Lime requirement and availability of nutrients and toxic metals to plants grown in acid mine tailings

Six acid pyrite-bearing mine tailings samples, varying in pH from 1.9 to 2.9, yielded from 10.8 to 37.0 meq acid/100-g sample when leached with 1 liter H 2 O. In pot tests, the amounts of CaCO 3 required to neutralize the initial acidity and that generated during cropping in four of the samples containing less than 5% S varied from 10,000 to 50,000 ppm. The acidity of the other two samples, which contained considerably more S, was corrected by liming initially, but the pH was less than 2.5 by the end of the cropping period despite high additions of CaCO 3 (100,000, and 140,000 ppm). Reed canary grass was grown successfully in the limed and fertilized tailings except in an unweathered sample containing a relatively high amount of S. In most instances, the composition of the plants did not vary greatly from that reported for plants grown in soil, although the concentrations of S tended to be high. In this and another experiment with buckwheat, a soil layer on top of the tailings was used with varying effectiveness in establishing vegetation. With inadequate lime, the soil became very acid and released relatively high amounts of Mn, Fe and Al to the plants. Recovery of added K by extraction with 0.1 N acetic acid decreased with increasing acidity of the tailings.