The planting delays and wet soil conditions will increase the potential for sidewall compaction to occur. Sidewall compaction includes all soil compaction and soil smearing in and around the seed furrow, and can restrict root growth and reduce crop yields. Sidewall compaction typically occurs when planting into soils that are too wet, planting too shallow and setting too much down pressure on the gauge wheels and closing wheels. Sidewall compaction is never beneficial and will be the most detrimental when the soil becomes dry after planting.

The most effective way to prevent sidewall compaction is to wait until soil moisture conditions are suitable for planting. This is easier said than done given the calendar date and planting delays we are experiencing. There are several methods for determining if the soil is too wet to plant. Mark Hanna, agricultural engineer at Iowa State University, recommends the following methods for assessing planting conditions:

• Collect a handful of soil from the top 2 to 3 inches and form it into a ball. Then throw the ball of soil as if throwing a runner out at first base. If the ball stays mostly intact until it hits the ground, the soil is too wet to plant.
• Take a similar soil sample in your hand and squeeze the soil in your fist and use your thumb and forefinger to form a ribbon of soil. If the ribbon extends beyond 3 inches before breaking off, the soil is probably too wet to plant.

You can also evaluate how the planting equipment is operating in the field. If soil is building up on the rubber closing wheels, the soil is too wet to plant. You should inspect the sides of the seed furrow periodically for signs of soil smearing (a smooth, shiny appearance). Check to make sure that the seed furrow is closed while using minimal down pressure on the closing wheels.

Paul Jasa, agricultural engineer at the University of Nebraska, provides some excellent recommendations for reducing sidewall compaction when planting into less than ideal soil moisture conditions in the following articles: “Tips to Reduce Sidewall Compaction” and “Avoid Sidewall Compaction with Planter and Planting Adjustments.” A few of Jasa’s recommendations are listed below:

• Reduce the down pressure on both the gauge wheels and closing wheels.
• Try to leave some crop residue over the row to delay soil drying and opening of the seed furrow.
• Level the planter from front to rear or possibly operate it slightly tail down to improve seed-to-soil contact and seed furrow closing.
• Consider adding one spoked closing wheel per row. This will break up the sidewall compaction on one side of the furrow and close the seed furrow more effectively.
• Staggering the closing wheels will reduce the potential for the seed furrow to open up as the soil dries. If using one spoked wheel and one standard rubber wheel, place the spoked wheel in front.