COLUMBUS, Ohio - Unfavorable growing conditions throughout parts of Ohio may be creating emergence problems in corn and soybeans.
Ohio State University Extension agronomists said bouts of heavy rainfall, followed by several days of warm weather, are producing "crusted" soils - a condition whereby the topsoil hardens and seedlings, which are unable to emerge, often "leaf out" underground. The result is either abnormal twisted growth or premature death.
"With normal emergence, a corn plant is usually out of the ground in seven to 10 days. But this year with cool, wet conditions, emergence has been delayed three to four weeks in some cases and crusting has contributed to this delay," said Peter Thomison. "The problem with delayed emergence is that the corn seedling plant uses up its nutrient reserves and is more vulnerable to diseases such as damping off the longer it remains underground." Thomison said the leafing out problem, though somewhere in Ohio every year, is more pervasive this growing season because of the large amounts of rainfall throughout parts of the state have received since mid-May.
"When the soil is tilled really fine, and then you get a hard rain, the soil particles flow back together and harden like concrete," said Jim Beuerlein. "A quarter of an inch to three-quarters of an inch of the soil is real hard. If the soil underneath the crusting is soft, when plants try to emerge, they hit that hard spot and they just end up pushing themselves deeper into the soil." One of the solutions to alleviating "crusting" is to break up the soil with a rotary hoe, weeder, spiketooth harrow or cultipacker, but Thomison urges growers to pay close attention so as not to damage normal-emerging seedlings.
"To minimize poor seedling emergence due to unfurling below the soil surface, watch for cloddy seedbeds, open seed furrows and crusting surface soils after rains. Also check planting depth periodically and adjust accordingly during the planting operation, and monitor herbicide and soil insecticide rates," he said. Certain herbicides and plant hybrids, as well as compaction and light penetration can contribute to underground unfurling of corn plants.
Poor plant performance due to "crusting" isn't the only problem growers have been faced with this growing season.
Heavy localized rainfall and several days of recent freezing temperatures have caused flooding and freeze injury of some plants, enough to warrant either planting additional soybean seeds or replanting certain parts of a cornfield to save the crop.
"There are a million to a million and a half of soybean acres that haven't emerged yet and there is probably going to be some replanting problems due to 'crusting' and freezing injury," said Beuerlein. "Usually what we do is don't destroy what's already there, but just go in and plant more seed. Growers should look at the seeding rate recommendations for the date they want to plant, and if they need to plant 200,000 seeds and already have 50,000 emerged plants, they just need to plant 150,000 more seeds." Thomison said some corn growers in the state might be forced to replant part of their fields, due to problems associated with flood and freeze damage.
"Growers are continuing to diagnose their fields for damage. If the crop was planted before 'ponding' occurred, it may present a problem for corn," said Thomison. "Corn that is growing below the soil surface is very vulnerable to flood damage. The plant uses up all of the oxygen in the soil and the depletion of oxygen results in the plant basically shutting down. The result is a stunted root system and stunted plant growth." Frost damage to corn can create a condition known as "tied whorls," said Thomison. "As new growth occurs and encounters dead tissue, it can result in some abnormal growth. That dead tissue acts as an obstacle and prevents new leaf tissue from emerging. However, usually 90 to 95 percent of the time with favorable growing conditions, the crop will recover." Thomison said growers should assess their crop carefully before deciding to replant.
"With corn that's been possibly damaged, one of the things a grower can do is split the plant lengthwise and take a closer look at the growing point of the plant. If it appears darkened, this probably means it's beginning to rot," he said. "Firm tissue is a good sign the plants are likely to survive." He added that replant decisions should be based on strong evidence that the returns to replanting will not only cover replant costs but also net enough to make it worth the effort. Information like original target plant population/intended plant stand; plant stand after damage; uniformity of plant stand after damage; original planting date; possible replanting date; likely replanting pest control and seed costs should all be considered if replanting is warranted.
"If the stands are uniform and are not reduced significantly based on replant population charts, then the crop may be good enough to keep as is," said Thomison. "The condition of the plants throughout Ohio right now is a mixed bag, and we could see some stand loss associated with both flooding and frost damage." According to the National Agricultural Statistics Service 67 percent of the corn crop has been planted, but localized rainfall has been keeping some farmers out of their fields. Other fields have been replanted due to saturation. Fields in the northern and western regions of the state are seeing the most problems associated with this spring's weather conditions.
"There is a whole gamut of factors conspiring against the plants in these fields," said Thomison. "The condition of some corn plants is not terribly encouraging to growers, and many of them are thinking in terms of either keeping the crop or switching to soybeans. It's a difficult decision for growers right now and we are trying to provide them with some useful guidelines." Beuerlein expects at least a half million acres of corn will be switched over to soybeans. "Some farmers have already given up on corn, while others are still planting the crop," he said. "But I don't expect much corn planting to be going on in June."