Crop injury from waterlogging and ice sheeting are primarily caused by the lack of oxygen to the growing point of wheat according to Jill Scheidt, agronomy specialist with University of Missouri Extension.
Research and observations suggest most crop plants submerged for more than five to seven days, when temperatures are greater than 65 degrees, will die and yield can be impacted by flooding in as few as 48 hours.
“Under cooler temperatures, the negative effects of flooding take longer to impact plant tissues, so winter wheat should tolerate flooding better than midsummer conditions,” said Scheidt.
Dormancy greatly reduces the requirement for oxygen but does not eliminate it.
“With a warm December, the winter crops were not dormant when the wet weather began, so some stand loss is expected in fields saturated for long periods,” said Scheidt.
Before green-up, or at the beginning of erect growth, Scheidt recommends bringing a sample inside a warm building and observe it for regrowth after a couple of days. If the plant is in good condition, new leaf growth and white roots appear, and the crown will appear white and healthy.
“To determine if there is a need to replant, count plants at green-up. The critical threshold for a wheat grain field is an average of 12 to 15 live plants per square foot,” said Scheidt.
Excessive water can cause denitrification and leaching of nitrate nitrogen. Soil temperatures below 50 degrees Fahrenheit slow these processes, so the loss of nitrogen may not be significant.
“The majority of nitrogen fertilizer should be applied before jointing to maximize the yield response in winter wheat,” said Scheidt.