Warm temperatures: A late winter warmup could cause wheat to come out of dormancy early
March 15, 2016
MANHATTAN, Kan. — The weather over the past several weeks has been uncharacteristically warm for this time of year in Kansas. While many are enjoying being outdoors, this early warm spell has raised concerns for winter wheat across the state.
Romulo Lollato, assistant professor in the Kansas State University Department of Agronomy, said warmer temperatures often lead to accelerated wheat crop development. This could mean that the wheat will break out of dormancy and possibly green up earlier than normal.
In fact, producers in north-central Oklahoma have recently reported certain wheat varieties reaching the first hollow stem stage, said Lollato, a wheat and forages production specialist for K-State Research and Extension. This is something to watch, as it's relatively close to the Kansas border.
The week of Feb. 15-21, temperatures in Kansas averaged 5.1 degrees Fahrenheit warmer than normal. Those high temperatures, coupled with very low humidity, produced an increased drying stress on the crop, according to the Kansas Weather Data Library.
“If we are starting to use the moisture now early in the growing season, we may be hurting our yields later on, in case the spring turns out dry.”
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Lollato said this early warmth bears watching but might not prove detrimental to the wheat crop. There are more factors to consider when predicting the weather's effect on wheat yields, such as how quickly freezing weather returns after a string of warm days and the growing stage the wheat is in when that happens.
"Say that freezing temperatures return (within a few days), most of the wheat may still be in tillering stage or just past tillering," Lollato said. "During this stage, the developing head is still below ground, so it's protected. In that case, most of the damage occurs to the leaf, mainly leaf burning on the leaf tips, so it's mostly cosmetic."
"Now, if these freezing temperatures return in maybe a few weeks and the crop is already at jointing where the developing head is above ground then we do have some temperature thresholds we need to be looking for," he added. "Generally, we say that if temperatures are between 15 and 25 degrees (F) for a long period of time, that developing head can be damaged when wheat is jointing."
Water use concerns
This early breakout of dormancy and early green up could cause the wheat crop to begin using water it had saved for later in the season, now.
"If we are starting to use the moisture now early in the growing season, we may be hurting our yields later on, in case the spring turns out dry," Lollato said. "In case the spring turns out to be of good moisture and good precipitation distribution, this may not be a problem."
The mild late-winter weather may also increase the chances of disease problems in this year's crop carrying over from last year.
"There is the potential for increased overwintering of the disease,"Lollato said. "Producers probably still have fresh in their mind the last growing season where wheat stripe rust was really bad across the state. Often spores of wheat stripe rust will not overwinter as far north as we are here. But with these warm temperatures, if the spores are there and if there's enough moisture, they may overwinter. It's not a bad idea to go out and check for that possibility."
"There have been reports in Texas and Oklahoma of stripe and leaf rust, so it is something that (Kansas) producers need to be aware of," he added. "That's not to say we need to go out and spray, but it is something to be aware of and scout the fields."
Unfortunately, there is not much producers can do to protect against this early green up and breakout of dormancy, because it is a weather issue. Lollato suggests that knowing the status of the crop is the best bet for producers to manage their situation. And remember, warm weather doesn't guarantee a poor yield.
"I think we've had a successful growing season so far, but there is a lot that could still happen at this point," Lollato said. ❖