Spatial Variation Of Soil Nutrient And Its Influencing Factors In Dagang River Watershed

Based on the mesh point sampling method, this paper investigated soil nutrients and vegetation coverage in Dagang River watershed. Spatial variation of soil nutrient and its influencing factors was studied so as to get a better understanding of the soil nutrient distribution in the small watershed, rational planning of land use and development of precision agriculture. The main results of this study were as follows:(1) The spatial variation of soil organic matter (SOM) is most volatile in all test soil nutrient, followed by ammonium nitrogen (NH4+-N) and total phosphorus (TP) is the most stable. The soil nutrient space mutation analysis shows that SOM tested by two different method (Oil bath and the loss on ignition method) have very good consistency. The correlation analysis showed that SOM reached a significant level or very significant level with total nitrogen (TN) and nitrate nitrogen (N03--N), soil NH4+-N, NO3--N and TN were also significant or very significant. Spatial variation of soil nutrient include SOM, TN, NH4+-N, NO3--N and TP were closely related to soil land use.(2) The soil moisture content affects the spatial distribution of soil nutrients. Higher soil moisture content is conducive to the plants to absorb nutrients and growth bigger, thus, promote the improvement of soil organic matter content. Terrain, especially the elevation have a high impact on the spatial distribution of soil nutrients, it is because land use and vegetation distribution was more susceptible to the influence of elevation. SOM and soil TN was positively correlated with the elevation and the difference reached a significant level.(3) Nitrogen and phosphorus content and ratio of N to P various in different plant leaves indicates different amounts of needs for soil nitrogen and phosphorus in those plants. Ratio of N to P in leaves of bamboo, tea and Masson pine have a significant or very significant negative correlation with leaf P content. The ratio of leaf N to P in tea has a significantly positive correlation with TN in soils near the plant but not significant with soil TP. Ratio of N to P in leaves of bamboo and Masson pine has no significant correlation with TN and TP in soil near them.(4) Land use had a greater influence on soil physical properties, especially the surface soil. Within the rice paddy field, tea plantation, forest land and bush land, soil water content in0-20cm soil layer was in the order of paddy field>bush land>forest land>tea garden; Compared to0-20cm layer,20-40cm layer showed a different variation in the order of bush land> forest land> paddy field> tea plantation. The soil bulk density of0-20cm layer and20～40cm layer have the same change in the order of paddy field> bush land> tea garden> forest land. The bulk density of forest land under the four land use is minimal, which indicates that the soil loose aperture and has the best soil permeability amoung the forest land Paddy field, tea garden etc cultivated soil.(5) Different land use cause significant differences in soil nutrients distribution. pH value in paddy field, tea plantation, forest land and bush land was5.58、4.53、5.24、5.42respectively. SOM, TN and available N was in the order of bush land>forest land>tea garden>paddy field while available P showed a opposite order. The ratio of N to P in plant leaves rank by forest land>bush land>tea garden>paddy field.(6) Soil nutrient content are affected with parent material, topography, climate, vegetation coverage and other natural factors and human interference factors. In regions with the same parent material and climatic condition soil nutrient mainly affect by human activities. Spatial variation of soil nutrient under different land use has significant differences. As nitrogen level of input to the general improvement, we should pay attention to the carbon return level, promoting the straw returned and organic fertilizer input so as to maintain soil carbon and nitrogen balance.