SPATIAL DEPENDENCE AND RELATIONSHIPS OF ELECTRICAL CONDUCTIVITY TO SOIL ORGANIC MATTER, PHOSPHORUS, AND POTASSIUM

摘要

Apparent electrical conductivity (EC_a) can be an indirect indicator of soil nutrient concentrations, and strong relationships between EC_a and nutrients may help delineate fertility management zones. The objectives of this study were to determine therelationships among EC_a, organic matter (OM), P, and K and to assess the spatial dependency and correlation components of such relationships. Spatial correlations and relationships of EC_a with OM, P, and K were determined using geostatistical and regression analyses. EC_a was measured in parallel transects 4.6 m apart in adjacent Indiana (United States) fields with multiple soil series in 2001, 2002, and 2003. Electrical conductivity, OM, P and K were strongly spatially dependent. Spatial correlations between EC_a and these variables were cyclic: positive at distances of &40 m, but negative at distances &70 m. Organic matter, P, and K showed relatively low but significant correlations with EC_a in all the 3 years of study. Maximum correlations wereobtained with OM, P, and K (r=0.55, 0.50, 0.53, respectively) when soil moisture content was relatively higher in 2003. Data separation by soil series improved correlations between EC_a and soil chemical attributes when the soil was a Mollisol, but not for an Alfisol. Regression models showed that EC_a was significantly related to the variables but that EC_a failed to detect concentration changes and explained &7% of the variability of these nutrients. The results suggested that EC_a has limited usefulness in estimating soil chemical properties or in defining possible management zones for OM, P, and K in these soils.