Conventional and organic corn, soybean, and wheat showed no significant differences in yield. Average yields in all crops were at or above the county levels for conventional farmers in both the conventional and organic systems. Initially, conventional-farming corn yields were higher under the conventional production system, but after a 4-year transition period to organic production, there was no difference in overall corn or other crop yields. In drought years, conventional corn yields were significantly lower than in the organic systems.
Soil carbon affects erosion. Increasing soil carbon and enhancing soil aggregation improve soil resistance to wind and water erosion (Troeh et al. 1999). Our study demonstrated that increased mycorrhizal activity under organic cropping systems was a key aggregating agent. Since water either infiltrates or runs off soil, the water percolating through all test crop systems was measured. Data showed that in the organic systems, percolation was enhanced and water runoff decreased. In addition, organic matter increased in the organic systems, whereas no increase occurred in the conventional systems, further confirming reduced erosion in the former.
Avery cites a study by Green and colleagues (2005) to confirm there is no difference between organic farming and conventional farming in terms of soil erosion. There are serious problems in drawing this conclusion from the abstract of the article: There is no information on what type of organic farming system the measurements were made on, and there is no description of how the organic system was farmed.
Although no-till corn has soil conservation merits, it has several costs, including increased pesticide and nitrogen fertilizer use; more weeds, insects, slugs, and voles; and corn seed needs (Troeh et al. 1999). No-till corn requires more fossil energy than conventional culture. In our experiments, the organic corn systems required 30% less energy. Finally, results showed that tillage in organic systems built organic matter at a rate comparable to that of no-till agriculture (Troeh et al. 1999).
