Spatial Variability of Soil Fertility Quality Indices in Northeast China

Geographical information system(GIS) combined with Geostatistics was applied to reveal the spatial variability of soil fertility quality indices i.e.,soil pH,organic matter,available P,available K and clay in the topsoil (0~20cm) in the northeastern area of China.The results showed that theoretical semivariogram models of soil pH and clay were best described with an exponential model,whereas the organic matter,available P and available K were best fitted with a spherical model.The ratios of nugget to sill of available P and available K were 46.63%,49.91%,respectively,indicating that the spatial correlation of the two fertility indices was moderately dependent.The ratios of nugget to sill of pH,organic matter and clay were 10.80%,16.57% and 12.88%,respectively, indicating that the spatial correlation of the three fertility indices was strongly dependent.The integrated index of soil fertility quality was calculated based on each sample index,then from the spatial distributed map of soil fertility quality we could get the integrated index in the region.