Study On The Soil Quality's Space-time Variation In The Land Rectification Areas

As one of the most important resources, the sustainable use of land is fundamental for the sustainable development of society. Land consolidation is to increase more benefits without increase the area of land use, which is the result of social development. However, more attentions are paid to the quantity increased from land consolidation than to soil quality. This article discussed soil quality changes after land consolidation at different temporal intervals, via specific land consolidation project in highland and plain areas in Tai'an City, and performed soil quality evaluation to provide guidelines for restructured soil sustainable development.The main conclusions are as follows:(1) Classical statistics was adopted to analyze several indicators, like organic matter, available K, available P, alkali-hydrolyzadle N, pH value, conductivity and soil density in land consolidation and reclamation project in highland and plain areas. Bigger variation coefficient indicates more uneven of each indicator. There are big variation coefficients in land consolidation area 1a and 4a, which mean land consolidation and cultivation have obvious impact on the dispersion degree of soil quality. After the comparison of values of average and control of soil nutrients, a trend of approach control values can be seen clearly with the time elapses after land consolidation.(2)Here geo-statistics was adopted to interpret spatial variation of soil nutrients, including spherical model, exponential model, gauss model, and hole effect model, etc. part variation of soil nutrients belong to pure nugget effect, means weak variability of soil nutrients. The variation ranges of soil nutrients are all in 5m (the interval of sampling points), and variations occur in the ranges. Many factors affect soil nutrients including deterministic and stochastic ones. Deterministic factors intensify the spatial correlation of soil nutrients, and stochastic ones reduce these correlations.(3)According to the characteristics of each study area, different indicators were selected to establish evaluating system: soil thickness, soil texture, irrigation facilities, available nutrients (available K, available P, alkali-hydrolyzadle N), organic matter, pH value, conductivity and soil density are selected for highland areas; and groundwater table, soil texture, soil structure, available nutrients, organic matter, soil density, pH value and conductivity for plain area; organic matter, available nutrients, soil density, pH value, EC, compactness and soil porosity for reclamation project areas.(4)Correlation coefficient approach and membership function were used to specify weights and memberships of indicators. Correlation coefficient approach can avoid the subjectiveness of Delphi and AHP, to calculate indicator weights objectively. The degrees of membership were determined respectively, guard-down membership function is sound for available nutrients, conductivity and organic matters, and guard-up for soil density. It's not determine weight of pH values using guard-up or guard-down membership functions, so empirical method was used to quantify it's degree of membership.(5) According to the evaluating results, soil quality increases with the time go by, and the soil quality is higher in 4 years after consolidation and 5 years after reclamation respectively.