Effect of the Time of Application of Fertilizer Nitrogen on the Growth, Flowering and Fruiting of Maiden Apple Trees Grown in Sand Culture

Abstract

Mailing II rootstocks were grown throughout 1960 in sand on nutrient culture solutions containing 1, 4 or 10 mg. equivalents of nitrogen as nitrate (referred to as N₄, N₁₀ rootstocks) and during that summer each rootstock was budded with the variety Lord Lamboume. The growth, flowering and fruiting performance of the resultant maiden shoots were recorded from bud break 1961 to fruit set 1962. Throughout this second period each tree was given only a minimum of nitrogen (N_x) except during a certain period of one or two months’ duration, when it received a simulated fertilizer application (N₁₀). The greatest amount of primary extension growth in 1961 took place on the maidens given supplementary nitrogen in June on the N₁ and N₄ rootstocks and in July on the N₁₀. Secondary extension growth in 1961 was apparently induced by supplementary nitrogen given to the maidens on the N4 stocks in July and to those on the N_x in August. The highest number of fruit buds and blossoms in 1962 resulted from the June 1961 high-nitrogen supplement to the maidens on the N_r and N₄ stocks and from the July supplement to the N₁₀. After open pollination, the maidens grown on the NIO stocks set fruit better than on those that were more nitrogen-deficient. Among the N₁₀ and N₊ maidens, those receiving the September nitrogen supplement gave the highest yield. These results are discussed especially in relation to apparent differences in quantity and quality of blossoms. It is suggested that the quantity of blossoms is related to the amount of primary extension growth, while the quality is determined by the extent to which reserves of carbohydrate and nitrogen have been accumulated during the previous autumn.