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Corn was grown for 3 years on Wooster silt loam, a soil on which the yield response of corn to cultivation exceeds that attributable to weed control. Treatments included conventional preplant tillage (plowing, disking) and no preplant tillage with three corn stover residue levels, 5% cover (stover removed), 45% cover (stover left in place), and 70% cover (double level of stover). Except for the first year when the tilled plots were not cultivated, grain yields with 45% cover (6,170 kg/ha) equalled the tilled check (5,970 kg/ha). Yields of treatments with 5% cover were significantly lower (4,770 kg/ha) than the tilled treatment and significantly higher with 70% cover (6,625 kg/ha). Soil moisture determined with gypsum blocks during the last 2 years was greater with increasing amounts of soil cover during the growing season. Soil cover did not increase during the experiment, even on treatments receiving double residue. At the end of the third year, water infiltration as determined with a sprinkling infiltrometer was significantly greater with 80% cover than for the other treatments. Results from these experiments indicate that mulch protection which may be readily available from previous crop residues is necessary to maintain no‐tillage corn grain yields on this and similar areas of Wooster silt loam. The beneficial effects of the mulch seem to be associated with increased soil moisture.

Measurements of original and present surface soil depth, as indicated by slope and erosion field data and organic carbon contents, were used to determine the relative erodibility of the loess‐derived Monona, Marshall, and Sharpsburg soils in southwestern Iowa. These studies indicated decreasing surface soil depths with increasing slope on all three soils, with the Monona soil having the least and Sharpsburg the most surface soil remaining. The difference in average depth to an arbitrary benchmark, 0.90% organic carbon content, in cultivated as compared with virgin profiles of each soil indicated, however, that slightly lower erosion losses due to cultivation over time have occurred on the Monona soil. Laboratory rainfall simulator studies indicated higher infiltration and lower soil loss rates on the Monona soil than on the Marshall and Sharpsburg soils. The formation of a dense surface seal by raindrop impact appeared to be a dominant factor in the erodibility of these soils. Studies on crusted samples indicated slightly lower soil loss and higher infiltration rates on the Monona even with the crust present.

Various concentrations of a corn steep liquor slurry were compared with straw mulch for erosion control and vegetative establishment on highway backslope plots. Applications of 5 and 10% corn steep liquor slurry followed immediately with lime slurry formed a thin, stabilized surface layer that resisted initial erosion on backslope plots after seeding. However, plant growth, cover, and erosion control over a growing season were the greatest under straw mulch, with no significant differences noted from the various corn steep liquor treatments by the end of the season. Growth chamber studies showed corn steep liquor slurry concentrations of over 10% solids applied at 1.4 liters/m2retarded emergence of tall fescue seedlings up to 1 week. Soil moisture evaporation losses in a greenhouse study were not significantly affected by various rates of corn steep liquor application, but were greatly decreased by straw mulch.