Submitted to: International Soil Tillage Research Organization Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 3, 2006
Publication Date: September 3, 2006
Citation: Karlen, D.L., Tomer, M.D., Neppel, J., Cambardella, C.A. 2006. Assessing soil quality at a watershed scale in North Central Iowa, USA. 17th International Soil Tillage Research Organization (ISTRO) Proceedings. p.1255-1267.
Soil management decisions can have a direct impact on both soil and water quality. Our objective is to provide an initial assessment of how management practices in the South Fork Watershed of the Iowa River are affecting several soil quality indicators and overall soil quality. Soil samples were collected during autumn 2003 and spring 2004 from 29, 65-ha areas along two transects traversing the South Fork Watershed. Several soil quality indicators were measured and four (pH, electrical conductivity (EC), total organic carbon (TOC), and soil-test P) were used to compute a soil quality index (SQI) using the Soil Management Assessment Framework (SMAF). The RUSLE II simulation model was used to compute Soil Tillage Intensity Rating (STIR), soil loss, N leaching potential, and the Soil Conditioning Index (SCI) for each sampling area. Soil-test P levels were often high or very high with regard to crop needs, but not to the point where the SMAF scoring functions would indicate an environmental risk. Low soil-test K could be an agronomic concern if no-tillage is adopted throughout the watershed. Soils in upper landscape positions had lower organic carbon and C:N ratios that could increase the risk for nitrate leaching. The SCI and SQI were positively correlated and indicate that soil quality is relatively stable for the management practices being used throughout the watershed.