Large area spatial variability of soil chemical properties in central Brazil

Understanding the spatial distribution pattern of soil properties is important to determine soil constraints to plant nutrition and appropriate management of soil resources in recently cultivated areas. This study addresses spatial variability of exchangeable potassium (K-e) and sum of bases (S-B) in Mato Grosso State, Brazil. Geostatistical methods described the spatial variability and predicted along four transects crossing different soil mapping units and land use types. Ordinary kriging appropriately estimates values in unsampled areas. It identifies places where more intensive sampling is required. This study shows that land use affected spatial variability of K-e and S-B in well-defined structural patterns. In particular, K-e exhibits a strong spatial dependence and anisotropy in two horizons. Traditional surveys of soil fertility, together with data from soil survey maps, can be used in combination with geostatistics by decision-makers to support management planning and to predict indicators related to soil quality as a measure of sustainability. As it turns out, K-e and S-B need to be sampled at different densities, and soil survey information can be used to advantage to reduce the sampling efforts of S-B by 96%. (C) 1997 Elsevier Science B.V.