Improved Nutrient Management on Mineral and Organic Soils of South Florida through Soil Electrical Conductivity Mapping.

Nutrient management can be improved by identify spatial variability within a field followed by the employment of site-specific crop management. Apparent soil electrical conductivity (EC_a), measured with electromagnetic Induction technique using on-the-go sensors, can be used for rapid and non-destructive determination of spatial variability. However, the relationships between spatial variability of EC_a and soil nutrients in not clear for the organic and mineral soils of south Florida. This study was conducted to develop correlations between soil EC_a and various soil properties in the Everglades Agricultural Area (EAA) of south Florida, and to compare grid and zonal soil sampling techniques. Data on soil EC_a was collected using EM-38 meter (Geonics Limited) in horizontal and vertical dipole modes. Two fields were sampled for each of mineral and organic soils and were divided into 1-acre grids to collect data on soil EC_a, pH, P, K, Ca, Mg, and Si from the middle of each grid. For mineral soils, organic matter was also determined for each soil sample. The EM-38 meter was also towed behind a vehicle to collect continuous soil EC_a data to develop soil EC map and delineate various EC zones within each field. Significant correlations were observed between soil EC_a and pH, P, and Mg in organic soil; and EC_a and P in mineral soil. However, no correlation was observed between soil EC_a and K. We also observed that soil sampling based on EC zones (Zonal sampling) using EM-38 measurements was not an improvement over the traditional one-acre grid soil sampling technique. Results indicated that soil EC_a can be used for limited improvement in nutrient management for the mineral and organic soils of the EAA.