Exercise patience in deciding when to commence field operations

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

The recent extended period of rainy weather has growers anxious to get on the tractor and resume planting and in some cases, begin planting corn. The extreme wet weather in late April that affected most of the state has delayed corn planting relative to past years. Fortunately, modern planting equipment allows for rapid planting once fields finally dry out. I heard a grower remark once that with current modern farm machinery, “the entire state of Michigan can be planted in about a week’s time.”

The operative word is patience when deciding when to restart field operations. The potential yield loss from planting in fields that are too wet far outweighs the potential yield loss from delaying planting until field conditions are suitable. Planting in wet conditions often results in sidewall compaction of the seed furrow. This causes poor seed to soil contact which has several negative consequences including: reduced germination and poor stands; uneven emergence which reduces yield due to plant-to-plant competition; and, restricted root growth which compromises the plant’s ability to withstand moisture stress which we often experience later in the growing season.

In addition, the limited rooting can result in phosphorus deficiency even though soil test phosphorus levels are adequate. This occurs because the plant uses all of the phosphorus that is immediately available within the seed furrow. The roots of these plants will appear thickened and gnarled a visual sign of compaction. After a period of time, roots may break through compacted seed furrow sidewalls and into the soil profile. As this occurs initial phosphorus deficiency may be overcome and the plant will begin growing normally again. However, sidewall smearing and compaction will likely set the crop back by a week or more as it struggles to overcome the less than optimum soil environment.

Corn hybrids have a limited ability to advance through growth stages faster when planted later than their optimum planting date. Research at MSU has shown that late-planted corn will progress through vegetative and reproductive development stages slightly faster relative to the same hybrid when planted earlier. However, this assumes that the hybrid’s relative maturity is acceptable for your maturity zone. The MSU Weather Office has a website featuring local data that can be accessed to determine average growing degree day (GDD) accumulations for your part of the state. Or check the options at Enviro-weather’s web site. Work with your seed dealer to determine which hybrids can reasonably be expected to mature in your area.

Research has shown that under average Michigan conditions, it generally pays to switch to a short season hybrid in late May. The basis for the cost effectiveness of switching to a short season hybrid is primarily in the ability to harvest dryer grain in the fall. The optimum time to pull the trigger on the switch to a short season hybrid will vary from year to year depending on weather conditions, but it is generally around the third to fourth week of May for much of Michigan. The website referenced above can be used to determine the average remaining GDD’s left in the growing season when determining what the relative maturity of your short season hybrid should be.

In summary, do not resume planting if soil conditions are too wet. There is still adequate time in the growing season to establish a good crop.

Figure 1. Effect of date of planting on GDD to emergence, silking, and blacklayer formation.Effect of date of planting on GDD to emergence, silking, and blacklayer formation.

Graph key
DOP = date of planting, 1 = earliest date (mid-April), 5 = latest date (early June)
Bars having the same letter are not significantly different at P = 0.05.
The missing light-colored bars indicate that corn did not mature to blacklayer for
that planting date. Bar graph sections with a different letter represent GDD
accumulations that are statistically different at P > 0.05.

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