Time to topdress droughty wheat?
They called it “The Blizzard of Oz” -- the storm that dumped as much as 19 inches of heavy, wet snow in late February across the windy and bone-dry region of the central and southern Plains.
Winter-wheat farmers throughout Kansas and the surrounding region took it as a sign that the worst drought in history might finally have broken - and that the struggling wheat crop might be turning a corner.
While farmers unfortunately still had to contend with the parched subsoil below, the heavy blanket of snow still sparked thoughts of how to pencil in a top-dressed fertilizer application in the spring.
“I can speak for myself in that every time it snows I get excited,” says David Mengel, soil fertility and nutrient management expert at Kansas State University. “When you get a little bit of moisture, the wheat can survive another week or two. But it’s still really dry down below.”
The dry soil profile below has left farmers sitting tight and wondering how to plan their next move, Mengel says. But they may not have to worry. Farmers might find another treasure deep in the soil: residual nitrogen the previous crop failed to use during last year’s excruciating drought.
“How much nitrogen was present in the soil to begin with is going to be a critical factor in deciding to topdress. And that’s going to be a function of what they planted into in terms of crop residue, fallow and whatever that may be,” explains Mengel.
Soil samples sent in to Kansas State University’s agronomy lab show there generally is a significant amount of nitrogen present following failed corn or grain sorghum crops, he adds.
Researchers at the University of Nebraska-Lincoln also report that soil samples there have indicated unusually high residual soil nitrate levels, citing less nitrogen uptake where yields were low, dry conditions that caused reduced leaching and less denitrification, and an increased decomposition rate of crop residue as the reasons for high soil nitrate levels.
That residual nitrogen leftover from the previous crop, Mengel says, is a good thing for the struggling wheat crop that might have followed.
“It gives you a little more time to sort of ride this out and see what the yield potential is actually going be, whether we get the spring rain or not,” he says.
Stopping N Deficiency
However, farmers may be dealing with the opposite scenario if they held back on their fertility program last fall amidst concern of continued drought and of the wheat crop not being able to utilize what was put in the soil.
In that case, Mengel says, the wheat crop – having already been stressed by drought – may be stressed further by nitrogen deficiency.
“If we get some moisture and the crop really starts to go, it’ll rapidly use up a lot of nitrogen,” he says. “At this point, the last thing you want to do is put some nitrogen stress on it. That’s going to limit the number of tillers or cause the abortion of some tillers that are out there.”