Tillage effects on previously flooded soils

Excessive rainfall inundated many midwestern agricultural fields in 1993 and resulted in numerous questions regarding the depth and number of tillage operations needed to prepare fields for crop production in 1994. Five on-farm locations were selected to compare effects of shallow, moderate, and deep tillage on soil compaction and crop yield. Bulk density, soil water content (theta(v)), penetration resistance, and yield of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] were measured, and net return was computed for the three tillage treatments. Preplant bulk density within the upper 12 in. averaged 1.27, 1.26, and 1.22 g/cu cm for no-till, chisel, and subsoiled treatments, respectively. Penetration resistance averaged 130, 120, and 97 psi for the no-till, chisel, and subsoil treatments, respectively (LSB(0.05) = 7), and showed highly significant differences at depths from 0.5 to 12 in. Post-harvest bulk density was not significantly different, but penetration resistance averaged 378, 341, and 283 psi (LSD(0.05) = 19) for no-till, chisel, and subsoiled areas, respectively. Increased preplant tillage intensity significantly affected some soil physical properties, but corn and soybean yields were not affected. With regard to return on investment and time, we conclude it would be more profitable to limit tillage in fields subjected to excessive rainfall and inundation events like those occurring throughout the Midwest in 1993.