Already planted corn? Watch soil temps
Though conditions have allowed for some fieldwork and planting in the last few days, the weather window's slamming shut as of mid-week. That's likely to push field conditions back into the cool, damp trend that's been the norm for much of the Corn Belt since early April.
Some farmers have gotten corn into the ground during this recent opening in the weather. If you have, that corn in the ground is likely to face a tough time until warmer, more seasonable temperatures return.
"With the soils being warm and the soils in generally good condition, corn planters are starting to roll," says Iowa State University Extension field agronomist Virgil Schmitt. "However, it looks like soil temperatures may flirt with 50 degrees over the weekend, and corn does not grow at temperatures below 50 degrees."
Soil temperatures were in the low-60s on Tuesday throughout Iowa, for example, but as they fall below the critical 50-degree mark, any corn that's already planted will be susceptible to damage from seed rot, especially with the moisture that's expected to hit the region in the next few days.
"If the germination process has started, it is difficult for the plants to stop the process and then start up again," Schmitt says. "Fields with a history of pythium seedling rots are especially vulnerable to the rots if the soils are both wet and cold."
Though this article deals more with the conditions farmers faced in 2012, ISU Extension agronomist Roger Elmore explains more about the heightened rot and disease risk for corn already in the ground. "With soil temperatures below 50 degrees F., seeds readily absorb water but do not initiate root or shoot growth. This opens up opportunities for insects and pathogens to attack seeds resulting in poor emergence, especially if poor seedbed conditions are prolonged," he says.