'Minor' Elements in Plant Nutrition

Abstract

OUR knowledge of the precise physiological functions of the so-called 'minor' elements in plant nutrition has not kept pace with the growing realization of their importance in agricultural and horticultural practice. A number of papers in the Proceedings of the American Society of Horticultural Science report the effects of certain minor elements on crop growth and behaviour. R. D. Dickey and M. Drossdoff (42, 74; 1943) show that 2 lb. of manganese sulphate per tree applied to the soil cured frenching of the leaves of the tung (Aleurites fordii), due to manganese deficiency. The same authors (42, 79; 1943) describe a 'cupping' of the terminal leaves of the tung, which are reduced in size and show an interveinal chlorosis and sometimes an apical and marginal browning. This may be followed by leaf abscission and shoot die-back; the condition can be cured by applying copper sulphate (1/16 oz. per tree) to the soil. That the disease is due to copper deficiency and the ameliorative effects of the soil dressings of copper sulphate are not due to any indirect effect, is shown by the fact that spraying with copper sulphate is equally effective in curing the disease.