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Another reason agronomic criteria are of limited value in reclamation is that the <br />majority of Trapper Mine is [o be returned [o rangeland and rangeland plant spe- <br />cies react in a different manner [o fertilizer levels than do annual crop plants. <br />Nearly all papers on range fertilization report favorable biological results but <br />broad and often unpredictable variations (Heady 1975). Duncan and Hylton (1970), <br />based on an extensive review, described results of range fertilization which var- <br />ied because of yearly climatic variations, soil series, growth habits of the <br />plant species, stage of plant maturity at [he time of sampling, plant parts sam- <br />pled, fertilizer rates and types, sampling methods and reporting units, season of <br />fertilizer application, and means by which the fertilizer was applied. An almost <br />infinite number of permutations of these causes of variation, many of which <br />remain unmeasured, complicates summarization of results Erom rangeland fertiliza- <br />lion. The major causes of uncertainty about responses to range fertilization <br />appear to be the variation of soil deficiencies from place [o place and the fluc- <br />tuation of responses with changes in rainfall and temperatures. <br />Nitrate-Nitrogen (See Tables 2.7-6 and 2.7-7) <br />Nitrogen (N) expressed as nitrate-N is an indicator of immediately available <br />inorganic nitrogen for plant growth. Avast majority of nitrogen in a soil is <br />usually unavailable for plant utilization and is gradually released by minerali- <br />zation of organic matter. With the decomposition of organic matter through time <br />and weathering, plant available nitrogen is released. Spoil, however, is usually <br />devoid of organic matter except for coal or carbonaceous shales that may be mixed <br />in and the availability of the nitrogen released from this spoil organic matter <br />may not be as great as that obtained from organic material found in topsoil. <br />Therefore, plant available N is frequently deficient in mine spoils (Berg, 1974). <br />N measurements are usually no[ valid for coal spoils either because of the carbon <br />in Che coal or carbonaceous shales usually present in spoil samples (Berg, 1974). <br />Thia usually produces a higher estimate of N than actually exists. Low estimates <br />however, could be relied upon as an indication of a N deficiency. <br /> <br />2-380 <br />