Effects of potash deficiency and excess on orange trees

Abstract

Abstract does not appear. First page follows. Introduction Many field trials to determine whether citrus would respond to potash have been made in California. No clear-cut indications of the need of potash have come from the tests (Parker and Batchelor, 1942).6 Despite these results, many experienced growers are convinced that potash is indispensable to the maintenance of good quality or production or both, and persist in its use. In an effort to throw further light on the problem, a systematic study was begun by the authors some years ago. Work consisted first in determining the amounts of total, exchangeable, and water-soluble potassium in commercial orchards as compared with the amounts in adjacent nonfertilized areas.7 This survey revealed wide differences in the potash content of citrus orchard soils, suggesting that in some groves potash might be deficient and that in others it might have accumulated to the point of excess. Subsequent efforts were therefore directed toward three objectives : (1) to determine the characteristic effects of potash deficiency and excess on bearing citrus trees; (2) to determine the extent to which fruit quality is influenced by potash variations; and (3) to determine whether the potash content of the leaf or of any other part of the citrus tree is a reliable index of potash deficiency or excess. An exploratory greenhouse experiment with citrus seedlings and cuttings to determine the effects of potash deficiency under a variety of nutrient conditions was carried out (Chapman and Brown, 1942b). This was followed by an outdoor experiment with bearing trees, and it is with this latter experiment that the present paper is concerned.