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14 <br />Breaking the dormancy of Indian ricegrass seeds offers substantial prom- <br />ise for initiating this type of growth on adverse tailing materials, thus <br />offering the potential of reducing nitrogen fertilizer requirements and <br />related maintenance costs. Stands of Indian ricegrass are normally short- <br />lived, but should prepare the way for accession of other plants. Tests are <br />underway to determine if properly treated seeds can be germinated and growth <br />sustained in adverse tailing materials. <br />Vegetating Adverse Tailings <br />Practically all mill tailings contain deleterious inorganic salts, lack <br />organic components and essential nutrients, and do not have the physical <br />nature required for sustaining vegetative growth. For many tailings these <br />adverse conditions can be overcome in time by fertilization, gradual buildup <br />of organic and microbial populations by encouraging plant growth, and use of <br />chemicals for binding of the surface to prevent blowing of loose sands that <br />cut off or bury established vegetation. However, excessive salinity or acid- <br />ity presents more difficult problems. Combination problems can exist in which <br />tailings may be excessively saline, because of the recycling of processing <br />waters, and simultaneously contain sulfide materials such as pyrite that upon <br />.oxidation would drop the pH of the tailings to a low level in a~relatively <br />short time. Such a tailing is Kennecott's Utah Copper Division milling waste. <br />This material with a pH of 7.$, when fresh, contains salinity equivalent to <br />2.4 atmospheres osmotic concentration plus approximately 1.3 percent pyrite. <br />The salts in the tailings cause an osmotic gradient that transfers fluid from <br />the plants and thus vegetation dies of dehydratiott shortly after sprouting. <br />Another problem is that, if vegetation is planted on these tailings and irri- <br />gation of the plants leaches away the salts, the pyrite oxidizes and the pH <br />may drop from 7.8 to less than 3.0 within a month's time, Therefore, this'. <br />material was considered as a typical adverse waste and was used for laboratory <br />and small field testing. <br />Salinity and Heavy Metal Salt Problems <br />Salts present in the wastes or mill waters impede plant growth. Consid- <br />erable difficulty was encountered in growing vegetation in milling wastes from <br />Kennecott's Utah Copper Division. To determine the reasons, duplicate plant- <br />ings were made in (1) the normal flotation tailings, containing considerable. <br />water-soluble salts, but assaying only 0.05 percent copper, and (2) a simulated <br />tailing containing few soluble salts but almost 0.25 percent copper. In both <br />materials the copper was present mainly as the sulfide mineral, chalcopyrite. <br />Seeded test plots were watered 'with tapwater and tailings effluent water. <br />Both germination and growth were adversely affected when effluent water was <br />used. For samples watered with tapwater, germination and growth were much <br />better in the simulated tailing material despite the higher content of copper. <br />These tests indicated that the toxicity was due primarily to the high salt con• <br />tent of the water and tailings. <br />Supplementary tests were made to determine which salts or organic <br />reagents in the copper mill tailings solutions most affected plant growth. <br />The tailings water was compared with a prepared solution simulating saline but <br /> <br />