Quantifying changes in soil physical properties from soil and crop management: A survey of experts

A questionnaire was developed to investigate relationships between soil physical properties and tillage practices. The purpose was to develop a knowledge base which could quantify these relationships and be translated readily into rules for use in the BESTAQUA hydrologic simulation model and expert system. Experts were asked to evaluate the effects on soil physical properties of four tillage practices, two soil types, three times of the season, and one or two soil depths in a corn-soybean rotation. Soil properties included surface crop residue, surface storage volume, macropores which were continuous to the surface, soil organic matter bulk density, saturated hydraulic conductivity, and plant available water capacity. Thirty-two respondents (58% response rate) provided soil property estimates. From these data, means and confidence interval ranges provided a quantitative approximation of the relative expected changes in soil properties with tillage practice, crop year of a rotation, time of season, and soil depth and type. The means and ranges of the relative changes were compared with literature data: and interpreted drawing upon the information-rich qualitative feedback from the experts. Confidence interval ranges of these trends were generally found to span the ranges of values found in the literature and showed that management practices significantly influence soil properties. These results provide a set of reasonable and comprehensive values for estimating the relative effects of tillage management on soil physical properties, and present an opportunity to improve many agricultural hydrologic models and equations by including the effects of tillage-induced soil physical properties changes summarized in this study.