As some growers watch the calendar they may realize they are headed into fields that may be less than ideal for planting. Wet soils are easily compacted and sidewall compaction during planting can be a problem, especially if the crop is "mudded-in" and a dry spell occurs after planting.
Most sidewall compaction on wet soils occurs when the press wheels/closing wheels are set with too much down pressure, over packing the seeds into the soil. It is important to plant corn 1.75 – 2 inches deep so that the press wheels are creating good seed-to-soil contact around the seed and not below it where the roots may grow if that seed is planted shallower than 1.5 inches. When properly closing the seed-vee, the sidewalls of the furrow should be fractured as the soil closes around the seed, eliminating the sidewalls and providing good seed-to-soil contact.
A good way to provide loose soil for closing the seed-vee is to do it after the seed is placed in the furrow. Spoked closing wheels are available to replace the standard press wheels. These spoked closing wheels till in the sidewall around the seed. Less aggressive spoked wheels provide some seed-to-soil contact and reduce air pockets around the seed. More aggressive spoked closing wheels tend to dry the soil more. These typically require a seed firmer to provide seed-to-soil contact and a drag chain behind them to level the soil.
Watch Down Pressure
Be careful not to have too much down pressure set on some of these spoked closing wheels as they may “till” the seeds out of the seed-vee. To reduce the aggressiveness of the tillage and to provide some soil firming and depth control, some growers will run one spoked closing wheel and one standard wheel. This situation works well in a wide variety of situations.
While the seed furrow closing devices are important, too much down pressure on the depth gauge wheels will also create sidewall compaction as the disk opens the seed furrow. The disk openers may create some sidewall smearing while pushing the soil outward. If there is too much down pressure on the depth gauge wheels, they will pack the soil downward at the same time, causing compaction that may be too dense for the closing wheels to fracture . When this occurs, growers typically put more pressure on the closing wheels trying to close the seed-vee, making conditions worse yet. Down pressure on both the row unit (gauge wheels) and the closing wheels should be reduced in wet soil conditions.
Use this information as a guide and it should not be the only factor in making decisions.