September 29, 2016 

How to Minimize Soil Compaction During Harvest

            Harvest is one of my favorite times of year. Watching fields being harvested as I drive to and from work each day takes me back to my days of growing up on a farm in the Platte River valley. One big difference is our soils were sandier and less prone to compaction than most of the soils in our area. I remember the urgency we felt to get out and start harvest as soon as we could.

            Most areas received surplus rain in September, a time when corn and soybean water use declines significantly. This lack of water use by the plant creates saturated soils susceptible to compaction this fall. High soil moisture increases soil compaction caused by field traffic and machinery. Over the past decade the size of farms has increased, leading to larger and heavier equipment. However, equipment size is only one factor among many causes of the soil compaction problem.

            Rushing to the field when the soil is wet can increase chances for severe soil compaction, combined with the weight of equipment and traffic pattern in the field. Maximum soil compaction occurs when soil moisture is at or near field capacity because soil moisture works as a lubricant between soil particles under heavy pressure from field equipment.

            Here are the top 10 reasons to avoid soil compaction:

  1. Causes nutrient deficiencies

  2. Reduces crop productivity

  3. Restricts root development

  4. Reduces soil aeration

  5. Decreases soil available water

  6. Reduces infiltration rate

  7. Increases bulk density

  8. Increases sediment and nutrient losses

  9. Increases surface runoff

10. Damages soil structure

            So what should you do? Here are four management decisions to minimize soil compaction during and after harvest.

            Dedicated travel lanes. Many combine operators use “on-the-go” unloading into a grain cart to speed harvest. In areas that received excessive rainfall in September, you may want to consider either having dedicated travel lanes in and out of the field for the grain cart. Also, be sure the grain cart wheels are in the same rows as used by the combine. The second pass over the same soil contributes less to compaction than driving on new soil in different rows.

            Another option is not loading a large cart to full capacity. This may not be an attractive option in high-yielding corn fields, but could be more easily implemented in soybeans where the volume of crop being removed from the field is much less. For those using grain carts with 1,000 bushel capacity or greater, axle load from a single-axle grain cart will be greater than the weight on the front combine axle.

            Tire size. Properly adjusted tire size and correct air pressure for the axle load being carried is a second management tool. Larger tires with lower air pressure allow for better flotation and reduced pressure on the soil surface. Additionally, using larger tires that are properly inflated increases the "footprint" on the soil.

            Check soil moisture. The most effective way to minimize soil compaction is to avoid field operations when soil moisture is at or near field capacity. So it is important to check soil moisture conditions prior to implementing any harvest or tillage operation.

            Most of our soils have medium textures. For these soils, a simple method to check soil moisture is the "feel" method. Probe the top three to four feet with a hand soil probe to assess the field's soil moisture conditions.

            Check the soil moisture by pushing a ribbon of soil from between the thumb and index finger. If it breaks off within one or two inches, the potential for creating compaction is less. However, if the ribbon stretches out to four or five inches, it is still too wet. The chances are good that being in the field under these conditions may cause more problems than it will solve. Waiting an extra day or two can reduce soil compaction significantly.

            Reduce tillage. Remember to hold off tillage operations until soil conditions are drier than field capacity and remember the benefits of conservation tillage systems. In wet conditions, the best choice producers can make is to stay away from the field and avoid traffic on wet soil to reduce soil compaction. How you approach fieldwork after a heavy rain event can impact your soil for future growing seasons.

            One final benefit or staying out of fields when it is too wet is not creating ruts that will require tillage to fill in before planting next spring, or worse yet, having a picture of your combine or tractor buried to the axle circulating on the internet or posted on Facebook for all your friends or neighbors to see.