Lime Source Comparison Study for Reclamation of Sediments.

Excavated lake sediments (>16 inches thick) were used as cover materials during reclamation of mine sites in Montana.  Initial revegetation efforts failed due to inhibition of plant root elongation by elevated concentrations of water soluble Zn.  The objective of this research was to compare the effectiveness of various liming materials for increasing sediment pH and decreasing soluble Zn concentrations. Five random bulk samples of lake sediment were collected from a stockpile for soil analysis and greenhouse studies.  Saturated paste pH ranged from 4.40 to 6.99 with a corresponding range in soluble Zn (saturated paste extract) from 203 to 3 mg/L. An initial lime rate study was conducted using dolomitic lime, but the amendment failed to increase soil pH and decrease soluble Zn concentrations to non-inhibitory levels.  A subsequent study was conducted using an acidic lake sediment (pH= 4.4) to compare the effectiveness of the original dolomitic lime to pure calcium carbonate, hydrated lime (HL), lime kiln dust (LKD), and sugar beat lime (SBL).  All liming amendments were used at rates of 10 and 20 g/kg. Barley growth was used to quantify plant shoot and root response to each liming amendment.  Based on above and below growth, LKD and SBL were equally effective at reducing the inhibitory effects of soluble Zn followed closely by pure calcium carbonate.  Hydrated lime was effective at the low rate but was detrimental to plant growth at the high rate due to initially high pH values.  Dolomitic lime was least effective due to low reactivity of the material.