Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/1999
Publication Date: N/A
Interpretive Summary: Soil quality indexes have been proposed as tools to help evaluate the effects of various soil and crop management practices. In this manuscript, a simple index used previously to evaluate the effects of tillage on land that had been enrolled in the Conservation Reserve Program (CRP) in Iowa was modified several ways to determine if it was sensitive to changes occurring in southern Illinois soils due to various tillage treatments. Our results showed that the use of no-tillage practices maintained crop residue cover, organic carbon, and aggregate stability. These measurements mean that by using no-tillage practices for crop production, farmers can improve a soil's ability to resist erosion and to provide nutrients for subsequent crops. The use of soil quality indexes helped combine information obtained by measuring several indicators into a tool that could easily be used to help improve decisions related to soil management. We also showed how the proposed index could be modified to increase sensitivity to local and regional management practices.
Technical Abstract: Sustainability of agricultural management systems has become an issue of wide public concern and international debate. One result is that soil quality assessment has been suggested as a tool for evaluating sustainability of soil and crop management practices. Our objective was to adapt a soil quality index to assess the effects of three long-term tillage systems on sloping Grantsburg silt loam soil in southern Illinois. Modifications to the index included changing the weighting factors for the various soil processes, threshold limits for the various measurements, and type of scoring function used to normalize the various types of data. Estimates of air-filled porosity were also added to the nutrient cycling and rooting functions. Changing threshold limits and the type of scoring function used for surface residue data improved the correlation between water relations and soil loss. The addition of porosity indicators increased the sensitivity of nutrient and rooting relations to crop yield and cone index, respectively, and resulted in a better correlation between porosity indicators and plant population. Computing soil quality indices helped to combine different soil properties and processes into a simple tool that explained changes in complex soil properties in response to different tillage practices. Our results demonstrated that adjusting threshold limits for local conditions can make the soil function ratings more or less sensitive to the management practices being evaluated.