Mapping and Assessment of Within-Field Spatial Variability of Soil pH, Electrical Conductivity, and Particle Size Distribution to Delineate Management Zones

The study aimed to evaluate the spatial distribution of soil pH, electrical conductivity (EC), and particle size distribution within a seven-hectare field in Los Baños Laguna, Philippines using the ordinary kriging method and to utilize the interpolated maps to delineate management zones. Fifty soil samples were collected from the surface layer at a depth of 0–20 cm using a random sampling technique. On the basis of the obtained results, it was found that the area has an acidic pH, medium-textured soil with low soluble salt content. Geostatistical analysis revealed that soil EC and clay content exhibited strong spatial dependence, while soil pH and silt were observed to have a moderate spatial dependence. In contrast, sand exhibited weak spatial dependence. The spherical model was identified as the optimal fit for soil pH, clay content, silt content, and sand content, while the exponential model was deemed most suitable for EC. Three distinct management zones (MZs) were delineated based on the spatial variability of the selected properties. MZ1, the largest zone covering 82.10% of the area, is characterized by a weakly acidic, clay loam soil while MZ2, comprising 15.11% of the area, has a weakly acidic loam soil. MZ3, the smallest zone occupying 2.79% of the area, has a highly acidic loam soil and may require frequent as well as intensive lime applications. These findings highlight the varied spatial dependency and distribution of soil characteristics even in a relatively small area and the usefulness of the interpolated maps as a valuable tool to identify specific management zones.