were all higher than in none-chicken area and increased with the increase of chicken density, and all these indexes were higher in in upper layer of soil than in underlying soil layer. Correlation analysis showed that all carbon fractions and carbon pool management index were positively correlated with single fruit weight and productivity of citrus and chemical and physical properties of soil and also soil carbon pool management index was positively correlated with the content of all carbon fractions. The results indicated that soil carbon pool management index had a close relationship with fruit size and yield, physical and chemical properties of soil and the content of all carbon fractions. Therefore through the study of soil carbon pool management index we can forecast the effect of breeding chicken on the change of orchard soil fertility and fruit productivity. The results provided reference for developing forest farming and setting appropriate chicken density to improve soil fertility and soil carbon-sink function.