Faced with wet soil this spring, you don't want to plant when it's too wet. "But once you do get into the field, pay attention to the amount of weight being transferred from the planter frame through the parallel links to the individual row units," advises Mark Hanna, Iowa State University Extension ag engineer.
"Use only enough down-pressure on depth-gauge wheels to ensure that they stay in contact with the soil surface. In wet soil conditions, excess load transferred to depth-gauge wheels beyond the point where they firmly touch the soil simply adds more potential compaction to the seed zone. Compacted soil in the seed zone can make it more difficult for seedling roots to penetrate, particularly if subsequent weather allows soil to become dry and hard."
Don't add too much down-pressure
Hanna recommends that you also adjust the spring pressure on closing wheels to a relatively light setting, using only enough down-pressure on the soil to establish seed-to-soil contact. Too much spring pressure adds excessive down force, compacting soil and building excessive soil strength around the seed. Letting the closing wheels "float" on the soil surface without any spring pressure may be adequate to establish soil contact with the seed.
Check behind the planter by digging up a few seeds to evaluate conditions. Using a finger-type or spader wheel might be considered in place of a conventional closing wheel for one or both wheels if they are easily available for use. These types of closing wheels, used by some farmers in wetter soil planting conditions, tend to leave soil looser over the seed.
Hanna adds, "A key point is to recognize existing soil conditions and be willing to make planter adjustments to improve the chances of good early plant growth. In wet soils, inserting the double-disc seed-opener into the ground and establishing seed-to-soil contact typically do not require as much down pressure on depth-gauge wheels and closing wheels, respectively, as is required in drier soils."