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• <br /> <br />I• <br />permeability, erodibility, surface crusting, and seedling emergence. SAR reveals the relative <br />dominance of sodium in the soil water solution whereas ESP reflects the exchangeable (reserve) <br />sodium on the soil particle surface. These tests are complimentary and often interchangeable <br />(USDA, 1969). ESP is often determined only when the SAR is greater than 11. <br />Dominant Water Soluble Anions (Carbonate. Bicarbonate. and Sulfate), Sulfate is used in the <br />formation of many proteins and is therefore essential for both plants and animals. Sulfur is needed <br />by plants in about the same quantities as phosphorous. Spoils within the Northern Great Plains Coal <br />province are typically high in sulfate. (Barth et al., 1977). The sedimentary rocks in association with <br />coal seams will often yield substantial amounts of sulfate ions through the oxidation of pyrite and/or <br />marcasite. Sulfuric acid produced in the oxidation of pyrite and marcasite is commonly dissociated <br />and buffeted by the bicarbonate and carbonate ions dissolved from the associated carbonate rocks, <br />thus liberating sulfate ions into solution. The major portion of sulfate found in spoils may be derived <br />from the dissolution of gypsum. <br />The bicarbonate and carbonate ion content or alkalinity is generally a measure of buffering capacity. <br />Common sources of these anions are the solution of carbonate rocks, digenesis of CO2 from organic <br />compounds, and COZ from the atmosphere and soil. The presence of bicarbonate verses carbonate <br />is usually determined by the pH. Above a pH of 8.2, bicarbonate ions dissociate to carbonate ions. <br />Below a pH of 4.5, most of the bicarbonate ions are converted to carbonic acid (HZCO3). In between <br />these two values, carbonate ions will normally add H+ ions to become bicarbonate ions (Dollhopf et <br />al., 1981). <br />Carbonates and bicarbonates also increase the sodium buildup hazard in soils by precipitating <br />calcium and magnesium as carbonates which have an extremely low solubility. Elevated levels of <br />bicarbonate in soils (i.e., 10 megA) can also adversely affect sensitive crops (Traynor, 1980). <br />Ammonium and Nitrate Nitrogen. Three major forms of soil nitrogen are typically found in the soil <br />environment: 1) organic nitrogen associated with soil humus, 2) ammonium nitrogen associated with <br />clay minerals and organic matter, and 3) soluble nitrate compounds. Most of the soil nitrogen is in <br />the organic form and is slowly released, through microbial action, as ammonium and nitrate. This <br />nitrification process requires nitrifying bacteria, a carbon source, oxygen, water, and favorable soil <br />Revised 9/99 2.04.6-75 <br />