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35 D <br /> r <br /> stabilization are very difficult and costly. Topdressing with better material is necessary to <br /> establish and maintain vegetation. <br /> (d) The major properties that influence erosion and stability of the surface and the 0 <br /> productive potential of the reconstructed soil are listed in the guide (Table 620-1 1.) <br /> (e) Excessive amounts of substances that restrict plant growth, such as sodium, O <br /> salt, sulfur, copper, and nickel, create problems in establishing vegetation and, therefore, <br /> also influence erosion and the stability of the surface. Other substances, such as <br /> selenium, boron, and arsenic, get into the food chain and are toxic to animals that eat the (� <br /> vegetation. Of all these substances, only sodium and salt are criteria in the guide. If l J <br /> relatively high levels of toxic substances are in the reconstruction material, the material a <br /> should be rated poor. Laboratory tests may be needed to properly identify toxic <br /> substances. <br /> (f) Materials that are extremely acid or have the potential upon oxidation of <br /> becoming extremely acid are difficult and expensive to vegetate. They also contribute to <br /> poor water quality, both in runoff or in' ground water. Materials high in pyrite and <br /> marcasite without offsetting bases have high potential acidity. Laboratory tests may be <br /> needed to properly identify these materials. <br /> (g) Vegetation is difficult to establish on soils that have high pH. Many of these <br /> soils also have a high sodium adsorption ratio which indicates potential instability and 0 <br /> water transmission problems. D <br /> (h) The available water capacity also is important in establishing vegetation. Soils <br /> that have a low available water capacity may require irrigation for establishment of <br /> vegetation. <br /> (i) The stability of the soil depends upon its erodibility by water and wind and its <br /> strength. Water erodibility is indicated by the K factor; wind erodibility is rated according <br /> to the "I Value" of the wind erodibility group. Potential slippage hazard is related to soil <br /> t. <br /> (430-VI-NSH, Draft, September 1992) <br />