ABSTRACT:
The 1987 National Resources Inventory (NRI) was used to provide a random sample of 100 Illinois cropland sites growing corn and soybeans. These were used with the Erosion Productivity Impact Calculator (EPIC) model to simulate responses of soil erosion and nutrient exports to several different tillage and crop rotation practices. The NRI and other data sources were used for site specific characterizations that reflected the multidimensional variability in site conditions in Illinois. Four alternative management schemes were simulated for each site: continuous corn and soybean/corn rotations under conventional tillage and no-till. Average crop yields varied little under the four management schemes and closely corresponded to expected yields from the SCS Soils-5 Soil Interpretation Records. However, no-till significantly reduced soil erosion rates and loss of soil organic carbon compared to conventional tillage. This reduced erosion under no-till also led to reduced losses of nitrogen (N) and phosphonw (P) in eroded soil. Percolation belous the root zone represented the greatest N export and is of concern for the issue of groundwater contamination in this region. Nitrate N concentrations in percolate substantially exceeded the drinking water standard of 10 mg/l. Soybean/corn rotations generally had 10–30 percent lower soluble N losses in surface runoff, subsurface flow, and percolation than the corresponding conventional tillage or no-till practices under continuous corn. No-till resulted in a 24 percent increase in soluble N runoff losses compared to conventional tillage in soybeadcorn rotations. P losses in surface runoff were larger under no-till, likely as a result of the lack of immediate incorporation of surface P fertilizer into the soil. The model predictions for changes in soil erosion and N and P losses under different management practices were in line with measured changes in site-specific field studies under similar conditions. Our study results take into account the effect of site-to-site variability on the responses and the relative frequency of different site conditions state-wide. This indicates the potential magnitude for changes in nonpoint source pollution by sediment, N, and P state-wide by adoption of alternative corn and soybean tillage and rotation schemes.
Footnotes
Donald L. Phillips is a research biologist with the I. T.S. EPA, Cowallis, OK 9233.3. Paul D. Hardin and Joseph V. Raglio are GIS specialists with Manskch Environmental Technology Inc., Cowallis, OR 9 733.3. Verel W. Benson is an agricultural economist with the SCS, Temple, 76502. The research described in this article has been funded by the U. S. EPA. This document has been prepared at the EPA Environmental Research Laboratory in Corvallis, OR, through contract #68-C8–0006 to ManTech Environmental Technology, Inc. It has been subjected to the Agency's peer and administrative review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. We gratefully acknowledge the assistance of Richard Dickevson (SCS-Illinois) for assistance with the management scenarios. Jeff Lee (EPA), Thyrele Robertson (SCS); Jeff Goebel (SCS), and three anonymous reviewers for reviewing the manuscript; Lew Ladd for computer programming support; the U.S. EPA Office of Policy, Planning, and Evaluation for financial support; and Richard Olson, for prompting the initiation of this study.
- Copyright 1993 by the Soil and Water Conservation Society
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