Dan Quinn, Ph.D.
Assistant Professor of Agronomy
Extension Corn Specialist
As planting dates continue to get pushed earlier and spring weather conditions become more variable, the chance that corn is planted into less than ideal soil conditions increases. Sidewall compaction can occur when planting is performed under soil conditions that are too wet.
Why is Sidewall Compaction Important?
Sidewall compaction refers to soil compaction and soil smearing in and around the seed furrow which can result in restricted root growth, poor emergence, and lost yield potential. Once sidewall compaction occurs at planting, it cannot be cured. Sidewall compaction can haunt you throughout the entire growing season by limiting emergence, root growth, nutrient uptake, yield, and increasing the chance for lodging prior to harvest. Therefore, taking the necessary steps to prevent sidewall compaction during planting is important.
What Causes Sidewall Compaction?
Wet soils are easily compacted and planting corn into these conditions is the biggest contributor to sidewall compaction. Planter seed furrow openers can smear and compact the sides of a seed furrow when planting occurs too wet, especially if too much down pressure has been applied. When this occurs, the soil in the seed furrow does not properly break and fall around the seed for adequate seed-to-soil contact, and root growth becomes restricted. Sidewall compaction can also occur when corn is planted too shallow. When corn is planted too shallow and soils are too wet, compaction can also occur below the seed, thus making it difficult for corn roots to penetrate the soil.
How to Identify Sidewall Compaction?
In addition to early season scouting for disease, pests, and nutrient deficiencies, it is also important to scout fields for potential compaction issues. Sidewall compaction can result in non-uniform emergence, stunted plant growth, and nutrient deficiency symptoms despite adequate soil nutrient levels due to poor root growth. Proper diagnosis of sidewall compaction can be performed by digging corn plants in problem areas and examining the roots. A healthy corn root system should have adequate and uniform vertical and horizontal root growth all around. However, if the majority of the corn roots exhibit only vertical growth and poor horizontal growth, as indicated by Image 1, this can be an indicator that roots could not penetrate the sides of the seed furrow due to compaction. In addition, it is also important to examine the seed furrow following planting and look for smooth or shiny surfaces within the furrow which can indicate that smearing and compaction occurred. Furthermore, areas within the field with open seed furrows and poor seed-to-soil contact can also be indicators of sidewall compaction.
Image 1: A) Cross-view of corn roots looking across the row and B) cross-view of corn roots looking with the row. Roots are exhibiting poor and non-uniform growth due to sidewall compaction at planting.
How to Prevent Sidewall Compaction?
Preventing sidewall compaction starts with planting into optimal soil moisture conditions and maybe waiting an extra day or two for the soil to dry further. However, this may be easier said than done when spring planting is delayed. Other considerations for preventing sidewall compaction include: adjusting downforce pressure on row-units to specific soil conditions, reduce closing wheel downforce, avoiding shallow planting and target a 2-inch seeding depth, and utilizing a spiked closing wheel to till in the sidewall and improve seed-to-soil contact.