Site-Specific Compaction, Soil Physical Property, and Crop Yield Relationships for Claypan Soils

Soil compaction is a concern in crop production and environmental protection. Compaction is most often quantified in the field, albeit indirectly, using cone penetrometer measurements of soil strength. The objective of this research was to relate soil compaction to soil physical properties and crop yields. Penetrometer cone index (CI) data and prismatic soil strength index (PSSI) from an on-the-go sensor were obtained from two claypan soil fields with spatial variations in soil texture, bulk density, and water content. Auxiliary data included bulk density, water content, and apparent soil electrical conductivity (ECa) as a surrogate for soil texture. CI, PSSI, and derived variables were significantly but weakly correlated to water content and ECa at all sites. Examination showed that different CI profile shapes were characteristic of different ECa levels. Regression analysis represented > 40% of the variation in CI at the 15- to 25-cm soil depth as a function of ECa and soil water content, and the boundary line method was suggested for additional analysis. Compaction variables were only weakly related to grain yield, with negative correlations in good growing seasons and positive correlations in water-limited seasons. More in-depth analysis would be required to better define the yield-CI relationship in these data. However, the ECa-CI (or PSSI) relationship may be useful to locate areas most likely to exhibit high levels of compaction, thus making the process of characterizing within-field compaction variations more efficient.