Submeter Spatial Variability of Selected Soil and Bermudagrass Production Variables

The optimal resolution at which soil and plant variables should be sensed and treated is not well defined. This study was conducted to determine the semivariance range where soil test and plant variables were related, and to estimate the minimum spatial scale at which variable rate applications of nutrients should be made. Soil and plant analyses were performed in 490 0.3‐ by 0.3‐m plots from bermudagrass ( Cynodon dactylon L.) sod at two locations. Eight soil cores (0–15 cm deep) were collected and composited from each 0.3‐ by 0.3‐m plot. Semivariance analysis was used to estimate the range over which samples of the five soil variables (total N, extractable P, and K, organic C, and pH) and two plant variables (forage total N and biomass) were related. Semivariance statistics including the nugget, sill, correlation range, and integral scale were calculated. Correlation ranges were between 1.9 and 11.4 m with corresponding integral scales between 0.5 and 2.1 m. At one location, P exhibited nested sills with multiple ranges. Results indicate that the fundamental field‐element dimensions (the area over which variable rate fertilizer applicators should sense and apply materials) is likely to be 1.0 by 1.0 m or smaller. To describe the variability encountered in these experiments, soil and plant measurements should be made at the meter or submeter level.