The best soils for alfalfa are those of the Western mountain States, and in these the deposit soils of the river valleys stand among the foremost. These soils are usually of much depth. Many of them have water underneath, and the subsoil is usually so porous that the roots can go far down in them, such is the character of nearly all the bottom land west of the Mississippi. But in nearly all of the mountain region of the West, from Banff in British Columbia to Mexico, alfalfa will grow well under irrigation, or in the absence of irrigation, if ground water is not too distant from the surface. In this region alfalfa grows more vigorously and more persistently than in almost any other portion of the United States. In regions where alfalfa is not dependent upon irrigation, the best soils probably are deep, rich calcareous loams, clay or sandy, and underlaid with what may be termed a mild or reasonably porous clay subsoil. With such soils the plants may be in no way influenced by sheet water below, as on some of these in Nebraska, for instance, such water is fully 150 feet below the surface. These soils are usually possessed of abundant food supplies to nourish the plants, and the roots can go far down into the subsoils to gather food and moisture. Such lands are found more or less in nearly all the States of the Union east from the Rocky Mountains; hence, when the requisite bacteria are present, good crops can be grown on them in every State in the Union. On the ordinary black soils of the prairie, alfalfa will usually grow reasonably well if underlaid with clay not too distant nor too tenacious. When the roots get down into the subsoil, they can usually find much food in the same, and unless in very dry areas a sufficiency of moisture, but in many instances it may be necessary to introduce the requisite bacteria, and to apply farmyard manure to encourage sufficient growth to carry the roots down quickly to the subsoil. In some prairie soils the growth will be vigorous from the start, but usually these are lands that have grown hardwood timber, and that have in them more or less clay. In climates where the rainfall is considerable, alfalfa will frequently grow well on gravelly soils and on those that are stony. Some of the best alfalfa soils in the State of New York, New England States, and in the Canadian provinces of Quebec and Ontario are of this character.