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Mesa Soils The mesa soils have developed primarily from aeolian deposits over glacial till. They are medium textured in the surface, moderately fine textured in the subsoil, slowly permeable, and deep over gravel and robble. A small sector in the northern part of the mesa has aeolian deposits on Animas shale or over soil developed from Animas shale. The topography of the mesa is gently to moderately rolling and the soils, unless protected, are susceptible to erosion by water and wind. Some areas of small extent, usually cultivated swales, within the project are intermittently seeped. This is due primarily to an accumulation of water as a result of inadequate removal of tail water and lateral movement of subsurface water from excessive irrigation. Larger areas with similar conditions have been excluded from the project. In general, the soils are more than 60 inches deep, have a high water-holding capaci ty and slow permeabil i ty. Generally the soils in the northern part of the mesa have a higher organic matter content. River Valley Soils The river valley is a typical small river flood plain. It is com- posed of a complex pattern of soils that have developed on low river terraces, and others that have developed on alluvial fans from small tributary drainages. Alluvium from the upper watershed is the source of material from whi ch the soils adjacent to the river and those on the river terraces have developed. These soils range in depth from 10 to 36 inches over gravel and robble. The fan so ils have developed from local alluvium and colluvium of sandstone and shale origin. These materials influence the textures which vary from loam to clay loam. Depth of these so i Is over gravel and cobble is generally greater than the other soils in the river bottom area. In years of high runoff, soils adjacent to the river may be flooded. Also in a few low spots the water table is wi thin 30 inches of the surface. Terrace and fan soils generally are free from overflow and water table. Soils in the northern part of the river valley are usually darker and have more profile development. All the soils in the project require nitrogen and phosphorus fertilizer. For maximum effectiveness of the fertilizer, care must be exercised in applying irrigation water. This may require a revision of farm irrigation systems and additional land development. Soils were grouped into land capability units as well as evaluation areas. The acreage by these units within each evaluation area is listed in table 2. General soil characteristics for each land capability unit are shown in table 3. These units, tabulated by evaluation areas, allow a general appraisal to be made of each evaluation area and of differences between evaluation areas. - 9 -