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<br />Project Lands <br /> <br />The soils of the terrace positions have developed from alluvial <br />materials. They are deep friable soils with stable blocky to <br />slightly prismatic structure in both the topsoil and subsoil. The <br />topsoils are quite uniform with respect to texture, the most prevalent <br />type being clay loam. The subsoils are also quite uniform--the <br />texture generally being either a loam or silt loam. However, in <br />some instances the texture was found to be sandy loam. <br /> <br />The substrata of the terrace soils average about 10 feet in <br />thickness, Their textures are clay loam and very fine sandy loam, <br />and the structure is granular. The substrata are sufficiently <br />pelweable to provide adequate subsurface drainage. <br /> <br />The bottomland soils have also developed from alluvium which <br />consists of heterogeneous mixtures of materials deposited by the <br />river and by side drains. These soils are deep but are not well <br />adapted to irrigation because of fine textures and poor development <br />of ,soil structure. <br /> <br />..) <br /> <br />The topsoil is predominantly heavy clay loam and the subsoil <br />is generally clay or heavy clay loam. The soil substrata are also <br />fine textured, The most extensive type of material is clay, however, <br />heavy clay loam is also widespread. <br /> <br />The soil structure, although somewhat indistinct, is blocky <br />and has not deteriorated under water saturated conditions. <br /> <br />Because of the fine texture and poorly developed structure, <br />these soils are inadequately aeriated;therefore, crop yields are <br />low. None of the soils met the test of arability except in areas <br />having coarse textured substrata which would provide adequate <br />subsurface drainage. <br /> <br />','.' <br /> <br />SALINITY AND ALKALINITY <br /> <br />,:;-;,17: <br /> <br />No significant problems from saline and alkaline soils are <br />expected to develOp from sustained irrigation on about 70 percent <br />of the irrigable land. These lands, although irrigated in the past <br />under short water supply conditions, have remained free of harmful <br />accumulations of salts and alkali. In future operations the quality <br />of water will be slightly improved and the application of greater <br />supplies will result in greater leaching. Because drainage is <br />adequate, these soils are expected to remain free of harmful <br />accumulations of salts and alkali. <br /> <br />30 <br />