Some corn and soybean fields, mainly in eastern and southern Iowa, are showing potassium (K) deficiency symptoms, even when growth stages range from V3 to V8. The symptom for both crops is yellowing of the leaf margins of the older leaves that usually begins at the leaf tip and extends down the margins toward the leaf base. With severe deficiency the leaf edges may become brown and necrotic, although the newest leaves usually have normal coloration. For further information of symptoms, see Corn leaf potassium deficiency symptoms (ICM 7/1/2002), Is it iron or potassium deficiency? (ICM 7/1/2002), and ISU Extension and Outreach publication Nutrient Deficiencies and Application Injuries in Field Crops (IPM 42).