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<br /> <br />~ maintenance fertilization ma be re wired for <br />y q perhaps 30 yr. <br />Without organic matter to absorb the nutrient, it is e';timated that <br />two applications each year, of about 30 lb nitrogen/acre, would be <br />required to initially maintain vegetation. <br />Sewage sludge, applied to mine waste in excess of 5 tonsjacre, F~rovides more <br />nitrogen than can be held by the soil. In the harsh climate at 3,354 m <br />(11,000 ft), the half-life of nitrogen in sewage sludge may range from <br />2-4 yr. Twenty tons of sewage contains roughly 1,200 lb of nitrogen. If <br />half of that were to become available for plant use within two years, the <br />result would be similar to applying 300 lb of nitrogen per acre per year to <br />vegetation requiring only about 60 lb of nitrogen per acre per year. This <br />would be a gross overapplication of nitrogen. <br />Wood chips have a high carbon-to-nitrogen ratio (about 90:1). foil organic <br />matter, the desired product, has a carbon-to-nitrogen ratio of about 10:1. <br />Microbial decomposition of the wood requires large quantitates of nitrogen <br />and uses the excess nitrogen from the sewage to form humus. Tlius, much of <br />the excess nitrogen is retained in the soil and the sewage and wood chips <br />complement each other. Using the combination of wood chips and sewage, a <br />significant quantity of nutrients and organic matter can be applied at one <br />time. (Particular care must be taken to insure the proper proportion of <br />wood chips to sewage. Soil microbes easily out compete plants 1`or nitrogen <br />by immobilizing the nutrient during decomposition. Without sufficient <br />nitrogen for both microbes and plants, vegetation will undergo nitrogen <br />deficiency.) <br />The benefits derived from each waste product, when used separately as a soil <br />builder, are limited; however, when applied together, two products (sewage <br />sludge and wood chips), can complement one another. <br />Test Plots <br />Test plots were established on the Urad Mine tailing in 1972, 1973, and <br />1974. Various combinations and quantitates of fertilizer, soil amendments, <br />and irrigation were applied. <br />5 <br />