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35 • ~ I <br />stabilization are very difficult and costly. Topdressing with better material is necessary to <br />establish and maintain vegetation. <br />Id) The major properties that influence erosion and stability of the surface and the <br />productive potential of the reconstructed soil are listed in the guide (Table 620-11 .) <br />(el Excessive amounts of substances that restrict plant growth, such as sodium, <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 <br />relatively high levels of toxic substances are in the reconstruction material, the material <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 />Ig) 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 <br />water transmission problems. <br />Ihl 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 (actor; wind erodibility is rated according <br />to the "I Value" of the wind erodibility group. Potential slippage hazard is related to soil <br />1430-VI-NSH, Draft, September 19921 <br />