Page:Tree Crops; A Permanent Agriculture (1929).pdf/334

 a little apple tree and kill it, whereas three feet of mulch plus nitrate of soda will cause it to grow like the green bay tree of Scripture and bear more apples, alas, than I can sell. Experimenters growing nut trees and other crop trees can plant them in almost any kind of place if they will give the trecs a smothering coat of grass mulch three or four feet from the trunk, and in addition give fertilizer and other attention that a cultivated tree should have. Guaranteed this treatment, most species will react as the apple does. When the top is large enough to shade the ground around the trunk, the trees can usually fight it out and make steady growth if abundantly fertilized. This statement is made for the naturally forested areas of the eastern United States. I do not know how far west it holds true. It is probably not true for the Great Plains.

Legumes of grass size, bush size, or tree size can sometimes be made grow beside the crop-yielding non-leguminous tree and fertilize it with nitrogen (page 65). These possibilities have been as yet but little explored in the temperate zones.

Fig. 23 shows a method of making a pocket in the earth so that the water will remain upon the square rod where it falls. The effect of this is like that of cultivation or fertilizer because it increases available moisture and increases the available food supply of the plant. Irrigation by water pockets should be one of the devices of the agriculture of the future, particularly the tree agriculture. Once the pit is made the rains will automatically fill it, and the tree will irrigate itself for years with very little attention save an occasional cleaning out of the pit or ditch or terrace. Otherwise the forces of nature would gradually tend to level the pockets.