Research On Soil Quality Evaluation In The Loess Plateau Under Different Land Use Type

Soil quality has direct influence on the sustainability of agricultural production. Soil and water loss and the contradiction between people and land is a very prominent problem in the Loess Plateau. So the study of soil quality has important significance. On the basis of some research findings in recent years, this research focuses on the evaluation index problem of the Loess Plateau. By means of sampling analysis and investigation of typical small watershed, this paper analyzes the soil quality evaluation index. By using correlation analysis, sensitivity analysis, principal component analysis and discriminant analysis, the evaluation index was determined. Then, soil quality comprehensive evaluation model was established. For regional soil quality assessment and improvement of the loess plateau region provides reference and basis for soil quality. The main results were as follow:1. Soil mechanical composition of coarse powder percentage is the highest(60%) in this area. The soil particle composition differences are not obvious. The texture of soil is single in the area. Aggregate content of overall performance in surface soil aggregate content is higher than that of deep soil. Soil aggregate content in the form of natural forest plantations of grassland is higher than the grass and agricultural land, garden land and wasteland in different land-use types. The highest soil reunion degrees in natural forest land. The reunion of soil degree is the lowest in the garden and wasteland. Woodland and grassland soil characteristics micelle are higher than agricultural land, garden land and wasteland. Soil bulk density is relatively stable. The soil total porosity difference was not significant.2. The soil organic matter content of the highest in the surface soil. Soil organic matter content in soil increased with the increase of the depth of the reduced gradually. Soil organic matter content in natural arbor forest and shrub is the highest. Soil organic matter content in wasteland farmland and orchard is the minimal. The soil nitrogen presents with similar distribution characteristics of soil organic matter. Total phosphorus content in different land use types and soil layer depth showed little difference. Soil available P in soil on the surface was significantly higher than deep soil. Soil available P content change present a natural arbor forest, farmland and garden plot available phosphorus content was significantly higher than that of other land use ways. Soil total potassium and available potassium content were the highest in 0-20 cm soil layer. Soil total potassium content in soil profile at all levels between the overall differences. Coefficient of variation of soil available potassium in the whole study area is larger. Available k content in soil on the surface and deep soil exist significant differences. The soil p H value increased slightly down the soil profile. The variation coefficient of soil cation exchange capacity is 8.34%-44.77%. The variation coefficient of soil electrical conductivity is smaller. Soil electrical conductivity is gradually increased down the soil profile.3. All kinds of enzyme activity are the tallest in surface soil. All kinds of soil enzyme activity of urease, inverted and alkaline phosphatase in the study area remit the uneven distribution. The distribution of soil urease and organic matter and available nitrogen distribution are very similar. Natural arbor forest and shrub land soil inverted activity were higher than in farmland. The distribution of soil alkaline phosphatase and available p distribution are very similar. Variation coefficient of protease and catalase in soil differences compared with the former three enzymes is smaller.4. Through the study of correlation between indicators of soil quality shows that: Soil physical clay standard and in addition to the density of other soil physical quality indexes have significant correlation. Bulk density and CMR has significant negative correlation. Organic matter and in addition to the conductivity of other soil chemical quality indexes have significant correlation. Soil p H indicators and other indicators are showing a significant negative correlation. Soil total nitrogen and available nitrogen indicators and other indicators were significantly related to related and tube. Soil total potassium and available potassium and other indicators are relatively significant correlation and correlation. Soil invertase index and the correlation between conversions of nitrogen on urease significantly higher than that of related to the transformation of phosphorus of the correlation between alkaline phosphatase. Soil index of alkaline phosphatase and protease and invertase present a very significant positive correlation between. Soil protease index and alkaline phosphatase is extremely significant positive correlation relationship between indicators. Soil index of protease and catalase, urease and invertase were negative correlation.5. Using sensitivity analysis, principal component analysis, correlation analysis, discriminant analysis and other mathematical analysis methods to analyze 25 items of soil quality indicators in the Loess Plateau. 7 soil quality evaluation indicators has been chosen: organic matter, total nitrogen, available phosphorus, clay, aggregation rate, invertase and alkaline phosphatase. The loess plateau soil quality comprehensive evaluation system is established. This evaluation indicator system has the high representative. This evaluation indicator system is suitable for the loess plateau soil quality evaluation. Evaluation equation established by stepwise regression analysis.6. By making the study area soil quality classification standard, determine the regional soil quality grade. In the study, soil quality differences between different land-use types. The soil quality of natural arbor forest is the highest. The study area of soil quality overall level is in the medium to low level. Soil quality is decreased with the increasing of soil depth in different land-use types. Soil on the surface of the soil quality index was significantly higher than that of deep soil. The loess plateau region returning farmland to forest and grass measures have significant effects on soil quality. Artificial shrub forest and grass for soil quality index is mainly concentrated in the soil. In the short term has a significant role to the improvement of the soil quality. Artificial arbor forest impact on soil quality index is mainly manifested in the longer term. Artificial arbor forest land on the surface and deep soil quality all has the positive effects of sustained and stable.