Tillage effects on previously flooded soils

Excessive rainfall inundated many midwestern agricultural fields in 1993 an d resulted in numerous questions regarding the depth and number of tillage operations needed to prepare fields for crop production in 1994. Five on-fa rm locations were selected to compare effects of shallow, moderate, and dee p tillage on soil compaction and crop yield. Bulk density, soil water conte nt (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 1 2 in. averaged 1.27, 1.26, and 1.22 g/cu cm for no-till, chisel, and subsoi led 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 pene tration resistance averaged 378, 341, and 283 psi (LSD(0.05) = 19) for no-t ill, chisel, and subsoiled areas, respectively. Increased preplant tillage intensity significantly affected some soil physical properties, but corn an d 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 s ubjected to excessive rainfall and inundation events like those occurring t hroughout the Midwest in 1993.