WEST LAFAYETTE - One of Indiana’s coldest, snowiest winters in recent history could have damaged some of the state’s winter wheat crop - a fact that necessitates field scouting, a Purdue Extension agronomist says.
While snow cover insulates winter wheat from brutal cold, some parts of the state were hit with sub-zero temperatures when wheat was exposed. In that situation, the crop can suffer a number of injuries that force growers to decide whether to go ahead and apply nitrogen or terminate the crop.
“Whether wheat is at risk depends on where it’s located in the state,” Shaun Casteel said. “The snow blanket protected the crop in some areas, but in others, particularly in the southern part of the state, we didn’t have that snow cover.”
Even though winter wheat enters dormancy for the cold months, temperatures below 12 degrees Fahrenheit sustained for more than two hours can cause freeze injury to exposed wheat. As the crop advances into the jointing growth stage, the temperature point of injury doubles to 24 degrees.
Injury can be as minor as leaf-tip burn or as major as growing-point termination.
In areas that had some soil freezing and thawing cycles, the wheat crop also is at risk for heaving, a phenomenon where water refreezes in soil pores, lifts the soil, pushes the plants up and exposes the roots to drying out.
A third type of winter injury, Casteel said, is smothering. Wheat most at risk is that which is growing in low-lying field areas that ponded when snow melted, then froze again.
“We had a thaw a couple of weeks ago that caused some ponding,” he said. “When ponded water freezes it cuts off the oxygen to the wheat roots underneath. Even though the wheat is dormant, it’s still respiring, so cutting off oxygen can cause plant death.”