Effects of Planting Tea Trees and Citrus Trees on Soil Fertility and Soil and Water Loss in the Red Soil Hilly Region

In order to explore the effect of economic forest planting on the soil fertility and soil and water conservation, the garden plots planted with tea trees and citrus trees for 10 years in the red soil hilly area of Changshan County in Zhejiang Province were taken as the object, and the bare land was taken as the control group. Then, the orientation research on the amount of soil and water loss was carried out, and the volume weight of soil, soil porosity, rapidly available nitrogen, phosphorus and potassium, and carbon and nitrogen contents in different aggregate components in 0−10 cm soil layer were sampled and analyzed. The results showed that: after planting tea trees and citrus trees for 10 years, the volume weight of soil decreased significantly (P＜0.05), and the soil porosity, field water-holding capacity, and the contents of organic carbon, available phosphorus, rapidly available potassium and alkaline hydrolysis nitrogen increased significantly (P＜0.05). The content of organic carbon in soil macro-aggregates was in the order of citrus orchard > tea garden > bare land. The contents of organic carbon and nitrogen in soil aggregates, micro-aggregates and soil silt particles were in the order of tea garden > citrus orchard > bare land, and the differences among different treatments were significant (P＜0.05). The contents of organic carbon and nitrogen in soil clay in tea garden were significantly higher than those in citrus orchard and bare land (P＜0.05). Compared with the bare land, the depth of annual runoff in the citrus orchard and tea garden was significantly reduced by 87.66 % and 92.25 % (P＜0.05), and the amount of annual soil loss was significantly reduced by 95.93 % and 98.78 % (P＜0.05). The depth of annual runoff and the amount of annual soil loss in the experimental area had extremely significant or significant negative correlations with soil organic carbon, total porosity and field water-holding capacity (P＜0.01, P＜0.05), while had high positive correlation with the volume weight of soil (P＜0.05). In summary, the planting of tea trees and citrus trees was conducive to improving the soil fertility and reducing the soil and water loss, and the effect of planting tea trees was better than that of citrus trees.