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Show IRRIGATION IS NEEDED Where Rainfall Is Less Than Ono Inch in Fifteen Days. One of Main Advantages Is That Water Wa-ter Supply Required for Growth of Crops Is Largely Under Control Con-trol of Grower. (By MILO B. WILLIAMS. United States Department of Agriculture.) A climate having an annual rainfall rain-fall of 20 inches or more is generally regarded as humid, for where this amount of rain is fairly well distributed distrib-uted throughout the year arable land can usually be farmed. This measure meas-ure of aridity divides the United States into two nearly equal parts, east and west, marked by a belt of semiarid country located near the ninety-ninth meridian. Although this division is based upon the moisture supply of the climate, it is not a true Index of the need of Irrigation, as many sections having an annual rainfall rain-fall of more than 20 inches do not during dur-ing the growing season receive a dependable de-pendable precipitation sufficient for farming purposes. Rains must come at such times and in such amounts as will properly moisten the soil for the preparation of the seed bed and will furnish a' reasonably constant supply of moisture to germinate the seed and develop the plant until it reaches maturity. ma-turity. A check in this supply of soil moisture at any stage of the growth .affects the quality and quantity of the yield and may greatly reduce the prof-Its prof-Its of the grower. The real test of what is a humid section is therefore not the total annual rainfall, but the monthly, and, in ' the case of many plants, the weekly amount during the growing season. Viewed in this light, Irrigation becomes a national need rather than rrely a western practice. prac-tice. There is pe'taps no other industry 60 broad or so varied as farming. No manufacturer encounters so many uncontrolled un-controlled elements and no factory putput Is so delicate or perishable or Its market so uncertain as that of the farmer. One of the main advantages of farming under Irrigation is that the water supply needed for the growth of crops, which is one of the most, if not the most, uncertain factors in other farming, is very largely under the con trol of the grower. This advantage, however, has hitherto scarcely been grasped by the farmers in the humid section, and few realize that with a small outlay an irrigation plant can be Installed which will insure them against complete or partial crop failures fail-ures during droughts. Farming conditions, however, have greatly changed in recent years. The soils in many localities no longer produce pro-duce profitable yields without the application ap-plication of artificial fertilizers; the value of farm lands has greatly increased; in-creased; farming methods are more intensive; more valuable crops are being grown; and consumers are demanding de-manding a greater variety, a better quality, and a more constant supply of delicate farm products. Thus, the farmer of today is obliged to expend a large amount of money to produce a crop, and if for any cause this crop is a failure his losses are greater than in the past. The wheat grower of Kgnsas may produce a crop at an average av-erage cost of $10 per acre, while the citrus grower of southern California Is obliged to spend $400 per acre in growing and marketing a crop of navel oranges?. To insure the wheat crop against a possible drought might not pay, while to Insure the orange crop is an absolute necessity, for if the pumping plants which raise water from the bed of the Santa Ana river , for the orange orchards of Riverside. Cal., were to he shut down that region would in time revert to a desert. Although Al-though the annual precipitation in the citrus regions of Florida is 55 inches, while that at Riverside is only 10.74 inches, one should not conclude that irrigation is not necessary in the former, for-mer, as there are periods when less than 1 inch of rain falls In 30 days, and at such times the application of a small amount of water may be followed follow-ed by as good results as at Riverside. River-side. Under average conditions it is safe to say a drought occurs whenever the precipitation In any 15-day period falls below 1 Inch. It has been the writer's obseravtion' that crops will usually suffer if they do not receive considerably consider-ably more than this amount of rain, especially during the spring and early summer months. Later in the season this quantity may not be needed, excepting ex-cepting for late garden truck and some fruits. |