Cool and wet weather has been the predominant weather pattern the past few weeks, at least in western Iowa. It’s created some extra stress on soybean seedlings. Excess moisture coupled with a recent cold snap can cause damping off, enhance disease infection, and cause chilling injury, which can all lead to reduced soybean stands. If you find yourself with a reduced soybean stand it will be important to weigh your options and evaluate current yield potential, current vs. new planting date, maturity group, and the cost of replanting.

When evaluating soybean stands it is very important to first get an accurate assessment of the current population of viable plants. If soybeans are just starting to emerge, it can be difficult to truly assess what will live. Make sure you give the soybean adequate time to emerge before evaluating. When evaluating viable plants pay close attention to the area below the cotyledons. If a plant is severed or severely damaged in this area it will not live and should not be counted. Be sure to randomly sample several areas throughout the field to get an accurate assessment of the overall stand. When taking stand counts do not just sample the very worst and very best spots. Also, do not avoid areas with gaps in the rows. 

Once you have an assessment of the stand, you need to consider the original planting date, when you would likely be able to replant, and the cost of replanting. University research suggests that plant stands of 73,000 healthy and uniform plants in early June would be worth keeping. Planting soybeans in mid-May and earlier results in 100 percent of yield potential and planting dates of early June and later significantly reduce yields. Early June seeding typically reduces yields to 80-90 percent of full yield potential and continues to go down the later planting is delayed. This is important to consider if replanting cannot occur until early June or later since it will result in reduced yield potential. Lastly, you will need to assess the cost of replanting; time, machinery, and seed are all costs that will need to be considered.

Rarely is a replant question easily answered, but taking the factors discussed above into account will give you the best chance at maximizing your return and yields. For a more in depth look at replant guidelines refer to the Iowa State University “Soybean Replant Decisions” publication (PM 1851). Contact your FS Crop Specialist to discuss replanting needs. 

Originally published in the Iowa Spokesman. Tim Berkland serves the FS System as GROWMARK's strategic agronomy marketing manager. He can be reached at [email protected]