Study On Evaluation Of Soil Quality And Erosion Characters In Dry Valley Of The Upper Minjiang River

The physical and chemical property of the soil is an important part of the internalcondition of the influence of soil fertility and integrated to reflect soil quality. Land usemanagement is the direct and profound factors that influence the soil properties.Understanding of the influence of land use management to the soil physical and chemicalproperty is the precondition to improve land use, development of sustainable agriculturepremise and is the key to the recovery of the ecologically fragile vegetation and lies. In thisstudy, the method of field investigation, sampling, field water erosion and indoor experimentwere used. The object of this research is the Minjiang River dry valley area of different landuse types and typical small watershed slopes. The soil fertility characteristics of differentland-use patterns and human activities on soil quality have been studied to explore the factorsaffecting the mechanism of the region runoff erosion and sediment and nutrient loss withrunoff. The main findings are listed as follows:1. The Minjiang River dry valley soil generally thin and rich gravel; higher potentialfertility of soil fertility is low effective, including organic matter, total nitrogen and totalpotassium content of high fertility levels in the natural soil organic matter and nitrogencontentcultivated soils, phosphorus inadequate supply of arable land must be increased byfertilization phosphorus content in order to meet the demand for plant growth; mostly neutralto slightly alkaline soil, and has alkalized gradually; physical and chemical properties of soilbetween the different land use patterns（organic matter, total nitrogen, total phosphorus, totalpotassium, available nitrogen, available phosphorus, available potassium, etc.） showed asignificant difference （P <0.01）. Comprehensive index of soil quality performance for theshrub land （64.79%）> arable land （46.82%） of grassland （43.65%）> bare land （40%）> Corner（25.35%） and soil degradation in the performance of an index for the garden （77.76%）> arableland （43.2%）> the wasteland （14.85%）> shrub land （0）> bare land （-26.07%）. Soil qualityindex （IQ） and soil degradation index （ID） quantitative method for soil quality evaluationresults are not totally consistent, indicating that these two indices can not be equivalent toevaluate the quality of the soil in the area of different land use types, In contrast, thecomprehensive index of soil quality because it takes into account the right of choice of indicators weight is considered a more reasonable way to evaluate the situation of the studyarea, soil quality.2. The Minjiang River dry valley soil texture is mainly silt loam, loam and sandy loamtypes. The proportion was74.5%,18.6%and5.3%, respectively. The soil particle fractaldimension of the body is between2.5011².7825, powder loam> loam> sandy loam. Arableland than the native vegetation filling the woodland soil particles volume integral are thefractal dimension, fractal dimension in the same land use reduces the downward trend withaltitude. Fractal dimension of soil particle volume fraction of clay （<0.002mm） and silt （0.002to0.05mm）, volume fraction and soil potassium content was highly significant positivecorrelation with sand （>0.05mm）, volume one hundred content showed a highly significantnegative correlation with soil organic matter, total nitrogen, total phosphorus, available P andK content did not reach significant level. More coarse soil texture points the smaller thefractal dimension and soil texture, the more segments the greater the dimension of soilparticle size distribution of fractal dimension can be used as an important indicator of thecharacterization of soil structure. The fractal dimension changes can be a goodcharacterization of the trend of changes in soil chemistry, physical properties, can also serveas a comprehensive indicator of the diagnosis of soil fertility and evaluation of soil structure.For understanding soil formation process and its evolution mechanism and so have importanttheoretical and practical significance.3. Different land uses so that the erosion tests runoff, runoff sediment concentration isquite different. However, the overall trend is the erosion over time, the runoff of a graduallyincreasing trend. Produce runoff bare land runoff, followed by shrubs and wheat farmland,grassland and maize cultivated land is the minimum. Runoff sediment concentration with theextension of the production flow time, showing the regularity of a decreasing trend. Grasslandand wheat farmland runoff sediment concentration is less and less time to stabilize, while thebare ground sediment throughout the erosion process and sediment concentration tends to astable time lag in several other land uses. Soil erosion resistance of extended wavy changewith the erosion of time, but all in all continues to meet scour the longer the soil impactresistance, the stronger the law. Native grassland, the greatest impact, followed by wheatfarmland, native bush forest, corn cropland, bare soil erosion resistance minimum. The size ofthe soil erosion resistance and soil silt content have very significant negative correlation,correlation coefficient-0.992; It was a significant positive correlation with sand content, thecorrelation coefficient of0.925; It was negatively correlated with clay content, the correlationcoefficient is-0.796; and soil organic matter content was not significant.4. Rainfall runoff is the Minjiang River dry valley area sediment production on the most important dynamic factor. The upper reaches of Minjiang River is rich in water resources inChina region, is also an important base for the Sichuan Development Features arid valleyagriculture, hydropower project construction on steep slopes in the reclamation process,serious disturbance original soil structure level, the ground vegetation is destroyed resulting inserious soil erosion in the new, artificially accelerate the process of soil erosion in the area.This study runoff erosion and sediment yield as a breakthrough, artificial Scouring field sitetest methods, development and construction in the area of human disturbance groundSEDIMENT simulation study results show that: the slope of5°,10°and15°conditions, theflow rate of2L·min^-1,3L·min^-1,4L·min^-1and5L·min^-1when runoff and drainage flow linearrelationship, the relationship is W=31.999Q-46.497, r=0.9466, sediment yield and watertraffic was a logarithmic function, its relation to Ms=1137.657Ln（Q）+524.252, r=0.9535;slope of the most important factors that affect the the native surface runoff sediment yield,runoff, sediment yield and the slope was linearly correlated, with slope increases runoff andsediment yield linear; sediment yield and runoff are all very close, was a linear correlationbetween changes with increasing runoff and sediment yield also increased its relationsformula Ms=0.028W+0.343, r=0.9589. Theory of human disturbance ground SEDIMENTsimulation study effectively prevents regional soil erosion data has important scientific valueand practical significance for the area of agricultural development and ecologicalconstruction.5. Runoff is the loss of soil sediment and soil nutrient elements of power and carrier.Therunoff in the slope transfer process is actually a process of interaction of runoff with surfacesoil particles in this process, runoff first selective carrying soil fine particles. Compared withthe in situ soil, sediment fine particles, especially clay content increased significantly, leadingto the enrichment of clay sediment. Soil organic matter and total multi-combination with finesoil particles, silt clay enrichment will lead to the enrichment of sediment organic matter andnitrogen in runoff from washing process. Sediment nutrient enrichment by the modulus ofrunoff velocity and erosion, runoff velocity and erosion modulus smaller sediment organicmatter and nitrogen enrichment of higher degree. Slope, directly or indirectly affect the flowrate of runoff and erosion modulus, and thus a significant impact on sediment nutrientenrichment. Divided into two types of insoluble and soluble soil K in runoff erosion process,part of the potassium is dissolved in the runoff solution, Part of adsorption remains in thesediment of potassium in the sediment compared with in situ soil available. The potassiumcontent is low, but under different slope and water flow conditions and organic matter, totalnitrogen enrichment patterns. The same slope, the water flow （washed intensity） increases,some reduction in the accumulation rate of sediment available K, constant water flow, with the increase of the slope, sediment potassium enrichment rate tends to decrease.