Abstract
Field and pot experiments were practised during the years 1951 and 1951 in the Aomori Apple Experiment Station to research whether apple leaves absorb urea of foliar fertilization. The principal results obtained in these years summarized as follows.
1. Apple trees were possible to absorb the nitrogen through the leaves from spray solution of urea and the concentration of 5 pound of urea per 100 gallons of water resulted in no burning of leaves, while the concentration of 10 pounds per 100 gallons caused some marginal burning of leaves.
2. Urea sprays increased the leaf color, average nitrogen content (total nitrogen and protein-nitrogen) of the leaves and terminal-growth of apple trees, but did not show significant effects on good fruit color and fruit size.
3. Urea spray recovered the tree vigor of the extremely weakened young Jonathan apple tree which did not form the flower buds for years and consequently about 28 per cent of the treated terminal buds formed blossoms. On the other hand, the flower buds of a plot receiving no urea spray was only 2.9 per cent of the terminal buds.
4. Sprays of urea mixed with lime sulphur and Bordeaux mixture during the end of July to mid August were absorbed through the leaves at the same rate of urea alone and did not burn the leaves by mixing with these chemicals.
