Authors : Yong Jiang , Yuge Zhang and Wenju Liang
Abstract: Geostatistics was applied to assess the spatial distribution of exchangeable calcium (Ca), magnesium (Mg), potassium (K), sodium (Na) and the sum of exchangeable bases (SEB) in the cultivated horizon in a Chinese Ecosystem Research Network (CERN) site in northeast China. A 42�30 m plot was divided into grids with 7�5 m spacing that included 49 sampling points. Soil samples were collected from depths of 0-10 cm and 10-20 cm. The results showed that most of the variables analyzed had normal distributions in the both horizon. Each of the variables presented a spatial structure and they were modeled quite well. Calcium, Na and SEB that showed smaller values of nugget effects in the both horizons indicated that the agricultural land use practice somehow favored close distance continuity for these variables. The spatial dependence range was 11.80-91.00 m, indicating that the grid spacing was adequate for the characterization of the spatial variability of the exchangeable cations. Both the variograms and the maps obtained with kriging showed that the spatial variability for the exchangeable cations and SEB was tended to be greater in the subsoil than in the topsoil, suggesting that the land use practices had led to more homogeneity in the top soil than in the subsoil. The maps obtained with kriging also showed that the spatial variability was stronger in the north part of the plot near a traffic passage than in the remainder area, indicating the effect of anthropogenic disturbance on soil exchangeable cations.
Yong Jiang , Yuge Zhang and Wenju Liang , 2008. Field-Scale Variability of Soil Exchangeable Cations in a Chinese Ecological Research Network (CERN) Site. Agricultural Journal, 3: 208-215.