By JEFF BURBINK
Extension Educator, Purdue Extension Elkhart County
GOSHEN — Did you notice how fast the corn grew last week? Warm temperature combined with some soil moisture allowed much of the corn crop to grow more than two feet last week!
When corn grows so rapidly, it is not unusual to see potassium (K) leaf deficiency symptoms in fields. Potassium is a mobile nutrient with a plant, and can be transported from older tissue to the areas of faster growth, which causes deficiency symptoms to appear on the older leaves.
On corn, symptoms show as yellowing to necrosis (death) along the edges of older leaves. Symptoms begin at the leaf tip and progress down the edge toward the leaf base.
Potassium deficiency is sometimes confused with nitrogen (N) deficiency symptoms, which also appear on older leaves. N deficiency move down the middle of the leaf tip toward the leaf base.
There are several reasons that K deficiency can occur. The most obvious is when the K levels in the soil have been allowed to drop below maintenance levels in the field. Other causes can be dry soil surface conditions, and localized soil compaction. On younger corn, we sometimes see K deficiency where there was seed furrow side wall compaction and shallow seed planting depth. At other times, root and stalk rot diseases can limit K uptake and cause symptoms as well.
What to do about K deficiency symptoms? Unfortunately there is not a lot you can do about it this season. Foliar feeding of K is typically not practical nor economical, so the key thing to do now is to determine why the symptom is occurring and correct it next year. A simple soil test can determine if the soil levels of K are low and fertilizer needs to be added. If soil tests indicate the levels are fine and that the fertilizer applied this season was more than adequate to meet crop needs, then it’s important to determine if disease or compaction or some other reason can be pinpointed.