It may be too early to think about replanting corn yet, but it's a good time to look at guides from University of Missouri Extension or seed dealers, said MU Extension agronomy specialist Bill Wiebold.
The MU Extension guide "Corn and Soybean Replant Decisions" (G4091) gives a step-by-step procedure for estimating dollar gain or loss from replanting. Producers face tough choices on whether planting date and weather conditions call for replanting. The guide "takes the emotion" out of the decision, Wiebold said.
"It's too early to worry about stands yet," Wiebold said, but the guide helps producers make fact-based decisions when and if the time comes this year.
Seeds that lie in the ground more than 28 days raise concerns about emergence, insects and disease.
Stand density reduces after emergence due to cool weather and disease. The guide gives procedures for measuring sparse stands, and explains that the cost of replanting might exceed the value of the additional yield. Accurate estimates of seed cost, fuel, machinery, labor, pesticide and additional costs should be considered.
The guide gives tables for anticipated yields based on planting dates for both corn and soybean.
Cold water immediately after planting causes low emergence, Wiebold said. Seeds contain 6-8 percent moisture when they go into the ground, then they rehydrate with moisture from the soil. At low temperatures, the hydration process can rupture seed cell membranes. Cell contents can then leak out and become a food source for invading pathogens, leading to death or injury of the seed.
Damage during seed imbibition can knock out 90 percent of the stand. Additionally, emerging seedlings encounter conditions such as crusting. No-till conditions typically have lower soil temperatures and greater soil moisture.
Declines in yield potential due to late planting do not occur much until mid-May, according to Wiebold's four-year study at MU Bradford Research Center.
The guide is available as a free PDF download at www.extension.missouri.edu/p/G4091.