With little or no reserve supply of moisture in the subsoil in much of Iowa this fall, farmers need to ask themselves: Do I need to be doing any tillage at all this fall?
Farmers should consider no-till farming as the most important tool to prevent loss of soil moisture, especially during the current drought conditions in Iowa, advises Barb Stewart, state agronomist with the USDA-Natural Resources Conservation Service in Iowa.
“Drought management is a top concern right now. With the drought conditions continuing in Iowa, and across the Midwest, many producers are concerned about the next planting season," she notes. “And with the extremely early harvest, many producers have more time on their hands to go out to the field and do soil tillage operations. NRCS is recommending farmers use that time for something else more productive."
How does tillage reduce soil moisture? Several ways and they all add up
Soil tillage reduces soil moisture in several ways. The first is reduced water infiltration. Tillage reduces water infiltration by breaking up the large pores in the soil structure, which act as large diameter pipelines for water to soak into the soil profile. Removing residue through tillage operations also leads to more soil erosion. The eroded particles of soil can then clog the smaller pores or pipes, further preventing infiltration and causing more soil runoff.
“Iowa State University research shows that initial water infiltration rates are reduced from 5.67 inches per hour under no-till farming to 2.60 inches per hour under a soil tillage system," says Stewart.
Other reasons to consider no-till farming as a great soil moisture management tool include:
* Every tillage pass can cause available plant moisture to drop .25 inch.
* Crop residue moderates soil temperatures, reducing soil moisture evaporation, especially in the top 2 inches.
* Cornstalks can help trap snow, which can add up to 2 inches of soil moisture after snow melt in the spring.
Stewart says many concerns farmers use to justify soil tillage are minimal this year. “Under the dry conditions we've had in 2012 and continue to experience this season, soil compaction due to equipment traffic was minimal," she points out. “Additionally, Gross's wilt, a corn disease that was a fairly widespread problem in Iowa in 2011, was not an issue in 2012. So there is no need to use tillage to try to minimize the risk for that disease," she said.
Farmers concerned about their soil moisture supply should visit their local NRCS office to discuss methods to help conserve and enhance the water holding capacity of their soils. Some of these practices include no-till, strip till and cover crops.