Page:Tree Crops; A Permanent Agriculture (1929).pdf/40

 themselves anew for each harvest. They may, therefore, become victims of the climatic peculiarities of a certain short season. It is rain in July that is so vital to the American corn crop. The rains of June cannot bring a good crop through. Also, if most of the rain due to fall in July happens to come in August, it comes too late. The corn has shot its bolt; it cannot be revived. Trees are much better able than the cereals to use rain when it comes. They can store moisture much better than the annuals can store it because they thrust their roots deep into the earth, seeking moisture far below the surface. They are able to survive drought better than the annual crops that grow beside them. For example, a drought that blasts corn or hay or potatoes may have little influence on the adjacent apple orchard. Trees living from year to year are a permanent institution, a going concern, ready to produce when their producing time comes.

Therefore, the crop-yielding tree offers the best medium for extending agriculture to hills, to steep places, to rocky places, and to the lands where rainfall is deficient. New trees yielding annual crops need to be created for use on these four types of land.

The level plains where rainfall cannot carry soil away may continue to be the empires of the plow, although the development of two-story agriculture (trees above and annual crops below) offers interesting possibilities of a greater yield than can be had from a one-story agriculture.