As rain delayed corn and soybean planting in various areas of Iowa this May, two of the often-asked questions have been: Is it wise to go into a wet field with a field cultivator and use it to try to stir the soil in an effort to get soil to dry faster? Also, it's May 17--should I forget about planting the normal maturity corn for my area and switch to an earlier maturing hybrid?
When weather conditions of frequent rain cause saturated conditions in soils, agronomists caution farmers to not work soils too wet. But what about hitting a field with some light tillage, just to try to stir the soil and make it dry out faster so you can get in and get it planted?
"With regard to using some sort of light tillage operations, such as a field cultivator, to try to dry out wet soil, chances are you'll end up doing more harm than good," says Mahdi Al-Kaisi, Iowa State University Extension soil management specialist at Ames. "Tilling soil in order to dry the soil surface or control weeds will probably have significant negative impacts on creating proper seedbed conditions, and it will likely increase soil compaction."
Don't waste time, fuel on unnecessary tillage
When early weeds have emerged but surface soil is still too wet for no-till planting, growers often consider doing shallow field cultivation in an attempt to kill winter annual weeds. The non-no-till farmers sometimes consider field cultivating or disking simply to dry the soil. Before spending time and fuel for cultivation, you need to analyze the potential effects on weeds and soil, cautions Al-Kaisi.
"When tilled wet, many soils slab into large blocks, keeping the root system of growing weeds intact and allowing them to continue growth," he says. "Larger clods on the soil surface may require a secondary tillage pass before the soil is acceptable for planter operation. So you end up not getting the weed control you wanted and you create a cloddy seedbed for the planter."
Pre-plant tillage passes on wet soil also add random wheel tracks and produce a greater likelihood that some seedling roots will need to penetrate compacted soil, adds Al-Kaisi. These less desirable soil conditions for early seedling development caused by tillage may negate the perceived advantage of earlier planting. Further discussion on compaction that is created when working soils wet can be found in an earlier ISU Extension article "How soon should I start field operations?"
When is it time to switch corn maturities?
As planting is delayed by wet soils beyond May 15, farmers are getting anxious and are wondering whether they should switch to an earlier maturing corn hybrid?
"Adapted full season corn hybrids for your location can compensate somewhat for later planting such that we don't recommend switching to an earlier maturing corn hybrid until about May 25," says Brian Lang, ISU Extension field agronomist in northeast Iowa. However, if you purchased "extended full season" corn hybrids that you routinely planted in past years in late April, and counted on good fall weather, and those hybrids aren't planted yet, then it is now time to move to an adapted full-season hybrid, he adds.