Fall tillage in wet soil conditions
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When there’s heavy precipitation in the fall, harvest in Minnesota can be challenging. Farmers need to consider how to get in the field to harvest, and if they’ll have time to complete fall tillage.
Strategies for success
Soil compaction and smearing is a concern when pulling implements through or driving on wet soil. Residue management is another concern.
Consider the following strategies to limit soil damage and help fields quickly warm up and dry out in the spring for quick planting.
If you have ruts in the field from fall harvest, the first instinct is to aggressively fill them in. Soil structure is your soil's number one defense against future soil compaction, and tillage destroys structure.
To maintain your soil’s structure, fill in the ruts with light tillage by running equipment at an angle. You may need two to three passes to accomplish this. These areas won’t yield as well as the non-rutted area, but there’s not much you can do to change this.
Options: Disking and vertical tillage
A light tillage pass, like disking, is useful for incorporating residue and introducing air into the soil. If the soil is wet, try to operate this shallow tillage equipment no deeper than 3 inches.
Another option for wet soils is vertical tillage (Figure 1). Vertical tillage runs 1 to 3 inches deep and uses straight or wavy coulters, a harrow and rolling baskets. Vertical tillage fluffs up the remaining residue with shallow penetration and minimal inversion of the soil.
Lifting wet soils can create clods. If you’re 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. Twisted or parabolic shanks create the most soil movement and can create soil clods.
Clods in themselves aren’t bad going into winter. Next spring they’ll leave more surface area for water infiltration. However, a field with clods will likely need an extra tillage pass in the spring to create an adequate seedbed for good seed-to-soil contact.
Another consideration is “frost tillage,” a phrase coined by Harold van Es and Robert Schindelbeck in 1993 when researching tillage on a slightly frozen soil in New York. The premise was, as the soil surface freezes, it pulls or wicks moisture from the lower layers of soil, making them drier.
Compared to no frost, they found when the frost layer was 0.5 to 1 inch:
The soil better supported the equipment’s weight when chisel-plowing to a depth of 8 inches.
The soil below the frost layer was drier and tilled easily.
Corn yields weren’t affected.
Rain infiltrated quicker in the tilled soil versus a soil without tillage. This is due to the frozen plates of soil created with frost tillage. As these plates thawed, they quickly diminished.
While Minnesota usually doesn’t have the shallow frost cycles throughout the winter like New York, we generally have at least one or two freeze-thaw cycles each fall.
In the fall of 2007, we ran a strip tiller through 1.5 inches of frost and the machine worked very well. However, due to horsepower limitations, tillage may not be practical when the frost is much deeper. The shallow frost provided an opportunity to extend our fall tillage window.
Reduce weight and maintain air pressure
Wet soils (Figure 2) have a high potential for soil compaction. To limit soil compaction, keep axle loads under 10 tons and properly maintain air pressure in the tires.
This helps the soil, plus it’ll help your tractor run more efficiently and with less slippage. On wet soils, use the lightest tractor that can still get the job done.
There isn't much you can do to reduce the weight of combines. If possible, unload before the grain hopper is full to limit axle loads. Large grain carts have very high axle loads (up to 43 tons per axle).
Control wheel traffic
Control the wheel traffic from grain carts by running in the previous combine tracks and don't cross the field at a diagonal. Eighty percent of the compaction happens on the first pass; use it to your advantage.
Check over equipment and replace worn parts, sharpen blades and adjust down pressure for each field's soil conditions. These small details are more important in extreme moisture conditions.
Wet conditions can lead to a challenging fall harvest. Keep your options open, as things can change quickly.
Planting soybeans may be the best option in fields with heavy residue. They are very adaptive to higher residue levels, aren’t as sensitive to soil temperature as corn, and grow well in no-till situations. If trying no-till soybeans, set the combine’s corn header as high as possible to reduce the amount of residue matted onto the soil surface.
Corn on corn has more residue to manage and needs additional nitrogen fertilizer than corn following soybean. Row cleaners are a must for corn following corn to get uniform seeding depth and help warm the soil over the seed. If there are high quantities of surface residue, consider a starter fertilizer for corn following corn.
Wheat is another option for heavy-residue fields. However, if you’re planting wheat after corn, choose a variety that minimizes the potential for diseases.
Reviewed in 2018