of clay, silt, and sand calculated (Whiting et al., 2003). Soil texture
was then determined using the soil texture triangle (McDonald,
1984). Soil stability was determined based on the Emerson
Dispersion Test where the breakdown of aggregates in water
assigns the substrate material into different classes of stability:
Class 1 – very unstable, Class 2 – partly stable, Class 3 – stable,
and Class 4 – very stable. The organic matter content was determined
by dry-ashing the substrate material in a muffle furnace
at 440 C and recording the following masses: dry soil, ashed soil,
organic matter (dry soil – ashed soil). The percentage organic matter
was calculated as: OM = (organic matter/dry soil) ⁄ 100.
The growth substrates consisted of a mixture of biosolids and
mine tailings (v/v %): 0% biosolids-100% mine tailings (0% BS);
10% biosolids-90% mine tailings (10% BS); 25% biosolids-75% mine
tailings (25% BS); 50% biosolids-50% mine tailings (50% BS); 75%
biosolids-25% mine tailings (75% BS); and 100% biosolids-0% mine
tailings (100% BS). A seed raising mix and garden potting mix
served as the control growth substrates.