Arizona sentinel Yuma southwest., 1916-04-20
Special to the Yuma Daily Examiner

w WASIlilNS OlN, ApllI Al Under conditions such as prevail in Idaho on a normal project with medium clay foam, irrigated land should be supplied with sufficient water during the season to enable each irrigated acre to retain 2 feet, according to a recent investigation of the U. s. Department of Agricul- ture.
 This applies, it is said, to at least 75 per cent of the lr- projects in Idaho and probably to as large a per cent of the projects in other states.
 In order that the land may retain the needed feet of water per acre, the farmer should receive about "A feet on medium clay and sandy loam soils. Where the soil is porous or has a porous subsoil lying closer to the surface than feet, more than this quantity of water should be de livered to the consumer, the exact quantity of water should be deliver ed to the consumer, the exact quan- tity depending, of course, upon the porosity of the soil.
 Where an Idaho project is devoted one-half to grain and the other half to alfalfa or other crops, the total vol ume of water should be distributed something as follows: 1S.7 per cent during May, 2S per cent during June, BPS per cent during. July, 17.2 per cent during August, and per cent during the first half of September. After this time the only demand for water is for livestock and domestic purposes.
 These conclusions, which are based upon cooperative experiments con ducted by the II. s. Department of Agriculture and the State Land Board of Idaho, are reported in new Pro- fessional Paper, No. 339, of the U. s. Department of Agriculture, entitled
 Experiments on the Economic Use of Irrigation Water in Idaho" by Don H. Bark. During the course of this investigation the water was measured upon 529 individual tracts covering a total area of slightly over $500 acres. The land was used of r staple crops, alfalfa, clover pasture, spring and winter grains, potatoes and or chards.
 Experiments show that the yield of grain on the heavier soils such as clay, clay loam, sandy loam, and fine sand, will normally increase with the supply of water until an amount vary ing between IA and IS acre-feet has been applied After this the applica- ton of more water will decrease the yield of grain and in many cases the yield of straw as well. Alfalfa re- quires larger quantities of water and the experiments did not reach a point at which an increased supply began to lessen the yield. If the yield alone is considered it is difficult, it is said, to apply too much water to alfalfa, provided no more is applied at one time than the soil will promptly ab sorb With both grain and alfalfa, however, the amount of water that it is profitable, from a business point of view, to use depends upon the relative cost of land and of water and other local economic conditions.
 With potatoes, it is found that there is strong tendency for the yield to increase with the supply of water. The rate of increase, however, grew smaller as the quantity of water was increased, and on clay loam soils it probably will not be advisable to ap ply more than or 21a feet per acre to the crop.
 The report also deals with the question of the proper quantity of water to apply at each irrigation. An unavoidable loss from evaporation in- variably occurs during and immediate ly after irrigation and it is, therefore, desirable to have no more applications during the season than are required 10 maintain the needed moisture content in the soil Investigators found that from to acre-inches at one application is the correct Quan- tity. Impervious soils should be so manipulated that they will absorb the smaller amount at least, while on the porous soils large irrigation heads should be used. On these porous