| Hedgerow is an agroforestry technology of water conservation measure which is used for intercepting runoff and sediment,reducing slope farmland non-point source pollution,improving soil fertility.To explore the effect of hedgerow on physicochemical properties and soil anti-erodibility of surface soil in slope farmland,after 3-5years of plantations of the Vetiveria zizanioides and Leucaena leucocephala,runoff plots were compared and analyzed combined with sediment sample and laboratory analysis in Suining soil and water conservation experimental station.The results showed as followed.(1)The soil sand content in hedgerow plot was 49-92%of that in control group.The soil sand content was negatively correlated with fractal dimension of soil particle composition.While the silt and clay of soil were positively correlated with fractal dimension of soil particle composition whose correlation is remarkable.In Vetiveria zizanioides hedgerow plot of 10° slope,the fractal dimension of soil particle composition was maximum.The R0.25 in hedgerow farmland is 110-119%of that of control plot.This law in 10° plots were more significant than that of in 15° plot.Aggregates fractal dimension of hedgerow plot was less than that of control group.Mean weight diameter(MWD)and geometric mean diameter(GMD)were significantly greater than that of control group.Fractal dimension of soil aggregate minimum,MWD and GMD reached maximum value in Vetiveria zizanioides hedgerow of 10° plot.The total soil porosity in hedgerow slope farmland was 50.2-53.2%,which is higher than that of control plot(45.5-48.5%).While soil capillary porosity in hedgerow plot was lower than that of control plot.Non-capillary porosity of surface soil in hedgerow plot was significantly higher than that of control plot.(2)Soil physicochemical properties of farmland were analyzed in 2014-2015 years.Compared with the control group,after 4-5 years of planted hedgerows,the SOC(organic carbon)and TN(total nitrogen)content of surface soil in hedgerow plot increased significantly.While TP(total phosphorus)and TK(total potassium)content decreased significantly.Loss of soil nutrient was more remarkable for 15° farmland.Hedgerows can significantly increase SOC and TN content of surface soil,while TP and TK content of soil decreased slightly.C/N ratio(SOC:TN)of hedgerow farmland was larger than that of control plot.C/N ratio of the underside hedgerows is larger than that of upperside hedgerows.In same hedgerows,C/N ratio of 10° farmland was larger than that of 15° farmland.Soil water stable aggregates was associated with nutrient content.In the smaller particle size,soil organic carbon and total nitrogen content was significantly positively correlated with<0.25 mm aggregates,wheras a significant negative correlation with 2mm-5mm aggregates.(3)The selected 11 indicators can be represented by 2 principal components to show soil anti-erodibility.Overall,Water stable aggregates and its related indexes can be used as the best indicators for evaluating the soil anti-erodibility.Compared with control plot,hedgerow plot significantly improved the anti-erodibility of surface soil.The soil anti-erodibility index of Vetiveria zizanioides and Leucaena leucocephala hedgerow in 10° farmland were 7.0 times and 2.3 times larger than that of control plot.Vetiveria zizanioides hedgerow plot in 15°farmland was 26.7 times larger than that of control plot.While the soil anti-erodibility showed the differences in both sides of hedgerow.The soil anti-erodibility index underside hedgerow plot of 10° and 15°farmland were 2.0 times and 1.5 times larger than that of upperside.The underside of soil erodibility index of Leucaena leucocephala hedgerow in 10° farmland was 1.07 times larger than that of upperside hedgerow.Overall,hedgerows improved construction of soil and enhanced anti-erodibility of soil.Moreover,hedgerow's effect on the underside was more remarkable than that on the upperside.In 10° farmland,the effects of Vetiveria zizanioides hedgerow on soil physical structure and anti-erodibility were stronger than that of Leucaena leucocephala hedgerow.In the future,we should choose suitable hedgerow species to control soil erosion,especially in upperside of hedgerows. |
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