The Research Of Comprehensive Measure And Variability Of Soil Field Capacity In Horqin Dune-meadow Regions

This paper takes the sand dune-meadows of horqin in the Inner Mongolia as the study area,231 field emplacement and sampling soil sampling points, determined by Wilcox and layout 49 water sampling points, with a surrounding box-flood irrigation method, determination of 0～40cm the soil field capacity. Take the 20cm soil moisture characteristic curve method was used to get the point of the field capacity. Study on the selection of the representative in the ecopoints 6 soils, analysis of soil moisture after rainfall in 0-40cm of soil in the process of change. Comparative analysis of various methods of field capacity data, the following conclusions:1. The study area is divided into eight kinds of landforms. And analysis the physical and chemical parameters of the soil under different landforms. Field water holding capacity and the saturation water content have had an excellent relationship.2. During the study, four kinds of methods for determination of field capacity variation largely consistent indifferent physiognomy type areas, but the number varies greatly. Pressure Board method can get same test results with Wilcox method at suitable of negative pressure. But the test results of Wilcox method is big different with the test results of irrigation method and natural precipitation method. While, surrounding box flooded irrigation method is also effected by early rainfall and making measurement value partial big. When using surrounding box flooded irrigation method measure field holding water should avoid early rainfall or increase test time。3. When the rainfall at 60mm, natural precipitation method can get more accurate values of the field water holding capacity of the 0-40cm soil at the dune areas with big buried depth of groundwater. recommended sampling time at sand dunes area is 12～24 h, meadow area with small buried depth of groundwater is influenced by groundwater. unable to obtain accurate field capacity value. Wilcox method is not influenced by groundwater. associated with dehydration time, selecting suitable dehydration time can get the correct value of field capacity, sand select 36～40h, sandy loam and loamy sand using 44-48h.4. Geostatistical analysis is used to study the spatial distribution of soil field capacity with the test results of Wilcox method. Results:field water capacity showed a strong correlation. after cross validation, selecting the best model of variogram and using the universal kriging method to simulate the spatial distribution of soil properties. Whole shows around the lake as the center gradually decreasing trend, correlation between dry density and the best, there was a negative correlation.