Signature was redacted for privacy.Signature was redacted for privacy. Signature was redacted for privacy. 157 VIII. ACKNOWLEDGMENTS 165 IX. APPENDIX 166 iv LIST OF TABLES Page 157 VII. LITERATURE CITED Aandahl, Andrew R. 1948. Characterization of slope positions and their influence on the total nitrogen content of a few virgin soils of western Iowa. Soil Sci. Soc. Am. Proc. 13:449-454. Adams, John E., Kirkham, Don, and Scholtes, Wayne H. 1958. Soil erodibility and other physical properties of some Iowa soils. Iowa State College J. Sci. 32:485-540. Aikman, J. M. 1941. Effect of aspect of slope on climatic factors. Iowa State College J. Sci. 15:161-167. Alderfer, R. B. and Merkle, P. G. 1941-Measurement of struc tural stability and permeability and the influence of soil treatments upon these properties. Soil Sci. 51: 201-212. Anderson, M. A. and Browning, G. M. 1949. Some physical and chemical properties of six virgin and six cultivated Iowa soils. Soil Sci.
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/m2 retarded 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.
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