University of Illinois crop specialist Fabian Fernandez says dry conditions across the Midwest are causing a multitude of nutrient deficiency problems. However, he says neither foliar or soil application of nutrients will solve the problem -- only rain will help.
"Many cornfields show potassium deficiency even though adequate fertility is present in the soil... One question being asked is why deficiency of potassium is showing up in corn more than deficiency of any other nutrient," says Fernandez.
Fernandez says there could be several reasons, "but I believe the most likely one is that, unlike with nitrogen and phosphorus, large amounts of potassium are taken up rapidly by corn early in development." He explains, "Soon after the V12 development stage, corn has already taken up half of all the potassium it will need, and by the R1-R2 development stages, it has taken up all it will need (around 170 lb of K2O/acre). This is in contrast with nitrogen and phosphorus, which continue to be taken up until sometime after the dent stage (R5). Also, unlike nitrogen, which moves freely over large distances in the soil solution, phosphorous and potassium can only move at most a few short millimeters in the soil solution, which causes these nutrients to become positionally unavailable to the crop when the soil dries out."
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"I recommend for the future that you minimize the effect of drought by ensuring that whatever water is present in the soil is protected to be used by the crop," says Fernancez. "Some farmers have seen firsthand this year how much water weeds can take up when not treated early in the season. Similarly, too much tillage has in some situations caused unnecessary water evaporation from the soil, and those fields are running out of water sooner than fields that were managed more carefully."