According to the USDA, 15% of Pennsylvania corn had been planted by May 5, and few soybean acres had been planted (National Agricultural Statistics Service). Farmers are therefore anxious to get their corn and soybeans in the ground, but need to watch for sidewall compaction because of high soil moisture content.
On May 5, moisture content in the top 2 inches of the soil was very high (35–40%) in much of the state. Especially in the western part of the state (Soil Moisture Map), and this week calls for more showers.
Sidewall compaction is caused in moist soil by the double-disk openers that open the V-shaped seed slot. The soil on both sides of the seed slot will look glazed and shiny – the soil is compacted around the seed.
The ball test is used to determine if soil is fit for planting: grab a handful of soil to the depth of planting, knead it in your hand, and if you can easily make a ball out of the soil, it is in the ‘plastic state,’ meaning it is easy to cause sidewall compaction. Sidewall compaction causes the seminal corn root system to be constricted. The roots are not able to penetrate the sidewall, and the result can be varied. Reduced early growth that increases susceptibility to drought, pests, and diseases, and deficiencies of phosphorus and potassium.
If dry conditions follow planting, the seed slot can pop right open, exposing the seed to predators and drying. To avoid sidewall compaction, wait until the soil is fit. If you have been practicing soil health improving practices, you will notice that the soil becomes more forgiving, and is not in the plastic state for very long due to better soil aggregation and drainage. You can also reduce down-pressure on the gauge and closing wheels on the planter, use a depth gauge wheel that has a slightly smaller diameter next to the opener disks (so they don’t compress the soil), and use spoked closing wheels to break up the sidewall.
