The deficiency symptoms generally begin to appear near midseason and may be first observed when the plants do not “green up” after midseason N applications. As the deficiency progresses, the plants may develop severe disease infestation due to the plants’ reduced ability to resist infection. Diseases that are normally insignificant, such as brown leaf spot and stem rot may become severe in addition to diseases such as rice blast. While these diseases are typically more severe in K-deficient areas, they are not, by themselves, indications of K deficiency. Potassium is highly mobile in the plant, and deficiency symptoms will always occur first and be most severe on the oldest leaves. Older leaves are scavenged for the K needed by younger leaves. Rice leaf tips of the upper leaves often turn yellow and then brown during hot dry periods, however, these symptoms should not be confused with K deficiency.