Alfalfa was first planted and cared for by half-civilized man long before any history was written. In spite of the fact that its line of descent has come thru the Medes and Persians by way of the Greeks, the Romans, the Moslems, and the Spaniards,--in spite of long sojourns in many lands, the heritage is still undefiled. Instead of losing in adaptability, possibly long centuries of trial have made it more fit. At any rate, here it is: high in power to yield, rich in power to nourish.
With its deep roots it laughs at drought and mellows up the subsoil. Its perennial habit enables it to furnish hay, pasture, or seed for several years in succession. Most important of all, however, is its power to take nitrogen from the air and store this essential plant-food element in its roots. Wisdom in crop rotation and livestock growing, intelligence in utilizing alfalfa on the farm, and care in handling manure and irrigation water are all strong links in the chain of permanently profitable agriculture.
In western America, as in arid regions generally, alfalfa is the basis of good farming. Cattle grazing and wheat growing may flourish as lone industries for a time, but in the end they must give way to a diversified and somewhat intensified agriculture. Cattle require feed in winter; wheat must eventually become part of some sort of cropping system; repeatedly tilled land must in the end be replenished. Wherever the rainfall is light, the soils rich in lime, and the climate temperate, there alfalfa will become the foundation of intelligent agriculture.
Stewart, George, "Circular No. 45 - Alfalfa Production Under Irrigation" (1921). UAES Circulars. Paper 39.