Spatial variability of fractal dimension for soil particle size distribution and particle volume percentage in farmlands

The spatial variability of soil physico-chemical properties for saline soil was during drip irrigation under plastic mulch and it influenced irrigation management. In this paper, based on soil sampling and the measured results of soil particle size distributions (PSD) at three scales, the quantitative relationships between soil PSD fractal dimension and particle volume percentage were discussed. Their classic statistical and geo-statistical characteristics were analyzed at each scale and all scales. Fractal dimensions of particle volume percentages at different scales were determined according to the semi-variogram models of soil PSD, and the contour maps were drawn. The results showed that: there were positive correlations between soil PSD fractal dimensions and clay volume percentages. Because specific surface area of small particles was larger than that of big particles, the soil PSD fractal dimension increased when the clay volume percentage increased. There was no strong variability for both soil PSD fractal dimensions and particle volume percentages at each scale. In the semi-variogram models of soil PSD fractal dimensions at three scales, both the nuggets and the sills were very low. The concentration degree and trends in contour maps of soil PSD fractal dimensions and clay volume percentage at 50 m scale were similar, but for contour maps of sand volume percentages and silt volume percentages, the concentration degree and variation trends were opposite. This study showed that there were certain scale dependence of soil PSD fractal dimension and particle volume percentages.