Choose fall tillage method based on soil conditions
ST. PAUL -- Fall tillage decisions became a lot more complicated because of the heavy rains in September. Flooding and the prospects for another wet harvest season will make effectively using tillage to manage residues more difficult. University of Minnesota Extension research can provide some guidance
In a dry fall, there are more options for residue management, and deeper tillage will have less negative effect on the soil. Even so, different implements have differing effects on soil structure and residue incorporation. Chisel plows have more of a lifting effect on the soil and the soil tends to fracture along natural plains. Extension research shows that chisel plows can incorporate about 50 to 70 percent of the residue.
A disk has more down pressure. The smearing and shearing effect breaks apart more soil structure than chisels. However, disks are very effective at cutting and sizing residue for decomposition, making planting easier in the spring. Depending on the shape and size of the disk, 40 to 80 percent of the residue is incorporated.
If your fields are wet during harvest and ruts are created, the first instinct is to aggressively fill them in. To protect the existing soil structure, just fill in the ruts with light tillage by running equipment at an angle. You may need two or three passes to accomplish this. These areas will not yield as well as the non-rutted area, but there is not much you can do to change this.
When the soils are wet and residue management is the main issue, a light tillage pass with a vertical-till implement is useful for sizing and incorporating some residue and introducing air to the soil. Vertical tillage runs 1 to 3 inches deep and uses straight or wavy coulters, a harrow, with rolling baskets being optional. Vertical tillage fluffs up the remaining residue with shallow penetration and minimal soil movement.
Lifting wet soils can create clods. If using a chisel plow or disk ripper, shallow up the shanks, and use narrow points. The wings have a higher potential for smearing the soil. Clods in themselves are not bad going into winter; they will leave more surface area for water infiltration. However, a field with clods is more difficult to break apart and may need multiple tillage passes in the spring to get ready for planting.
Keep your options open as things can change quickly. Visit the tillage page on the University of Minnesota Extension website at www.extension.umn.edu/tillage for more information.
Jodi DeJong-Hughes is a crops educator with University of Minnesota Extension.