Laserfiche WebLink
16 <br /> on other tailings. These opposing effects were deemed to depend principally <br /> on two factors : First, if salt-containing tailings produced an appreciable <br /> osmotic concentration when watered, the fertilizer appeared to increase this <br /> concentration with deleterious effect on the plants. Second, if heavy-metal- <br /> containing minerals were solubilized by the ammonia in the fertilizer, the <br /> metal ions hindered plant growth. <br /> Overcoming Salinity and Acidity Problems <br /> Research was conducted to devise means of overcoming the deleterious <br /> effects of salts and acids in mill tailings. The following three methods were <br /> considered: (1) Percolation leaching of the salts from the tailings; <br /> (2) stratification of the sand and slime fractions of the tailings during <br /> deposition; and (3) solar orientation of mounds of tailings to produce differ- <br /> ential concentrations of salt on shaded and sunlit sides of the mound. <br /> Additional research for overcoming salinity problems only is underway, <br /> encompassing the addition of sulfur in various forms to saline soil and tail- <br /> ing materials. Native and byproduct gypsum, sulfur, sulfur plus limestone, <br /> pyrite, ferrites , and sulfuric acid are under consideration as additives and <br /> test plots have been established. Insufficient time has elapsed to properly <br /> evaluate the results and the findings are not included in this report. <br /> A minimum of work was done on percolation leaching, because an apparently <br /> satisfactory means of leaching highly acidic tailings has been reported (D. <br /> The work by James showed flooding is not an effective means of leaching acid- <br /> ity from tailings because (1) prolonged flooding compacts the materials pro- <br /> ducing conditions unfavorable for plant growth, and (2) when flooding is <br /> halted, evaporation brings the acid to the surface again. James' investiga- <br /> tions indicated that the downward movement of acidity can be encouraged by an <br /> extremely fine spray of water which forms a mist over the surface and retards <br /> evaporation. If the spray of water applied does not exceed the rate at which <br /> it can penetrate the tailings, high acidity can be moved to a sufficient depth <br /> to permit vegetative growth within a period of 3 to 4 weeks. If the acid can <br /> be moved downward to contact a slime layer with which it reacts, subsequent <br /> evaporative movement will not return the acid to the surface. <br /> These projections have recently been substantiated by research on the <br /> reclamation of saline soils using drip irrigation and widely spaced deep <br /> furrows in planting. Practitioners of drip irrigation indicate that spot <br /> irrigation with small amounts of water sufficient to drive the majority of the <br /> salts beyond the pickup zone of the plant roots speeds vegetative growth. Sim <br /> ilarly, good vegetative growth of grasses and legumes in harsh saline environ- <br /> ments has been achieved by planting the seeds in 4- to 6-inch-deep furrows <br /> spaced at intervals from 12 to 42 inches apart. The wide spacing between <br /> furrows reduces plant competition and the deepness of the furrow permits con- <br /> centration of the water and directs the salts to the ridges between furrows. <br /> Other studies made by the Bureau indicated that stratification and mound- <br /> ing of tailings were effective in ameliorating salinity problems. Comparative <br /> vegetative growth tests were made (1) in unstratified plots of tailings <br />