The dry conditions this spring have resulted in corn plants expressing potassium (K) deficiency symptoms the past 2 weeks. This phenomenon has appeared in previous dry spring seasons and is back again this year, especially in southern Iowa. Areas of the state that received adequate rainfall are generally not showing K deficiency symptoms. Symptoms can appear even though soil K is adequate for crop production. How can this occur? Uptake of K by plants requires an active root system, especially in the soil zone where plant-available K is located.
Available at: http://works.bepress.com/john-sawyer/151/