Tillage-induced changes in physical properties of a clay loam and corn growth after conversion from alfalfa

Breakdown of soil structure under row crop production negatively affects soil physical properties, thereby reducing crop growth potential and increasing the potential for negative environmental impacts. This is especially of concern in soils with high clay content which depend on good aggregation for favorable hydraulic and mechanical properties.; An experiment with two treatments, plow till and no-till, was conducted on Kingsbury clay loam soil for two years to study soil degradation effects on soil physical properties and corn growth after conversion to row cropping. Two simulated rainfall treatments were applied on 1m{dollar}sp2{dollar} microplots. Undisturbed soil cores were collected from different positions and depths, and used for laboratory determination of soil matrix and pore system properties. Soil physical properties and plant growth parameters were measured in the field.; Favorable soil moisture conditions resulted in good tilth in 1992 while marginally dry soil resulted in large clods in 1993 upon tillage. Spectral analysis of soil strength indicated a basic soil aggregate size of 3-4 mm, although its use for studying soil structure in aggregated soils appeared limited. Soil water content and soil temperature were higher under no-till compared to plow till in 1992 when aggregate arrangements were different, but equal when those were similar in 1993. Soil strength in the surface layer was independent of soil water content, but increased with drying in the subsoil. Rooting patterns revealed that the use of 2MPa penetrometer resistance as a limit for root growth in aggregated soils may be misleading. Root growth was limited under trafficked zones. In contrast to research concluded in the Northern Corn Belt, plant density and height were higher under no-till in 1993, which is attributed to the coarse aggregation in this soil. Other crop growth indicators were not different between tillage treatments. Favorable soil properties under plow till resulted in higher root water uptake and corn yield in 1992, compared to similar yields between tillage treatments in 1993.; Stable structure of this soil indicated a potential for long-term cropping, although post-tillage soil conditions and crop performance may be negatively affected by inappropriate timing of tillage.