. Principles of agricultural chemistry [microform] . Series.—Compact adobe-like gray to dark or brown soils and subsoils,formed mainly by reworking of sandstones and shales andoccupying old elevated stream terraces. This is an importantseries adapted to alfalfa and general farm crops and stock raising; PHYSICAIv COMPOSITION AND CLASSES OF SOILS 99 also used to a considerable extent in the production of sugar beets. Arid Southwest.—Gila Series.—Light to dark brown soils offlood-plain alluvium underlaid at varying depths by coarse sandsand gravels. Under favorable irrigation and drainage conditi
. Principles of agricultural chemistry [microform] . Series.—Compact adobe-like gray to dark or brown soils and subsoils,formed mainly by reworking of sandstones and shales andoccupying old elevated stream terraces. This is an importantseries adapted to alfalfa and general farm crops and stock raising; PHYSICAIv COMPOSITION AND CLASSES OF SOILS 99 also used to a considerable extent in the production of sugar beets. Arid Southwest.—Gila Series.—Light to dark brown soils offlood-plain alluvium underlaid at varying depths by coarse sandsand gravels. Under favorable irrigation and drainage conditions,the members of the Gila series are adapted chiefly to the produc-tion of alfalfa, potatoes, truck, and root crops. Pacific Coast.—Fresno Series.—Light-colored soils with light-gray, ashy subsoils and alkali-carbonate hardpan, derived fromold alluvial wash. Where protected from alkali accumulations,these soils have been very successfully used for vineyards andraisin grapes, and are particularly adapted to almonds, peaches,and Fig. 28.—Photograph of a soil map, Willis area, Texas. Soil Survey.—The soil surveyor is provided with a map, com-pass, measuring instruments, and soil sampler. After a generalinspection has been made, and the provisional types decided upon,the mapping is begun. Preliminary borings in the soil are madeto outline the location of a body of soil of uniform is then colored in on the map. The surveyor then worksaway from this area until a different type of soil is encountered. lOO PRINCIPIvES OF AGRICULTURAL CHEMISTRY The line of separation between these two types (which mayconsist of a narrow strip of intermediate soil) is then outlined onthe map. Other areas are outlined in the same manner. The identification of the types is aided by physical is, of course, not possible to make a great number of types in agiven area, and a certain latitude must be allowed, between whichlimits the soil may vary. As a rule
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