Submitted to: Bioscience
Publication Type: Other
Publication Acceptance Date: 5/12/2006
Publication Date: 6/20/2006
Citation: Green, V.S., Cavigelli, M.A., Dao, T.H., Flanagan, D.C. 2006. Letter to the editor. Care needed in comparisons. Bioscience. 56:461. Interpretive Summary:
Technical Abstract: Our research results were cited in a letter to the editor of BioScience by Alex Avery to challenge the conclusions of a paper written by David Pimentel and colleagues. In this letter we address some of the comments made by both Avery and Pimentel and co-workers. As Avery states, we concluded that soil erosion potential is essentially equal in chisel-till and organic cropping systems based on soil aggregate size class distribution data, and that soil erosion potential in both is considerably greater than in a no-till cropping system. We also used the Water Erosion Prediction Project model, which takes the entire crop rotation cycle and management practices into consideration, to predict soil erosion among the three cropping systems. Results of 100 year erosion simulations show that while predicted soil loss in the no-till system (8.5 Mg ha-1 yr-1) was much lower than in the other two systems, predicted soil loss in the organic system was about two thirds that in the chisel- till system (43 and 64 Mg ha-1 yr-1, respectively). Lower predicted erosion in the organic system compared to the chisel-till system using WEPP is due to greater use of winter cover crops in the organic system, despite greater tillage in the organic than in the chisel-till system. Additional long-term agricultural trials that include locally-relevant organic and conventional cropping systems on diverse soil types and in diverse climates are needed to fully assess the sustainability of organic and conventional farming systems. It is important to recognize that many organic farmers and researchers who study organic farming systems are fully aware of the benefits of reducing tillage in organic cropping systems and are working to develop cropping systems that both reduce soil erosion and minimize the impacts of agricultural activities on the environment.