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Nn tendency towards mass movement within areas mapped was noted but the potential is moderate. Anv • changes in supplemental water on sloping areas will increase movement possibilities. Chemical Properties and Natural Fertility -The soils of mapping unit number 17 have the same chemical properties and natural fertility description as the soils of mapping unit number 16. However, laboratory values may vary slightly. ManninG Unit Number 18 - Moderately deep (20 to 40 inches to bedrock) and deep (more than 40 inches to bedrock), light colored, gravelly and cobbly, fine textured (more than 35 percent clay), maturely developed soils having horizons o! secondary silicate clay accumulation (B2t horizons) and occurring in parts of the study area where the mean summer soil temperature (June, July, and August temperature measured at 20 inches) is 59° or warmer. Classification of ~9aior Comnoncnts The components listed below comprise the major part of the mapping unit A. Ustollic Haplargids (Brown Soils). 1. Clayey-skeletal, montmorillonitic, mesic (Nehar Series) Extent and Maior Areas of Occurrence Soils of mapping unit number 18 occur in small acreage in the study area and is found principally on the steeply sloping edges of mesas and hills in the southwestern part of the study area west of Minnesota Crcck. • Characteristic TonoGranhv Soils of mapping unit number 18 occupy moderately to steeply sloping edges of mesa-like areas believed to he remnants o(old geomorphic fans. Slopes range from 10 percent to 60 percent and are usually relatively uniform. Physical Proncnies The soils of mapping unit number 18 are mature soils having a strong, stable, blocky and granular structure. They are also fine-textured and contain at least 35 percent gravel, cobble, and stone. Structural properties which are essential to water, air, and plant root movement are absent in these soils. Their steep slopes and composition of coarse fragments make them poor choices for seedbed material. The fine-textured portion of these soils have a high shrink/swell ratio but this is offset by the coarse fraemcnt content. No mass movement tendency was noticed in this unit: however, the potential for such movemen[ is moderate. Am• changes in soil moisture at higher elevations can chance this status. In their native state, the soils of this unit arc moderately susceptible to accelerated water erosion, particularly where natural vegetation has been depleted. They are not very susceptible to water erosion. If cleared or disturbed they arc very susceptible to accelerated water erosion and moderately susceptible to wind erosion. Activities involving disturbance of these areas should include erosion control practices. Chemical Properties and Natural Fertility -These are moderately weathered, mature soils having distinct . Genetic horizonation including horizons of silicate clay accumulation but lacking consistent horizons of secondary carbonates. The cation exchange complex (ability of some parts of the soil to hold and exchange