The soil was a typical arid soil of great depth and had been so cultivated as to contain a large quantity of the natural precipitation. The first five inches of water added to the precipitation already stored in the soil produced forty bushels of wheat. Doubling this amount of irrigation water produced only forty-one bushels of wheat. Even with an irrigation of fifty inches, or ten times that which produced forty bushels, only sixty bushels of wheat, or an increase of one half, were produced. A similar variation may be observed in the case of the other crops. The first lesson to be drawn from this important principle of irrigation is that if the soil be so treated as to contain at planting time the largest proportion of the natural precipitation,—that is, if the ordinary methods of dry-farming be employed,—crops will be produced with a very small amount of irrigation water. Secondly, it follows that it would be a great deal better for the farmer who raises wheat, for instance, to cover ten acres of land with water to a depth of five inches than to cover one acre to a depth of fifty inches, for in the former case four hundred bushels and in the second sixty bushels of wheat would be produced. The farmer who desires to utilize in the most economical manner the small amount of water at his disposal must prepare the land according to dry-farm methods and then must spread the water at his disposal over a larger area of land. The land must be plowed in the fall if the conditions permit, and fallowing should be practiced wherever possible. If the farmer does not wish to fallow his family garden he can achieve equally good results by planting the rows twice as far apart as is ordinarily the case and by bringing the irrigation furrows near the rows of plants. Then, to make the best use of the water, he must carefully cover the irrigation furrow with dry dirt immediately after the water has been applied and keep the whole surface well stirred so that evaporation will be reduced to a minimum. The beginning of irrigation wisdom is always the storage of the natural precipitation. When that is done correctly, it is really remarkable how far a small amount of irrigation water may be made to go.
Under conditions of water scarcity it is often found profitable to carry water to the garden in cement or iron pipes so that no water may be lost by seepage or evaporation during the conveyance of the water from the reservoir to the garden. It is also often desirable to convey water to plants through pipes laid under the ground, perforated at various intervals to allow the water to escape and soak into the soil in the neighborhood of the plant roots. All such refined methods of irrigation should be carefully investigated by the who wants the largest results from his limited water supply. Though such methods may seem cumbersome and expensive at first, yet they will be found, if properly arranged, to be almost automatic in their operation and also very profitable.
Forbes has reported a most interesting experiment dealing with the economical use of a small water supply under the long season and intense water dissipating conditions of Arizona. The source of supply was a well, 90 feet deep. A 3 by 14-inch pump cylinder operated by a 12-foot geared windmill lifted the water into a 5000-gallon storage reservoir standing on a support 18 feet high. The water was conveyed from this reservoir through black iron pipes buried 1 or 2 feet from the trees to be watered. Small holes in the pipe 332 inch in diameter allowed the water to escape at desirable intervals. This irrigation plant was under expert observation for considerable time, and it was found to furnish sufficient water for domestic use for one household, and irrigated in addition 61 olive trees, 2 cottonwoods, 8 pepper trees, 1 date palm, 19 pomegranates, 4 grapevines, 1 fig tree, 9 eucalyptus trees, 1 ash, and 13 miscellancous, making a total of 87 useful trees, mainly fruit-bearing, and 32 vines and bushes. (See Fig. 95.) If such a result can be obtained with a windmill and with water ninety feet below the surface under the arid conditions of Arizona, there should be little difficulty in securing sufficient water over the larger portions of the dry-farm territory to make possible beautiful homesteads.
The dry-farmer should carefully avoid the temptation to decry irrigation practices. Irrigation and dry-farming of necessity must go hand in hand in the development of the great arid regions of the world. Neither can well stand alone in the building of great commonwealths on the deserts of the earth.
CHAPTER XVII
THE HISTORY OF DRY-FARMING
The great nations of antiquity lived and prospered in arid and semiarid countries. In the more or less rainless regions of China, Mesopotamia, Palestine, Egypt, Mexico, and Peru, the greatest cities and the mightiest peoples flourished in ancient days. Of the great civilizations of history only that of Europe has rooted in a humid climate. As Hilgard has suggested, history teaches that a high civilization goes hand in hand with a soil that thirsts for water. To-day, current events point to the arid and semiarid regions as the chief dependence of our modern civilization.
In view of these facts it may be inferred that dry-farming is an ancient practice. It is improbable that intelligent men and women could live in Mesopotamia, for example, for thousands of years without discovering methods whereby the fertile soils could be made to produce crops in a small degree at least without irrigation. True, the low development of implements for soil culture makes it fairly certain that dry-farming in those days was practiced only with infinite labor and patience; and that the great ancient nations found it much easier to construct great irrigation systems which would make crops certain with a minimum of soil tillage, than so thoroughly to till the soil with imperfect implements as to produce certain yields without irrigation. Thus is explained the fact that the historians of antiquity speak at length of the wonderful irrigation systems, but refer to other forms of agriculture in a most casual manner. While the absence of agricultural machinery makes it very doubtful whether dry-farming was practiced extensively in olden days, yet there can be little doubt of the high antiquity of the practice.
Kearney quotes Tunis as an example of the possible extent of dry-farming in early historical days. Tunis is under an average rainfall of about nine inches, and there are no evidences of irrigation having been practiced there, yet at El Djem are the ruins of an amphitheater large enough to accommodate sixty thousand persons, and in an area of one hundred square miles there were fifteen towns and forty-five villages. The country, therefore, must have been densely populated. In the seventh century, according to the Roman records, there were two million five hundred thousand acres of olive trees growing in Tunis and cultivated without irrigation. That these stupendous groves yielded well is indicated by the statement that, under the Caesar's Tunis was taxed three hundred thousand gallons of olive oil annually. The production of oil was so great that from one town it was piped to the nearest shipping port. This historical fact is borne out by the present revival of olive culture in Tunis, mentioned in Chapter XII.
Moreover, many of the primitive peoples of to-day, the Chinese, Hindus, Mexicans, and the American Indians, are cultivating large areas of land by dry-farm methods, often highly perfected, which have been developed generations ago, and have been handed down to the present day. Martin relates that the Tarahumari Indians of northern Chihuahua, who are among the most thriving aboriginal tribes of northern Mexico, till the soil by dry-farm methods and succeed in raising annually large quantities of corn and other crops. A crop failure among them is very uncommon. The early American explorers, especially the Catholic fathers, found occasional tribes in various parts of America cultivating the soil successfully without irrigation. All this points to the high antiquity of agriculture without irrigation in arid and semiarid countries.