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Show Alfalfa Needs Huge Quantities Water To make one pound of dry alfalfa hay,- the growing plants need to absorb ab-sorb -and: later give off or trams pire . from-500' to 750 pounds of water. Ir- . rigation engineers use the term 'transpiration ratio" and say that alfalfa.' al-falfa.' has a transpiration ratio of from 500 to 750, the smaller ratio for a cool, moist' climate, and the larger for hotter, dryer sections. Phrasing it another way, engineers of the United States Department of Agriculture, find that to produce five tons of dry alfalfa hay an acret in western Oregon' about 20 acre inches of water a year will be required; that is, the alfalfa will remove from the soil as much water as would be needed need-ed to coyer. the field to a' depth of 20 inches,., allowing only a moderate quantity for direct evaporation from the .soil. In the Willamette valley of Oregon, Ore-gon, for example, according to M. R. Lewis of the bureau of agricultural engineering, the 20 inches of water required might be made up of seven inches stored .in the soil from winter rains, three inches from rains occurring occur-ring in the growing season, and 10 inches supplied by irrigation. The proportions would vary with the season. sea-son. In more arid regions alfalfa may need as much as 30 inches of water, or even ' more, to produce five tons of dry hay per acre, because the de-mam'.s de-mam'.s for both evaporation and transpiration are greater. To produce annually such crops as are raised in some sections, say eight or ten tons an acre, the requirement will be roughly proportional to that for the five ton crop in eastern Oregon. . Different crops vary widely in their water requirements. In a section sec-tion where- it takes about 20 acre inches to grow a five ton crop of alfalfa al-falfa an acre, it has been found that it takes 12 inches for corn or beets, about 16 inches for potatoes, and only ' about nine inches for white beans. If a crop does not get its full r.ropor transpiration ratio it will not manufacture its full quota of marketable market-able product. , |