Effects of potash deficiency and excess on orange trees

To the authors' knowledge no one has grown bearing citrus trees in controlled nutrient media of variable potassium supply over a long enough period to determine the effects of both potash deficiency and excess on the growth, foliage, composition, and fruit quality. Reed and Haas (1923) grew young orange trees in sand culture without potassium (sodium was substituted for potassium) for 17 months. Only the very earliest stages of potassium deficiency developed during this period. In describing these early symptoms, the authors state that some of the leaves produced were undersized and that the chlorophyll in some was faded. These effects were more pronounced on the south side of the tree. Some iron chlorosis was also seen. Haas (1936) later grew young citrus trees in sand cultures lacking potassium. He noted some scorching of leaves, twig dieback, and gum exudation on the wood. Some of the leaves showed resinous spots. No fruit was produced on these trees. Bryan (1935) grew grapefruit seedlings in potassium-deficient cultures and noted first a stimulation of growth, followed later by retardation. There was leaf puckering, and the fading of chlorophyll in small irregular spots on the leaf. Bryan also noted pustularlike brown spots on the leaves. The branches drooped and showed a lack of rigidity. They also indicate that fruit from trees minus this element has thick, rough rind, and that its keeping quality is impaired.