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• (reserve) sodium on the soil particle surface. These tests are complimentary and often <br />interchangeable (USDA, 1969). ESP is often determined only when the SAR is greater than 11. <br />Dominant WaterSoluble Anions (Carbonate. Bicarbonate. and Sulfatel. 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 <br />Coal province are typically high in sulfate. (Barth et al., 1977). The sedimentary rocks in <br />association with coal seams will often yield substantial amounts of sulfate ions through the oxidation <br />of pyrite and/or marcasite. Sulfuric acid produced in the oxidation of pyrite and marcasite is <br />commonly dissociated and buffeted by the bicarbonate and carbonate ions dissolved from the <br />associated carbonate rocks, thus liberating sulfate ions into solution. The major portion of sulfate <br />found in spoils may be derived from the dissolution of gypsum. <br />The bicarbonate and carbonate ion content or alkalinity is generally a measure of buffering <br />capacity. Common sources of these anions are the solution of carbonate rocks, digenesis of COz <br />from organic compounds, and CO2 from the atmosphere and soil. The presence of bicarbonate <br />verses carbonate is usually determined by the pH. Above a pH of 8.2, bicarbonate ions dissociate <br />• to carbonate ions. Below a pH of 4.5, most of the bicarbonate ions are converted to carbonic acid <br />(H2CO3). In between these two values, carbonate ions will normally add H+ ions to become <br />bicarbonate ions (Dollhopf et 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 meg/I} can also adversely affect sensitive crops (Traynor, 1980). <br />Ammonium and Nitrate Nitrogen. Three majorforms of soil nitrogen are typically found in the soil <br />environment: 1) organic nitrogen associated with soil humus, 2) ammonium nitrogen associated <br />with clay minerals and organic matter, and 3) soluble nitrate compounds. Most of the soil nitrogen <br />is in the organic form and is slowly released, through microbial action, as ammonium and nitrate. <br />This nitrification process requires nitrifying bacteria, a carbon source, oxygen, water, and favorable <br />soil temperatures. Nitrate and ammonium analyses are generally determined on overburden and <br />interburden material which will serve as a growth or aquifer medium. Nitrogen levels influence soil <br />productivity as well as ground water quality. <br />• Revised 27 Aug 2002 16 <br />