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Fall Tillage
by LuAnn Rolling, NRCS District Conservationist
We ended up with an earlier than usual fall harvest, this is a good thing. Using this window to till the soil is not a good thing.
Tillage degrades soil structure, causes erosion and compaction, kills earthworms and destroys the soil ecosystem. Tilling the soil is the equivalent of an earthquake, hurricane, tornado, and forest fire occurring simultaneously to the world of soil organisms. Simply stated, tillage is bad for the soil.
There is a common belief among many farmers and agronomists that tillage can accelerate residue breakdown by the cutting of crop residue into small pieces or burying residue in the soil profile. Also, there is the belief that the application of nitrogen fertilizer on crop residue after harvest can speed up the process of residue breakdown.
Both assertions are not correct.
According to Mahdi Al-Kaisi, Professor of Soil management/environment, at Iowa State University, tillage can contribute to soil health and water quality deterioration by increasing soil erosion potential, sediment loss, and fall N applications result in water quality risks. Residue decomposition is controlled by biological processes that are influenced by environmental and soil conditions. His research, and many other studies, do not support these practices regardless of the justification or claims that propose tillage equipment can manage residue. Disturbing the soil does not constitute an improvement in soil health nor increase in residue decomposition.
Al-Kaisi refers to biological processes being impacted by tillage. Many of the soil organisms influence crop access and uptake of essential plant nutrients. Carbon is a common link or foundation for all of the microbial life in the soil. We know that as we build soil organic carbon, the nutrient cycling of essential plant nutrients improves. No-till significantly increases soil biological health when compared to conventional tillage.
At a recent forum on agricultural production at the Federal Reserve Bank of Chicago, the finance industry was also discussing the economic aspect of no-till and improved soil health. The cited studies found:
• yield improvements of 2%-15% that were attributable to soil health practices;
• The annual change in per-acre net income demonstrated in 3 case studies was $42 per acre per year.
• Their average return on investment for soil health improvements was 169%, ranging from 35% to 343%.
• They were saving $18 to $35 an acre on machinery, fuel and labor costs
• They were saving $17 to $66 an acre per year on fertilizer costs, especially with phosphorus and potassium applications.
