Use of a Technical Soil Classification System in Evaluation of Corn and Soybean Response to Deep Tillage

Crop response to soil management practices is determined in part by soil properties. Soil classification systems provide a readily available measure of soil properties. If information about crop response to soil management practices can be transferred between locations based on soil classification information, this will aid in the adoption of optimum management practices. As a test of the usefulness of soil classification information in transfer of response information, a technical soil classification system was used to evaluate corn (Zea mays L.) and soybean (Glycine max L. Merr.) response to deep tillage across a range of soil, climate, and management conditions. Three deep tillage systems—subsoiling under the row, subsoiling under the row plus bedding, and chisel plowing—were compared with a shallow tillage system, disking only, in 16 experiments with corn and 13 with soybeans on North Carolina farms. Soils in the fields were classified according to a technical soil classification system adapted from the Fertility Capability Classification (FCC) system. Response to deep tillage varied significantly among soil groups in the technical classification system. Yield increases due to deep tillage varied by soil group from 36 to 3% with corn, and from 25 to −2% with soybeans. A general recommendation based on results across all soils would have led to nonoptimum choices of tillage practices on half of the soil groups. Response was related to texture and thickness of Ap and E horizons, and texture of Bt horizons. The largest yield increases occurred on soils with sandy Ap and E horizons over loamy Bt horizons. No significant yield responses occurred on soils with loamy Ap horizons overlying clayey Bt horizons. The technical soil classification system was found to have considerable potential as a basis for transfer of tillage response information.