Effect of Differential Nitrogen, Potassium, and Magnesium Supply to Young Valencia Orange Trees in Sand Culture on Mineral Composition Especially of Leaves and Fibrous Roots.

Young, budded Valencia orange trees were grown for several years in outdoor sand cultures with three levels each of nitrogen, potassium, and magnesium in factorial combinations. Total growth and fruitfulness were greatly dependent on the nitrogen level but relatively independent of the two base elements over a very wide range of supply. These responses and those pertaining to fruit quality were recently described in detail (18). The nutritional status of the trees was evaluated by yearly collections of leaf samples. At the termination of the experiment in January, 1951, samples of leaves, fibrous roots, and woody structures were taken. The present report describes some of the results of mineral analyses made on these tissues. About 5,000 individual determinations of elements were made on over 900 samples. Only mean values are presented in the tables, for illustrative purposes. They represent the main trends and relations found.