The Apple by William H. Barnes and Kansas State Horticultural Society

In the cultivation of the apple tree, which, like most plants, gets its nourishment from two sources, the soil and the atmosphere, these must be first considered. From the soil come the mineral ingredients, those that are given back to the soil when the plant is burned, and from the atmosphere come the ingredients of no less importance in the growth of the tree, but which mostly disappear as invisible gases upon combustion. Upon the character of this soil, and upon the climate, a general term that may be said to cover the conditions of the atmosphere, depend the success of the horticulturist. In addition to this, insect pests are liable to constantly menace the crop.