Potassium deficient corn caused by extremely dry soil in South Dakota

Farm Forum

BROOKINGS, S.D. – Very dry soil conditions in the northeast have caused soil potassium (K) to become unavailable to crops, especially corn, however Anthony Bly, SDSU Extension Soils Field Specialist said application of potassium fertilizers at this point are not recommended.

“The very dry soil will not allow the plants to take up the nutrient,” Bly said. “It’s the extreme soil drying which has temporarily trapped potassium (K) between the clay layers in the soil.”

Bly explained that when the soil dries, the clay layers shrink and collapse around the potassium (K).

“Cracks in the soil are indicative of clay shrinkage and as soon as precipitation is received the soil will swell and the potassium will become plant available,” he said.

Corn plant potassium (K) deficiency symptoms, Bly said, occur on the lower plant leaves at onset and move up the plant as the deficiency worsens. Plant leaves show a yellowing and necrosis (dead tissue) along the leaf margins (edges) with worse symptoms at the leaf tip.

“This should not be confused with nitrogen deficiency as it also occurs on the lower leaves of the plant at onset but does not occur along the leaf edges, instead nitrogen deficiency starts at the leaf tip and moves in a V-pattern down the leaf mid-rib,” Bly said.

Soil test comparisons before and after the extreme soil drying show huge changes in plant available potassium (K) as shown in the following table.