Study On Spatial Variability Of Soil Physical Properties And Water Infiltration Capability

The spatial variability of soil physical properties in cultivated area is of great significance for evaluating the soil porosity situation, suitable cultivation condition and the restoration of farmland productivity, at the same time providing reference for the rational distribution of modern agriculture. Study on spatial variability of soil properties quantitative is helpful to the scale and intensive production of agricultural production, which is beneficial to the development of agricultural production. This paper applied traditional statistics and geostatistical method to study cultivated soil characteristics spatial variability, and also in different depths of profiles(0-10 cm, 10-20 cm, 20-30cm). Used Phillip model and Kostiakov model fitted infiltration(capillary rise) measured data, the best model to gain the infiltration(capillary rise) parameters as infiltration rates(A) and stable infiltration rates(ic); Shape preserving, spline interpolation and quadratic polynomial regression were used simulating and predicting infiltration rates(capillary water infiltration rates) to verify the stable infiltration rates(ic) precision. Furthermore, researched on spatial variability of A and ic. Analyzed the correlationship infiltration parameters(cumulative infiltration volume(1h), infiltration rate(1h), ic) to soil properties. Research results showed that:(1) Silt content, sand grain content and pH was weak variation, including soil water content, soil bulk density, clay content and electrical conductivity which belong to the medium variation. Soil water content and soil bulk density exhibited strong spatial correlation, p H and EC was spatial correlated moderately. Clay content, silt content and sand content fully independence.(2) Different depths with soil water content spatial variability followed by moderate-weak-moderate, soil bulk density, silt, sand and pH at all levels were weak variability, clay and EC at various levels were moderate variability. 0-10 cm depth of Nugget/Sill showed that the soil bulk density, EC, pH, clay had a strong spatial correlation, sand and silt medium spatial correlation, soil water content were completely independence; 10-20 cm depth of Nugget/Sill showed that the soil bulk density, clay, pH were strong spatial variability, soil water content, silt, sand and EC, were not correlation; 20-30 cm depth of Nugget/Sill showed that the soil water content and clay particles showed a strong correlation, others opposite.(3) Krigged surfaces of soil properties identified that soil water content spatial distribution was obvious, which was contributed by the topography, slope and pattern. Spatial distribution of soil bulk density had a little difference, some areas had a higher value of soil bulk density may be caused by the large-scale compaction. The spatial distribution of clay content、silt content and sand grain content was relatively complicated. Spatial distribution variation of pH was not enough obvious.The distribution of electrical conductivity was in the shape of patch and band. The difference of electrical conductivity was significant in the northeast of study area and the value of it was great.(4) Krigged surfaces of soil properties in different depths identified that the west of study area 20-30 cm depth soil water content was higher and two lower values in the east. 0-10 cm depth soil bulk density was in little change. Distribution of 10-20 cm depth soil bulk density was in the shape of band and patch and presented obvious high in the central position. The distribution of clay content was in the shape of band and patch in different depths and the high value area of clay content appeared in the sample line cross location. There were two higher and two lower of 0-10 cm depth pH. The spatial distribution of 10-20 cm depth pH was obvious, there were two highest areas, four higher and three lower. On the whole, the 10-20 cm depth pH was higher than 0-10 cm depth. 0-10 cm depth electrical conductivity value was higher in the northeast and most in northern and eastern area was lower.(5) Based on Matlab fitted sample line different depths soil infiltration measured data(capillary water rise measured data), Phillip model was the best model. Used shape preserving,spline interpolation, quadratic polynomial regression fitted different depths infiltration rate of capillary water and infiltration rate, the result showed that the Shape preserving was best, and it prediction infiltration rate after infiltration experiments consistent with stable infiltration rate. This identified stable infiltration rate had a higher precision, can be fitted sorptivety rate in Phillip model.Every depth soil capillary water upward parameters spatial variability analysis shows: every depth ic and A were moderate variability. A were not have spatial correlation on 0-10 cm and 10-20 cm depth, 20-30 cm depth A was adverse, had a strong spatial correlation, ic was moderate variability and other depths has a strong spatial correlation.(6) Soil infiltration parameters spatial variability analysis shows: A was the moderate variability on each depth, ic were weak variation on 0-10 cm depth and 10-20 cm depth, and ic was moderate variability on 20-30 cm depth. A had a strong spatial correlation on 0-10 cm and 10-20 cm depth, A was fully independent on 20-30 cm depth. ic were not have spatial correlation on 0-10 cm and 10-20 cm depth, but the 20-30 cm depth ic with a strong spatial correlation.(7) Correlation infiltration capability parameters to soil properties every depth analysis showed that 0-10 cm depth cumulative infiltration volume(1h) was related to the soil clay content, the more cumulative infiltration volume, the less soil clay content. 10-20 cm depth infiltration rate was related to the EC. The more EC, the infiltration rate was gradually reduces. It also showed that the soil salt content influenced the infiltration capability. 20-30 cm depth infiltration rate(1h) was related to soil silt content. If the soil silt content was redundancy, the infiltration rate was lower.(8) Correlation characteristic of capillary water upward to soil physical/chemical properties every depth analysis showed that the 0-10 cm depth cumulative infiltration volume of capillary water(1h) and EC had a positive correlation relationship. The 10-20 cm depth cumulative infiltration volume of capillary water(1h) was a positive correlation relationship with EC and soil silt content; Stable infiltration rate and EC、 soil silt content had a positive correlation relationship; Cumulative infiltration volume of capillary water(1h) and stable infiltration rate with soil silt content have a negative correlation relationship. 20-30 cm depth infiltration rate of capillary water(1h) and cumulative infiltration volume of capillary water(1h)、EC and soil silt content also had a positive correlation relationship.