IRRIGATION AND DRY-FARMING
IRRIGATION-farming and dry-farming are both systemsof agriculture devised for the reclamation of countries that ordinarily receive anannual rainfall of twenty inches or less. Irrigation-farming cannot of itself reclaimthe arid regions of the world, for the available water supply of arid countries whenit shall have been conserved in the best possible way cannot be made to irrigatemore than one fifth of the thirsty land. This means that under the highest possibledevelopment of irrigation, at least in the United States, there will be five or sixacres of unirrigated or dry-farm land for every acre of irrigated land. Irrigationdevelopment cannot possibly, therefore, render the dry-farm movement valueless. Onthe other hand, dry-farming is furthered by the development of irrigation farming,for both these systems of agriculture are characterized by advantages that make irrigationand dry-farming supplementary to each other in the successful development of anyarid region.
Under irrigation, smaller areas need to be cultivatedfor the same crop returns, for it has been amply demonstrated that the acre yieldsunder proper irrigation are very much larger than the best yields under the mostcareful system of dry-farming. Secondly, a greater variety of crops may be grownon the irrigated farm than on the dry-farm. As has already been shown in this volume,only certain drouth resistant crops can be grown profitably upon dry-farms, and thesemust be grown under the methods of extensive farming. The longer growing crops, includingtrees, succulent vegetables, and a variety of small fruits, have not as yet beenmade to yield profitably under arid conditions without the artificial applicationof water. Further, the irrigation-farmer is not largely dependent upon the weatherand, therefore, carries on this work with a feeling of greater security. Of course,it is true that the dry years affect the flow of water in the canals and that thefrequent breaking of dams and canal walls leaves the farmer helpless in the faceof the blistering heat. Yet, all in all, a greater feeling of security is possessedby the irrigation farmer than by the dry-farmer.
Most important, however, are the temperamentaldifferences in men which make some desirous of giving themselves to the cultivationof a small area of irrigated land under intensive conditions and others to dry-farmingunder extensive conditions. In fact, it is being observed in the arid region thatmen, because of their temperamental differences, are gradually separating into thetwo classes of irrigation-farmers and dry-farmers. The dry-farms of necessity covermuch larger areas than the irrigated farms. The land is cheaper and the crops aresmaller. The methods to be applied are those of extensive farming. The profits onthe investment also appear to be somewhat larger. The very necessity of pitting intellectagainst the fierceness of the drouth appears to have attracted many- men to the dry-farms.Gradually the certainty of producing crops on dry-farms from season to season isbecoming established, and the essential difference between the two kinds of farmingin the arid districts will then he the difference between intensive and extensivemethods of culture. Men will be attracted to one or other of these systems of agricultureaccording to their personal inclinations.
The scarcity of water
For the development of a well-rounded commonwealthin an arid region it is, of course) indispensable that irrigation be practiced, fordry-farming of itself will find it difficult to build up populous cities and to supplythe great variety of crops demanded by the modern family. In fact, one of the greatproblems before those engaged in the development of dry-farming at present is thedevelopment of homesteads in the dry-farms. A homestead is possible only where thereis a sufficient amount of free water available for household and stock purposes.In the portion of the dry-farm territory where the rainfall approximates twenty inches,this problem is not so very difficult, since ground water may be reached easily.In the drier portions, however, where the rainfall is between ten and fifteen inches,the problem is much more important. The conditions that bring the district underthe dry-farm designation imply a scarcity of water. On few dry-farms is water availablefor the needs of the household and the barns. In the Rocky Mountain states numerousdry-farms have been developed from seven to fifteen miles from the nearest sourceof water, and the main expense of developing these farms has been the hauling ofwater to the farms to supply the needs of the men and beasts at work on them. Naturally,it is impossible to establish homesteads on the dry-farms unless at least a smallsupply of water is available; and dry-farming will never he what it might be unlesshappy homes can be established upon the farms in the arid regions that grow cropswithout irrigation. To make a dry-farm homestead possible enough water must be available,first of all, to supply the culinary needs of the household. This of itself is notlarge and, as will be shown hereafter, may in most cases be obtained. However, inorder that the family may possess proper comforts, there should be around the homesteadtrees, and shrubs, and grasses, and the family garden. To secure these things a certainamount of irrigation water is required. It may be added that dry-farms on which suchhomesteads are found as a result of the existence of a small supply of irrigationwater are much more valuable, in case of sale, than equally good farms without thepossibility of maintaining homesteads. Moreover, the distinct value of irrigationin producing a large acre yield makes it desirable for the farmer to use all thewater at his disposal for irrigation purposes. No available water should be allowedto flow away unused.
Available surface water
The sources of water for dry-farms fall readilyinto classes: surface waters and subterranean waters. The surface waters, whereverthey may be obtained, are generally the most profitable. The simplest method of obtainingwater in an irrigated region is from some irrigation canal. In certain districtsof the intermountain region where the dry farms lie above the irrigation canals andthe irrigated lands below, it is comparatively easy for the farmers to secure a smallbut sufficient amount of water from the canal by the use of some pumping device thatwill force the water through the pipes to the homestead. The dry-farm area that maybe so supplied by irrigation canals is, however, very limited and is not to be consideredseriously in connection with the problem.
A much more important method, especially in themountainous districts, is the utilization of the springs that occur in great numbersover the whole dry-farm territory. Sometimes these springs are very small indeed,and often, after development by tunneling into the side of the hill, yield only atrifling flow. Yet, when this water is piped to the homestead and allowed to accumulatein small reservoirs or cisterns, it may be amply sufficient for the needs of thefamily and the live stock, besides having a surplus for the maintenance of the lawn,the shade trees, and the family garden. Many dry-farmers in the intermountain countryhave piped water seven or eight miles from small springs that were considered practicallyworthless and thereby have formed the foundations for small village communities.
Of perhaps equal importance with the utilizationof the naturally occurring springs is the proper conservation of the flood waters.As has been stated before, arid conditions allow a very large loss of the naturalprecipitation as run-off. The numerous gullies that characterize so many parts ofthe dry-farm territory are evidences of the number and vigor of the flood waters.The construction of small reservoirs in proper places for the purpose of catchingthe flood waters will usually enable the farmer to supply himself with all the waterneeded for the homestead. Such reservoirs may already be found in great numbers scatteredover the whole western America. As dry-farming increases their numbers will alsoincrease.
When neither canals, nor springs, nor flood watersare available for the supply of water, it is yet possible to obtain a limited supplyby so arranging the roof gutters on the farm buildings that all the water that fallson the roofs is conducted through the spouts into carefully protected cisterns orreservoirs. A house thirty by thirty feet, the roof of which is so constructed thatall that water that falls upon it is carried into a cistern will yield annually undera a rainfall of fifteen inches a maximum amount of water equivalent to about 8800gallons. Allowing for the unavoidable waste due to evaporation, this will yield enoughto supply a household and some live stock with the necessary water. In extreme casesthis has been found to be a very satisfactory practice, though it is the one to beresorted to only in case no other method is available.
It is indispensable that some reservoir be providedto hold the surface water that may be obtained until the time it may be needed. Thewater coming constantly from a spring in summer should be applied to crops only atcertain definite seasons of the year. The flood waters usually come at a time whenplant growth is not active and irrigation is not needed.
The rainfall also in many districts comes mostlargely at seasons of no or little plant growth. Reservoirs must, therefore, be providedfor the storing of the water until the periods when it is demanded by crops. Cement-linedcisterns are quite common, and in many places cement reservoirs have been found profitable.In other places the occurrence of impervious clay has made possible the establishmentand construction of cheap reservoirs. The skillful and permanent construction ofreservoirs is a very important subject. Reservoir building should be undertaken onlyafter a careful study of the prevailing conditions and under the advice of the stateor government officials having such work in charge. In general, the first cost ofsmall reservoirs is usually somewhat high, but in view of their permanent serviceand the value of the water to the dry-farm they pay a very handsome interest on theinvestment. It is always a mistake for the dry-farmer to postpone the constructionof a reservoir for the storing of the small quantities of water that he may possess,in order to save a little money. Perhaps the greatest objection to the use of thereservoirs is not their relatively high cost, but the fact that since they are usuallysmall and the water shallow, too large a proportion of the water, even under favorableconditions, is lost by evaporation. It is ordinarily assumed that one half of thewater stored in small reservoirs throughout the year is lost by direct evaporation.
Available subterranean water
Where surface waters are not readily available,the subterranean water is of first importance. It is generally known that, underlyingthe earth's surface at various depths, there is a large quantity of free water. Thoseliving in humid climates often overestimate the amount of water so held in the earth'scrust, and it is probably true that those living in arid regions underestimate thequantity of water so found. The fact of the matter seems to be that free water isfound everywhere under the earth's surface. Those familiar with the arid West havefrequently been surprised by the frequency with which water has been found at comparativelyshallow depths in the most desert locations. Various estimates have been made asto the quantity of underlying water. The latest calculation and perhaps the mostreliable is that made by Fuller, who, after a careful analysis of the factors involved,concludes that the total free water held in the earth's crust is equivalent to auniform sheet of water over the entire surface of the earth ninety-six feet in depth.A quantity of water thus held would be equivalent to about one hundredth part ofthe whole volume of the ocean. Even though the thickness of the water sheet underarid soils is only half this figure there is an amount, if it could be reached, thatwould make possible the establishment of homesteads over the whole dry-farm territory.One of the main efforts of the day is the determination of the occurrence of thesubterranean waters in the dry-farm territory.
Ordinary dug wells frequently reach water atcomparatively shallow depths. Over the cultivated Utah deserts water is often foundat a depth of twenty-five or thirty feet, though many wells dug to a depth of onehundred and seventy-five and two hundred feet have failed to reach water. It maybe remarked in this connection that even where the distance to the water is small,the piped well has been found to be superior to the dug well. Usually, water is obtainedin the dry-farm territory by driving pipes to comparatively great depths, rangingfrom one hundred feet to over one thousand feet. At such depths water is nearly alwaysfound. Often the geological conditions are such as to force the water up above thesurface as artesian wells, though more often the pressure is simply sufficient tobring the water within easy pumping distance of the surface. In connection with thissubject it must be said that many of the subterranean waters of the dry-farm territoryare of a saline character. The amount of substances held in solution varies largely,but frequently is far above the limits of safety for the use of man or beast or plants.The dry-farmer who secures a well of this type should, therefore, be careful to havea proper examination made of the constituents of the water before ordinary use ismade of it.
Now, as has been said, the utilization of thesubterranean waters of the land is one of the living problems of dry-farming. Thetracing out of this layer of water is very difficult to accomplish and cannot bedone by individuals. It is a work that properly belongs to the state and nationalgovernment. The state of Utah, which was the pioneer in appropriating money for dry-farmexperiments, also led the way in appropriating money for the securing of water forthe dry-farms from subterranean sources. The world has been progressing in Utah since1905, and water has been secured in the most unpromising localities. The most remarkableinstance is perhaps the finding of water at a depth of about five hundred and fiftyfeet in the unusually dry Dog Valley located some fifteen miles west of Nephi.
The use of small quantities of water on the dry-farmscarries with it, in most cases, the use of small pumping plants to store and to distributethe water properly. Especially, whenever subterranean sources of water are used andthe water pressure is not sufficient to throw the water above the ground, pumpingmust be resorted to. The pumping of water for agricultural purposes is not at allnew. According to Fortier, two hundred thousand acres of land are irrigated withwater pumped from driven wells in the state of California alone. Seven hundred andfifty thousand acres are irrigated by pumping in the United States, and Mead statesthat there are thirteen million acres of land in India which are irrigated by waterpumped from subterranean sources. The dry-farmer has a choice among several sourcesof power for the operation of his pumping plant. In localities where winds are frequentand of sufficient strength windmills furnish cheap and effective power, especiallywhere the lift is not very great. The gasoline engine is in a state of considerableperfection and may be used economically where the price of gasoline is reasonable.Engines using crude oil may be most desirable in the localities where oil wells havebeen found. As the manufacture of alcohol from the waste products of the farms becomesestablished, the alcohol-burning engine could become a very important one. Over nearlythe whole of the dry-farm territory coal is found in large quantities, and the steamengine fed by coal is an important factor in the pumping of water for irrigationpurposes. Further, in the mountainous part of the dry-farm territory water Poweris very abundant. Only the smallest fraction of it has as yet been harnessed forthe generation of the electric current. As electric generation increases, it shouldbe comparatively easy for the farmer to secure sufficient electric power to run thepump. This has already become an established practice in districts where electricpower is available.
During the last few years considerable work hasbeen done to determine the feasibility of raising water for irrigation by pumping.Fortier reports that successful results have been obtained in Colorado, Wyoming,and Montana. He declares that a good type of windmill located in a district wherethe average wind movement is ten miles per hour can lift enough water twenty feetto irrigate five acres of land. Wherever the water is near the surface this shouldbe easy of accomplishment. Vernon, Lovett, and Scott, who worked under New Mexicoconditions, have reported that crops can be produced profitably by the use of waterraised to the surface for irrigation. Fleming and Stoneking, who conducted very carefulexperiments on the subject in New Mexico, found that the cost of raising throughone foot a quantity of water corresponding to a depth of one foot over one acre ofland varied from a cent and an eighth to nearly twenty-nine cents, with an averageof a little more than ten cents. This means that the cost of raising enough waterto cover one acre to a depth of one foot through a distance of forty feet would average$4.36. This includes not only the cost of the fuel and supervision of the pump butthe actual deterioration of the plant. Smith investigated the same problem underArizona conditions and found that it cost approximately seventeen cents to raiseone acre foot of water to a height of one foot. A very elaborate investigation ofthis nature was conducted in California by Le Conte and Tait. They studied a largenumber of pumping plants in actual operation under California conditions, and determinedthat the total cost of raising one acre foot of water one foot was, for gasolinepower, four cents and upward;. for electric power, seven to sixteen cents, and forsteam, four cents and upward. Mead has reported observations on seventy-two windmillsnear Garden City, Kansas, which irrigated from one fourth to seven acres each ata cost of seventy-five cents to $6 per acre. All in all, these results justify thebelief that water may be raised profitably by pumping for the purpose of irrigatingcrops. When the very great value of a little water on a dry-farm is considered, thefigures here given do not seem at all excessive. It must be remarked again that areservoir of some sort is practically indispensable in connection with a pumpingplant if the irrigation water is to be used in the best way.
The use of small quantities of water in irrigation
Now, it is undoubtedly true that the acre costof water on dry-farms, where pumping plants or similar devices must be used withexpensive reservoirs, is much higher than when water is obtained from gravity canals.It is, therefore, important that the costly water so obtained be used in the mosteconomical manner. This is doubly important in view of the fact that the water supplyobtained on dry-farms is always small and insufficient for all that the farmer wouldlike to do. Indeed, the profit in storing and pumping water rests largely upon theeconomical application of water to crops. This necessitates the statement of oneof the first principles of scientific irrigation practices, namely, that the yieldof a crop under irrigation is not proportional to the amount of water applied inthe form of irrigation water. In other words, the water stored in the soil by thenatural precipitation and the water that falls during the spring and summer can eithermature a small crop or bring a crop near maturity. A small amount of water addedin the form of irrigation water at the right time will usually complete the workand produce a well-matured crop of large yield. Irrigation should only be supplementedto the natural precipitation. As more irrigation water is added, the increase inyield becomes smaller in proportion to the amount of water employed. This is clearlyshown by the following table, which is taken from some of the irrigation experimentscarried on at the Utah Station:--
Effect of Varying Irrigations on Crop Yields Per Acre
|Depth of Water Applied (Inches) ||Wheat |
|Sugar Beets |
|5.0 ||40 || || ||194 ||25 |
|7.5 ||41 ||65 || || || |
|10.0 ||41 ||80 || ||213 ||26 |
|15.0 ||46 ||78 || ||253 ||27 |
|25.0 ||49 ||77 ||10,056 ||258 || |
|35.0 ||55 || ||9,142 ||291 ||26 |
|50 ||60 ||84 ||13,061 || || |
The soil was a typical arid soil of great depthand 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 soilproduced forty bushels of wheat. Doubling this amount of irrigation water producedonly forty-one bushels of wheat. Even with an irrigation of fifty inches, or tentimes that which produced forty bushels, only sixty bushels of wheat, or an increaseof one half, were produced. A similar variation may be observed in the case of theother crops. The first lesson to be drawn from this important principle of irrigationis that if the soil be so treated as to contain at planting time the largest proportionof the natural precipitation,--that is, if the ordinary methods of dry-farming beemployed,--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 thanto cover one acre to a depth of fifty inches, for in the former case four hundredbushels and in the second sixty bushels of wheat would be produced. The farmer whodesires to utilize in the most economical manner the small amount of water at hisdisposal must prepare the land according to dry-farm methods and then must spreadthe water at his disposal over a larger area of land. The land must be plowed inthe 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 goodresults by planting the rows twice as far apart as is ordinarily the case and bybringing the irrigation furrows near the rows of plants. Then, to make the best useof the water, he must carefully cover the irrigation furrow with dry dirt immediatelyafter the water has been applied and keep the whole surface well stirred so thatevaporation will be reduced to a minimum. The beginning of irrigation wisdom is alwaysthe storage of the natural precipitation. When that is done correctly, it is reallyremarkable how far a small amount of irrigation water may be made to go.
Under conditions of water scarcity it is oftenfound profitable to carry water to the garden in cement or iron pipes so that nowater may be lost by seepage or evaporation during the conveyance of the water fromthe reservoir to the garden. It is also often desirable to convey water to plantsthrough pipes laid under the ground, perforated at various intervals to allow thewater to escape and soak into the soil in the neighborhood of the plant roots. Allsuch refined methods of irrigation should be carefully investigated by the who wantsthe largest results from his limited water supply. Though such methods may seem cumbersomeand expensive at first, yet they will be found, if properly arranged, to be almostautomatic in their operation and also very profitable.
Forbes has reported a most interesting experimentdealing with the economical use of a small water supply under the long season andintense 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 windmilllifted the water into a 5000-gallon storage reservoir standing on a support 18 feethigh. The water was conveyed from this reservoir through black iron pipes buried1 or 2 feet from the trees to be watered. Small holes in the pipe 332 inch in diameterallowed the water to escape at desirable intervals. This irrigation plant was underexpert observation for considerable time, and it was found to furnish sufficientwater 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 figtree, 9 eucalyptus trees, 1 ash, and 13 miscellancous, making a total of 87 usefultrees, mainly fruit-bearing, and 32 vines and bushes. (See Fig. 95.) If such a resultcan be obtained with a windmill and with water ninety feet below the surface underthe arid conditions of Arizona, there should be little difficulty in securing sufficientwater over the larger portions of the dry-farm territory to make possible beautifulhomesteads.
The dry-farmer should carefully avoid the temptationto decry irrigation practices. Irrigation and dry-farming of necessity must go handin hand in the development of the great arid regions of the world. Neither can wellstand alone in the building of great commonwealths on the deserts of the earth.