Estimation of CI-based Soil Compaction Status from Soil Apparent Electrical Conductivity

Abstract. Regionalization of soil properties is very important for successful site-specific field management. Soil compaction is a critical issue to be detected and managed due to its effects on crop growth. Soil compaction has been conventionally quantified as cone index (CI) measured by an ASABE-standard cone penetrometer, but this approach has limited capability of obtaining the spatially-dense data required for precision agriculture. A significant amount of past research has related CI with apparent soil electrical conductivity (ECa), and recently the potential of ECa to estimate subsoil compaction status through the stress-at-rest-coefficient (K0), defined as the ratio of normal compaction and pre-compaction, was introduced. The objective of this study was to explore the potential of relating K0 with ECa using data obtained from sites with wide ranges of soil texture, bulk density, and water content, properties that significantly affect both CI and ECa. The following data was collected from 35 sites in Missouri and Illinois fields: CI profile up to 75 cm with a 5-cm interval, ECa measured by EM38 and Veris devices, and depth-dependent soil properties such as soil texture, bulk density, and water content. First, K0 values were calculated from CI profiles by depth and related to ECa measurements. Then, effects of the soil properties on the relationships between K0 and ECa were investigated. Results of this study will provide insights on the effects of soil properties on soil compaction, and on the potential to use ECa to estimate the status of soil compaction.