Evaluation On Soil Improvement Benefit Of Different Fruit-Grass Intercropping Types In The Three Gorges Reservoir Area

In order to study the effect of compound model of the economic forest on soil improvement benefit and choose one best economic forest model.This study have set different field economic forest plots,and compared with traditional agriculture crop land respectively.During the different plant growth period(April 26,2011(time A)and September 22,2011(time B))collect soil sample of different model plots(1,Citrus reticulate Blanco.and Lolium perenne L.(GH);2,Citrus reticulate Blanco.and Cichorium intybus L.(GJ);3,Citrus reticulate Blanco.(GC);4,Eriobotrya japonica(Thunb.)Lindl.and Lolium perenne L.(PH);5,Eriobotrya japonica(Thunb.)Lindl.and Cichorium intybzus L.(PJ);6,Eriobotrya japonica(Thunb.)Lindl.(PC);7,Dimocarpus longan Lour.and Lolium perenne L.(LH);8,Dimocarpus longan Lour,and Cichorium intybus L.(LJ);9,Dimocarpus longan Lour.(LC);10,farmland(CK))to determine the effects of different models on soil bulk density,porosity,mechanical composition,organic matter,soil nutrient,aggregate structure,infiltration capacity.On the other hand,the physical and chemical characteristics of soil are compared between different models,and by such comparison,we know the effect of different compound model of the economic forest on soil improvement benefit,and choose one best economic forest model.The main results of this study are summarized below.The differences of the soil bulk density between different compound model of the economic forest during A and B period are significant(P<0.05),the results showed that PH>PC>GC>PJ>GJ>GH>LC>CK>LH>LJ and PC>PH>LJ>LC>GC>LH>GJ>PJ>GH>CK respectively on A and B period.The differences of the non-capillary porosity,capillary porosity and the total porosity between different compound model of the economic forest during A and B period are significant(P<0.05),which showed that different compound model have different effect on soil porosity improvement benefit,GH>PJ>GJ>LH>GC>CK>LJ>PH>PC>LC for the non-capillary porosity,LJ>PH>PJ>LH>GJ>LC>PC>GH>CK>GC for capillary porosity,and PJ>LJ>PH>GJ>LH>GH>LC>PC>CK>GC for the total porosity.Due to the mechanical composition between different compound model of the economic forest,which showed that the biggest content of sand,silt and clay for CK,GJ,GH respectively during A period,and for CK,LH,LH respectively during B period.The regression analysis results showed fractal dimension had a positive correlation with clay content,and a negative correlation with sand,silt content,and the correlations are not significant(P<0.05),which showed that fractal dimension could be used to describe the change characteristics of clay content.The results also showed that PJ>GC>GJ>PH>PC>GH>LC>LH>CK>LJ of>0.25mm air dried aggregate content between different compound model of the economic forest during A period,and PJ>PC>PH>GC>LH>LJ>GH>GJ>CK for>0.25mm water stable aggregate content.The biggest MWD value of>0.25mm air dried aggregate for GJ and the smallest for LJ,and the biggest MWD value of>0.25mm water stable aggregate for LC and the smallest for LJ.CK>LJ>LH>LC>GH>GJ>PC>PH>GC>PJ for the fractal dimension value of>0.25mm air dried aggregate,and the biggest fractal dimension value of>0.25mm water stable aggregate for CK and the smallest for PJ.PJ>GJ>GC>PC>PH>GH>LC>CK>LJ>LH for>0.25mm air dried aggregate content,and PJ>LJ>PC>CK>LH>PH>LC>GC>GJ>GH for>0.25mm water stable aggregate content during B period.the biggest MWD value of>0.25mm air dried aggregate for GJ and the smallest for LH,and the biggest MWD value of>0.25mm water stable aggregate for PJ and the smallest for PH.LH>CK>LJ>LC>GH>PH>GC>PC>GJ>PJ for the fractal dimension value of>0.25mm air dried aggregate,and the biggest fractal dimension value of>0.25mm water stable aggregate for GH and the smallest for PJ.The content of 0.25?0.05mm?0.05?0.01mm particles account for a large part of soil micro-aggregate in different compound model of the economic forest during A and B period,the biggest MWD value of micro-aggregate for PC and the smallest for LH during A period,the biggest PCM value for LH and the smallest for PC,and the biggest D value for PJ and the smallest for PC.Also,the biggest MWD and PCM value of micro-aggregate for GC and the smallest for LH during B period,the biggest D value for PJ and the smallest for GH of 2.395.There are significant differences of parameter size between different models.The value of initial infiltration rate,average infiltration ratio,stable infiltration rate,cumulative infiltration amount,standard deviation for LJ,LH,CK are bigger when compared with that for PC,PH.The infiltration process on different period of different models was simulated by using Kostiakov equation?Horton equation?Philip model,the results showed that the coefficient of determination simulated by Horton equation was bigger,which indicated that the Horton equation was more suitable for simulating the infiltration process.During different period,the factors which influencing stable infiltration rate were different.During A period,the stable infiltration rate had a very significant Power function negative correlation with soil bulk density(P<0.01),a very significant exponential function positive correlation with the non-capillary porosity and total porosity(P<0.01),a significant exponential function negative correlation with organic matter(P<0.05),and a very significant Log function negative correlation with>0.25mm air dried aggregate.During B period,the stable infiltration rate had a significant exponential function positive correlation with the non-capillary porosity(P<0.05),and had a significant linear function positive correlation with total porosity and total nitrogen(P<0.05).The stable infiltration rate can be calculated by using the content of>0.25mm air dried aggregate and sand in A period,and stable infiltration rate can be calculated by using the content of total nitrogen in B period.By using the Principles and Methods of Grey System Theory,we had set up a Comprehensive evaluation index system to analyze the effect of different models on soil improvement benefit by using 22 kinds of indexes,such as Soil bulk density and the non-capillary porosity.The Soil physicochemical Properties of different models had different contributions on the soil improvement benefit.The results showed that the LJ,PJ,GJ,GH model had a better soil improvement benefit both in A and B period,which means Longan and witloof,loquat and witloof,citrus and witloof,citrus and Black hair grass model had a better soil improvement benefit,meanwhile,compared with Black hair grass,witloof was more suitable for in a matching way with economic forest in local area.