Assessment of spatial variability of penetration resistance and hardpan characteristics in a cassava field

Abstract

Soil compaction is generally defined as an increase of the natural density of soil at a particular depth. This compacted soil layer spatially varies over the field. Describing within-field variability is a fundamental first step towards determining the size of management zones. The purpose of the study was to explain the spatial variability of penetration resistance (PR) and hardpan characteristics. Soil PR, dry bulk density (BD), and water content (WC) were measured on the nodes of a mesh. Statistical and geostatistical analysis were used to analyse the spatial variability of PR at 5 depths: 0.0–0.1, 0.1–0.2, 0.2–0.3, 0.3–0.4, and 0.4–0.5 m, and hardpan characteristics. PR had the maximum variability among the measured properties. Hardpan lower edge depth varied from 0.297 to 0.714 m, having a mean and CV of 0.411 m and 20.43, respectively. PR was inversely related to WC. Correlation between BD and WC and PR for the same layer was relatively high. PR and hardpan characteristics showed spatial variability across the field, except PR at depth 0.1–0.2 m. Spherical isotropic models fitted all the measured properties. The range of values of the spatial structure was greater than 7.6 m. The results showed that hardpan and PR spatially varied across the field. These results are important in determining the necessary tillage technique as well as the tillage depth and the target compacted area for a suitable land management. These results also have important implications for how site-specific management information should be collected and explained.