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<br />PrCjjt:.'C L I,.::mds <br /> <br />River, and they usually occur in relatively small tracts. Some <br />exceptions are found in the bottomlands south of the river where <br />some tracts are moderately large. On the terraces and uplands, <br />the irrigable lands are more contiguous and it is not uncommon <br />for the irrigable lands to occur in fairly large tracts. <br /> <br />At the upper end of the project area, the irrigable lands <br />are at elevation 5900 feet while at the lower end the elevation <br />is 5400 feet. <br /> <br />Since all of the irrigable land has been under irrigation <br />for many years, considerable work has already been done toward <br />developing it for efficient and uniform application of water. <br />Therefore, development costs will be low on all irri.gable lands. <br /> <br />SOILS <br /> <br />The 80ils of the service area are within the Great Brown <br />Soils group which occurs in the semiarid parts of the Great Plains <br />Region. Because of the low rainfall, all of the soils are immature <br />and all are calcareous throughout their profiles. For the same <br />reason (low rainfall), plant nutrients have not been leached from <br />the soils. Hence, inherent fertility is high and except for small <br />isolated areas, any sound soil building program will result in <br />adequate to abundant fertility levels. <br /> <br />Because of the varying parent materials and local topographic <br />conditions, soil textures and soil depths are significantly variable, <br />In the uplands the soils are residual and in the Model area, where <br />the parent material is largely Granerous Shale, the soils are <br />moderately well suited for irrigation. They are deep and friable <br />with the textures of the topsoils and subsoils ranging from clay <br />loams to clay. Beneath the soil profile is a relatively thick <br />layer of sandy, weathered shale which provides adequate subsurface <br />drainage, <br /> <br />Other upland areas, confined largely to areas served by the <br />Chi os a 1I and Johns Flood ditches, have soils developed from Pierre <br />Shale. The topsoils and subsoils are similar in texture to those <br />developed on Granerous shale except they are less friable and lack <br />the sandy substratum below the subsoil. The project soils developed <br />from Pierre Shale are ill-adapted to irrigation because of their <br />weak structure and restricted subsurface drainage. <br /> <br />li The Chicosa'Ditch is part of the Baca Joint area. <br /> <br />29 <br /> <br /> <br /> <br />....,'~ <br /> <br />.C"; <br /> <br />'. ".,," <br />