Page:Tree Crops; A Permanent Agriculture (1929).pdf/351

 one mile of inside fences. Crop-yielding trees along these fences will not interfere with the machine agriculture in any way. Of course the trees should not be there if they cannot pay with their own crops for the reduction of crops they make in the field. In a recent journey from New York to St. Louis, and thence to San Antonio, Texas, I was struck by the great number of fruitless trees standing in the midst of fields that were prime for machinery.

Tens of thousands of farms have an uncultivated corner across the gully, beside a stream bank, or a chopped-out bit of woods. In all these places trees will grow. If the land is not pastured too hard, the seeds of walnuts and hickories and many others will grow up ready to be grafted in a few years by him who would experiment.

"Oasis agriculture in the Sahara, Arabia, and other tropical desert regions is made possible, principally, by date palms, which act as windbreaks and as shade for tender plants beneath, while drawing the wherewithal for a valuable fruit crop from the basement stories of the soil.

Several hundred thousand square miles of the middle western United States are so level that the wind fairly combs the grass because there are no hills or forests to prevent or disturb its close approach to the earth.

In this region the farmers have planted windbreaks about their houses and farm buildings and now the agricultural scientist has found the windbreak is a needed protection to the grain field.

"Measurements made in fields of small grain indicate that the crop gain in the protected zone is sufficient to offset fully the effects of shading and sapping. In a wheat field protected by a dense windbreak the gain amounted to about ten bushels per acre where the protection was most complete, and grad-