Abnormally wet soils in many areas during the late harvest combined to create soil compaction issues in many fields. Soil type and condition of the soil are two of the main factors contributing to the degree of compaction. Soils with low organic matter, clay or even some sandy soils tend to be more susceptible to compaction; however, any soil type can become compacted when soil water content is high.
Diagnosing the severity of soil compaction
There are several methods that can be used to determine the extent of compaction. One of the easiest is to drive a steel or wooden stake at least 18 inches into an area that has not been tilled or driven over for several years, such as a fencerow, and then drive the same stake into an area of suspected compaction. Count the number of hammer blows exerted, along with the relative ease or difficulty of each swing to gauge the level of compaction. This simple test aside, many farmers are adept at recognizing compaction with simple observation.
Steps to minimize compaction
The most effective way to avoid compaction is to keep heavy equipment off fields when soil conditions such as excess moisture are prevalent. In years like 2019, however, with harvest already delayed, keeping out of the field wasn’t a desirable option. Yet, delaying field work for even a portion of a day to allow for additional drying made a big difference.
Reducing load weights on grain carts, wagons, etc., can make a big difference when traversing wet fields. Recognizing that unloading combines on the go is more efficient, doing so adds to the number of trips across the field with a full cart, further increasing the frequency and severity of compaction. When possible, consider having grain carts and semi-trailers remain at one spot at the end of the field to help reduce the surface area affected by compaction.
Since the greatest amount of compaction occurs on the first trip across the field, controlling traffic is important for managing soil compaction. Controlling traffic will lead to slightly deeper compaction in the tracked area, but the soil between the tracks won’t be affected, hence the area of compaction will be minimized. If you use GPS, no-till, strip-till, etc., you can confine traffic between the compacted row area by properly matching all machines (combines, grain carts and manure equipment) to the same between-row areas. Driving equipment diagonally across a field should be avoided entirely as doing so creates multiple wheel track patterns at a deeper compaction level.
Compaction and rut repair
Before returning to the field after harvest, evaluate the condition and moisture. Continuing operation on wet and rutted fields will only further compact the problem further and will likely negatively impact next year’s yield. Wait for soils to dry or freeze before continuing field work or consider waiting until spring to fill ruts and till compacted areas. Depending on the severity of compaction, you may even want to consider alternative practices for next year’s crop, including reducing tillage passes or going without tillage for a year. If you forego tillage, you’ll need to adjust your planter for high-residue fields.
In some soils, deep compaction could be naturally alleviated by soil cracking over the summer, if dry conditions persist. Cracking can help improve compaction several feet below the soil surface and is much more effective than free-thaw cycles or mechanical methods. Using mechanical means, such as deep ripping, is unreliable and can often result in poor or detrimental results related to smearing and breaking down soil structure.
For more information on how to effectively manage compaction, contact your university Extension agent or ag retailer.
Find additional information at https://www.extension.purdue.edu/extmedia/AY/AY-221.html and https://extension.umn.edu/soil-management-and-health/soil-compaction.