| Southern red soil hilly region is a serious soil erosion area. It is an emphasis to control soil erosion and agricultural nonpoint source pollution in this area for achieving sustainable agricultural development. According to the above things, in this study, select the persimmon forest slope in water source of Zhejiang Yongkang. Emplaced seven runoff plots on the forest slope, and equipped every plot with a grit chamber to collect sediment water samples. Collect the runoff containing sand water samples regularly. Finish test analysis and data processing of concentration of sediment samples and water samples nutrient substances. The main results are as follows:1. There is a significant hydrological time characteristics of soil erosion and nutrient loss during the test area. Its distribution and amount of precipitation during the loss was significantly synchronization feature. Rainy season in June and typhoon season in August and September is the peak occurred during the testing of soil erosion and nutrient nonpoint source pollution.64.8%soil erosion and about half proportion nutrient loss during the year occurred at this period. TN and TP loss accounted for51.0%and46.4%of the hydrological year. NO3--N and NH4+-N losses were also accounted for49.7%and51.6%in the year. Affected by rainfall characteristics during these two periods, the relationship of sediment concentration is typhoon Season> rainy season> other periods. K and TOC were respectively accounted for60.4%and65.7%in the year.2. Soil erosion and nutrient loss characteristic of different terrain is significantly differences among the crest, convex and concave slope runoff plots. The main characteristics follow the laws of soil erosion and nutrient loss in slope. With the increase in soil erosion slope tended to increase. And the loss of nutrients in the presence of obvious "critical slope laws", the critical gradient exists between10.22°and18.55°. The relationship of losses on TN and NO3--N is crest> concave>convex. And the relationship of losses on NH4+-N and TP is concave> crest>convex. The relationship of losses on K and TOC is crest> concave>convex. Losses of TP, TN, NH4+-N, NO3--N, K and TOC have typical power function increase in the hydrological year.3. According to the monitoring of weeding and no weeding runoff plots and the indoor simulated coverage rainfall test results. The soil erosion of no weeding No.7plot and weeding No.6plot is obvious different. The sediment yield of No.7plot is reduced23.9%than No.6plot. Especially during the typhoon season, the best effect in sediment reduction is September, the reduction is62.2%. In the artificial simulation of covering rainfall, the soil and water conservation benefit relation is, the upper and lower cover slope> lower cover slope> upper cover slope> bare slope.4. Compare the nutrient loss of different management measures test area runoff plots. It shows that runoff plot keep of grass covered get a better effect in maintaining soil nutrients than the weeding runoff plot. TN, NH+-N, NO3--N, TP,K and TOC content of runoff losses in the No.7plot decrease respectively by9.0%,34.7%,25.5%,8.6%,19.2%and18.9%than No.6plot.5. Combining test results and southern red soil hilly region inherent characteristics of soil erosion and nutrient loss. Draw the conclusions that to keep the soil and nutrient:Firstly, to improve the situation steep hill farming areas, such as use cross slope planting, and artificially reducing the operating terrain slope sloping farmland. Secondly, due to the temporal and spatial distribution characteristics of soil erosion and nutrient loss, soil and water conservation measures should be laid before the rainy season. Mainly include lay hedgerows and grit chamber for the convex and concave slope. Tillage, fertilizer and pesticide spraying and other farming practices should be avoided before the rainy season. Lastly, based on the actual situation of sloping hills of southern, no-till, minimum tillage measures need to be used during farming. Using stubble on the ground and keep a certain amount of grass coverage will play better soil and nutrient retention effect. |
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