Extension field specialists have reported that potassium (K) deficiency symptoms are beginning to be observed on corn in east central Iowa. These symptoms are yellowing of the leaf margins of the older (bottom) leaves. The yellowing begins at the leaf tip and extends down the margins toward the stalk. In most cases, a soil test shows adequate to high levels of K. These symptoms can occur after a prolonged dry spell and usually are observed first in ridge-tillage systems and then no-till. If the dry conditions last long enough, we will see it in all tillage systems.
K deficiency symptoms develop because plants cannot extract K from the dry surface soil. This is compounded in soils that have very low subsoil K, like many soils in east central Iowa. If we get into a more normal rainfall pattern the plants will recover with little or no loss of yield.
This article originally appeared on page 117 of the IC-478(15) -- June 30, 1997 issue.