Effect And Mechanism Of Hedgerow On Phosphorus Loss From Lime Soil In Sloping Field

Xiangxi River is the largest tributary of the Three Gorges reservoir in Hubei Province,since the Three Gorges reservoir impoundment,the blooming phenomenon is occurrence frequently,the ecological environment of the reservoir area and the quality of people's lives constitute a serious threat.Due to the large slope of the cultivated land and concentrated in the low elevation area of the upper part of the river,the reservoir area farmers to increase the yield of the crops,rely heavily on the chemical fertilizers,because there is no any control measures,the farmland soil and nitrogen nutrients erosion directly into the Xiangxi River,greatly improving the risk of water environment in the reservoir area.Therefore,based on summarizing the measures of soil and water loss prevention and control and controlling the output of agricultural non-point source pollution,this paper chooses the lime-sloping farmland with high-risk pollutant output characteristics in Xiangxi River basin of Three Gorges Reservoir area as the research object.Under the condition of not destroying the original slope farmland ecosystem,the construction of runoff area,establishment of hedgerows system and stone canal,based on the methods of field artificial rainfall and experimental analysis.Study on the effects of hedgerow system on soil and water conservation and phosphorus loss of sloping farmland under different rain intensity,plant mix and slope conditions.The effects of hedgerow system on physical and chemical properties and phosphorus forms of surface soil in sloping farmland were studied.The main conclusions are as follows:?1?The rainfall intensity and slope significantly affected the characteristics of runoff sediment yield in sloping land,the runoff and sediment yield increased significantly with the increase of rain intensity and slope.The hedgerow and stone system could effectively prolong the initial runoff time,significantly reduce the slump land runoff and sediment yield.Through the simulated rainfall test,compared with the bare land,the stone system,Gardenia hedgerow and ryegrass hedgerows intercept rate of runoff was between 24.1%and 57.4%in the runoff period of 60min,the intercept rate was between 30.6%and 82.2%,and the efficiency of interception was ryegrass hedgerows>gardenia hedgerows>stone system.?2?The loss of phosphorus on the sloping land was dominated by sediment in different rainfall intensity and slope,and the loss of phosphorus in the sediment accounted for 75.9%to 82.6%of the total phosphorus loss in the lime soil farmland,rain intensity and slope had little effect on runoff and sediment concentration.The hedgerows system has the effect of reducing the concentration of phosphorus in the runoff.The hedgerows system reduces the runoff and sediment output of the sloping land,so as to achieve the purpose of less phosphorus loss,the intercept rates of total phosphorus loss in runoff and sediment were 32.5%-57.8%and 43.6%-72.2%.Under different measures,the cumulative loss of phosphorus in the sand and the runoff time have good linear fitting relationship.?3?The hedgerows system has the effect of improving the soil physical and chemical properties of the surface farmland soil.After a rainy season?April-September?,the soil bulk density decreased 5.4%-18.8%,water content increased by2%-8.3%of the hedgerows compared with the control group,the contents of organic matter,total nitrogen,available nitrogen,total phosphorus and available phosphorus were slightly increased,and the nutrient enrichment was sorted as gardenia hedgerows>ryegrass plant fence>stone system.The effect of soil feldspar on the surface soil was changed by the hedgerows system,the fine soil content was increased,the sand content was decreased.The soil fine particles were obviously enriched in the hedgerows.?4?The phosphorus in the lime soil mainly with the inorganic phosphorus form,accounting for 80%of the total phosphorus,Ca₂-P and Ca₈-P accounted for 16%-19%of the inorganic phosphorus,compared with the control group,the effects of two hedgerow treatments on the accumulation of Fe-P,O-P and Ca₁₀-P were significant in the soil.The concentration of Ca₂-P and Ca₈-P in the plant fence was significantly lower than that in the control land and stone system.The correlation of the hedgerows system showed that there was a significant correlation between soil bulk density and clay content with different forms of phosphorus in sloping soils.