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4214 . The alluvial soils of recent deposition occupy the lowest topo- graphic position, adjacent to the Arkansas River and tributary streams. Much of the first bottom land along the main stem of the Arkansas is underlain by a sandy and gravelly substratum which is usually absent in the valleys of the small tributary streams. The bottom lands have many factors that limit their use for irrigated agriculture including flooding, drainage restrictions, high salinity, high water tables, and heavy' textures. Terrace soils border the bottom lands and occupy a higher topo- graphic position. They have been formed from very old alluvial deposits. The inner or riverward edge of the terrace is usually marked by a steep gravelly slope where the terraces are low, and by nearly perpendicular shale or limestone bluffs capped with gravel where the terraces are high. The majority of the terrace soils are deep mature soils underlain by the sandy or. gravelly parent material. The upland soils are of residual, alluvial, and aeolian origin. In the eastern portion of the project service area, on the north, side of the Arkansas Valley, between the town of Hasty and the Colorado-Kansas state line is a large body of upland loessial soils. The upland soils in the central and western portions of the pro- ject service area between Pueblo and Las Animas have developed from very old alluvial or residual sources. In the central portion, upland soils also occur on the south side of the river. The8P ~rp ~hp mnst desirable of the upland soils due to their depth.' Their parent material was a soft sandy shale. In the central section on the north side of the Arkansas River in the vicinity of Ordway and Sugar City, the soils have been derived from a soft sandy shale which is highly gypsiferous. They are heavy to medium textured soils. Upland soils derived from very old alluvium s~diments of medium texture are more widely distri- buted, principally in the areas served by the Holbrook Canal and the western portion of the area served by the Colorado Canal in the vicinity of Crowley and Olney Springs. These soils tend. to have texture variation in the soil profile. . Land classification is the systematic appraisal of lands and their designation by categories on. the basis of similar characteristics. The classification is conducted for the specific purpose of establishing the degree of suitability of land for irrigation. ~uitability connotes a reasonable expectancy of permanent profit- able production under irrigation. Four classes of land were 111-27 .