1986-12-08_GENERAL DOCUMENTS - M1977493 (2)

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13 These data indicate that several methods are available for stabilizing mill tailings at costs of less than $400 per acre. The chemical-vegetative ; procedure appears to be cheapest and wherever applicable should be a preferred method. Both the chemical-vegetative and hydroseeding methods appear to be cheaper than the matting or soil-covering procedures. However, for difficult areas these latter methods may be mandatory. ONGOING BUREAU OF MINES RESEARCH Development of several different vegetative procedures has provided satis- fi'k. , factory stabilization for many of the mill tailing accumulations scattered across the country. However, means of reducing maintenance costs on vegetatedh! ble and more economical procedures are needed for vegetat- ing highly saline, acid, or alkaline tailings. Reduction of fertilizer requirements is being studied to reduce maintenance costs. To overcome the salinity and other problems, work is being done on seedbed preparation, plant- ing, and watering practices. Research also is continuing on making synthetic ; '^ soils from the tailings by adding sewage sludge or refuse compost. Reducing Maintenance Costs ! Practically all mill tailings are deficient in fertilizer elements, espe- cially nitrogen. Nitrogen not only is low in most tailings, but it is also ; .. readily depleted from vegetated wastes containing heavy metal salts. Lack-of nitrogen can be overcome by planting nitrogen-fixing legumes, but legume growth on tailings is difficult to perpetuate. Growth of nitrogen-fixing native plant species that may be compatible 'n s is being with the harsh environment of tailings g investigated. Particular attention is being given to Indian ricegrass , a desert-type plant that fixes nitrogen in a root sheath of sand particles invaded by bacteria or other micro- organisms. Obtaining growth from Indian ricegrass , however, is difficult to { achieve in that the seeds contain a natural inhibitor that limits germination 1 to 1 percent or less on newly matured or up to 2-year-old seeds. Ricegrass seeds have been gathered during the past 3 years and germination studies made in an effort to break the dormancy. Treatments by attrition grinding with quartz to break the seed covering, sulfuric acid and water soaking and boiling, and cool and below freezing incubation were all ineffective when treating both newly matured and 2-year-old seeds. When soaking seeds less than a year old in 70-percent-by-volume sulfuric acid for 25 minutes at 25° C, germination was nil; and with a subsequent 24-hour soaking in lC3 molar gibberellic acid or kinetin hormones in a solvent of 9 parts of dichloromethane and 1 part ethanol (1 cc solution per 100 seeds) , the germination was still less than 5 percent. However, when using an acid soak followed by a soak in both gibberellic acid and kinetin, the germination after 2-, 4-, and 6-week intervals, was respec- tively, in percent, 55, 75, and 90. When treating 2-year-old seeds , treat- ments with an acid soak plus respective treatments with kinetin, gibberellic acid, or gibberellic acid plus kinetin gave 5-week germination percentages respectively of 5, 80, and 80. After 2 year's of aging, the inhibitor effect decreases and kinetin treatment is no longer necessary.