Effects Of Land Use On Soil Quality In North-west Of Shanxi Province

The hilly Loess Plateau in north-east of Shanxi Province is one of themost serious region of soil erosion in China. The irrational land-use is themain reason of soil erosion and nutrient loss. Since for guarding againstwind, conserving water and soil, fixing sand and developing animalhusbandry, during the 20th century 60's, a large area of Caraganamicrophylla was planted in the hilly Loess Plateau in north-east of ShanxiProvince. Some regions had also planted the mixed plantation of Caraganamicrophylla and poplar. In this paper, Wuzhai County was taken as theresearch base which locates in north-east of Shanxi Province and is atypical area of the hilly Loess Plateau. In this research base, five land-usestypes, Caragana microphylla, farmland, poplar, fallow land and the mixedplantation of Caragana microphylla and poplar, were chose to studywhether and how the adjustment of land-uses influences soil quality. Theresult can supply foundation for the ecology recovery of the hilly LoessPlateau in north-east of Shanxi Province.This article uses the method which in the open country samplinginvestigation and the room analyzes unifies. First of all, soil propertiesunder five land-uses, Caragana microphylla, farmland, poplar, fallow landand the mixed plantation of Caragana microphylla and poplar in a typicalLoess Plateau region, north-east of Shanxi Province were studied separately.Then, on the foundation of analyzing the soil properties, an evaluatedindicator system including physical indicator, chemical indicator andbiological indicator was developed according to the principle of evaluatedindicator selection. After that, the method of multivariate analysis was usedto carry through rather complete and scientific evaluation: according tosubject function solved how to decide the degree of function, realized thetransaction of original data to the same dimension; as well as utilizing mainingredient analyzing solved how to determine the distribution ofweightiness about every evaluated indicator. Results showed that: (1)Different land uses had different effects on soil properties. Caraganamicrophylla and the mixed plantation could improve soil physicalcharacter, enzyme activity, total nitrogen and organic matter content insoil. Cropland soil was degraded, since cultivation practice improvedbulk density, decreased enzyme activity, soil total nitrogen and organicmatter content in soil.(2)The values of soil quality index of Caragana microphylla, farmland,poplar, fallow land and the mixed plantation of Caragana microphyllaand poplar were 1.410, 1.199, 1.284, 1.046, and 1.459, respectively. Thevalue of mixed plantation of Caragana microphylla and poplar was thehighest of all and that of the Caragana microphylla was the second.Compared with the artificial poplar, Caragana microphylla, the mixedplantation of Caragana microphylla and poplar had higher soil fertility.It was further shown that growing Caragana microphylla and the mixedplantation of Caragana microphylla and poplar were the mostsustainable ways of developing the Loess Plateau.(3)Compared with Caragana microphylla and the mixed plantation ofCaragana microphylla and poplar, the value of soil quality index offarm land descended greatly, and the soil degraded. Cultivation practicesimproved bulk density, decreased enzyme activity, soil total nitrogenand organic matter content in soil. Though a lot of fertilizer includingsome available nutrients, just like Olsen P, was applied to the cropland,the soil quality could not be improved geatly. Appliment of fertilizercould only improve the content of available nutrients.(4)The value of soil quality index of fallow land was the lowest.Comparing with farmland, land fallow could improve total nitrogen,total K, and organic matter content in soil. But the comprehensive soilquality of fallow land was lower than that of farmland. Analyzing andcomparing every soil properties, we can see that the fallow land hadhigher bulk density and lower total porosity than that of farmland. Thiswas related to the artificial practice, such as trampled by human and animal. So the artificial practice was the possible reason which leaded tothe lower comprehensive soil quality of fallow land. But, consideringthe soil nutrients content, land fallow improved soil fertility to someextent.