The Relation of Nitrogen to Potassium in the Nutrition of Fruit Trees

1. Observations were made on the foliage of a series of Delicious apple trees fertilized with nutrient solutions containing various N/K ratios. When the amount of nitrogen was reduced to one-third of that in the complete-nutrient solution, the development of leaf scorch was retarded and the amount reduced below that of all other cultures receiving additional nitrogen. 2. Increasing the amount of potassium in the complete-nutrient solution was also effective in preventing development of leaf scorch, being just as effective as the reduction of nitrogen. Decreasing the amount of potash or increasing the amount of nitrogen in the nutrient solution was conducive to leaf scorch development. 3. Data on the potassium, nitrogen, and carbohydrate content of the leaves, 1-year wood, and 2-year wood are presented. An attempt was made to correlate the carbohydrate content of the plants with their N/K ratio, but no correlation was found. 4. In general, it may be said that the response of the plants to potassium deficiency seemed to vary with the nitrogen content.