Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 1999
Publication Date: October 1, 1999
Citation: Kramer, L.A., Burkart, M.R., Meek, D.W., Jaquis, R.J., James, D.E. 1999. Field-scale watershed evaluations on deep loess soils: II. Hydrologic responses to different agricultural land management systems. Journal of Soil and Water Conservation. 54(4):705-710. Interpretive Summary: Erosion in the Deep Loess Hills of Iowa and Missouri Deep Loess is related to runoff associated with row crop production. Thirty years of data on runoff, groundwater seepage, and sediment discharge were examined at the U.S.D.A. Deep Loess Research Station near Treynor, Iowa. Four watersheds from 68 to 150 acres were studied with different farming management systems. Results of this analysis showed conservation tillage increased infiltration, reduced runoff, and reduced sediment discharge when compared to conventional tillage practices. It was found that conservation tillage reduced erosion most greatly during periods with large storms and during the pre-planting and early crop-growth season when the soil is most vulnerable to erosion. This means that land-management practices like ridge till provide multiple benefits to soil and water management. In addition to reduced erosion, reduced runoff and accompanying increase in baseflow provides additional soil moisture available for crops. This is particularly important in these relatively well drained soils. It was also found that terraces did not offer any substantial erosion control benefit over the conservation practice of ridge till. Farmers and action agencies will benefit from these results in considering the application of conservation practices and evaluating the utility of terraces.
Technical Abstract: The Iowa and Missouri Deep Loess Hills is a fragile region that is susceptible to erosion and disruption of the balance between infiltration and runoff as a consequence of row crop production. Analysis of more than 30 years of runoff, baseflow, and sediment discharge measurements at the U.S.D.A. Deep Loess Research Station near Treynor, Iowa showed conservation tillage improved these important hydrologic responses. These management systems produced smaller amounts of storm-driven runoff and significantly more baseflow resulting from groundwater seepage. Accompanying this change was a significant reduction in sediment discharged annually as well as during peak storm events. Sediment discharge was also reduced during the critical erosion season between spring tillage and development of crop canopy. The watershed with ridge till and terraces did not show as much reduction in runoff and sediment discharge as did the watershed with ridge till but no terraces. While the significance of this relation is not large, it has implications for the efficacy of terraces in this region. It is clear that land-management practices such as ridge till and terracing provide multiple benefits to soil and water management. The reduced magnitude of runoff resulting from maximum storm events decreases the loss of sediment derived from sheet and rill erosion. The reduction in annual runoff and accompanying increase in baseflow provides for additional potential soil moisture available for crops. This is particularly important in these relatively well drained soils.