Developing manufactured soils from industrial by-products for use as growth substrates in mine reclamation

Suitable soils for reclamation can be acquired through excavation and translocation of local soils, increasing the industrial footprint on previously undisturbed lands and causing negative environmental impacts. Manufactured soils (Technosols) could be a viable soil source when the availability of suitable natural soils is limited. The purpose of this study was to manufacture a Technosol from an admixture of woody residuals, primary paper sludge, and two subtypes of nonacid generating crushed mine rock, to function as a growth substrate for revegetation of mined land. Technosols manufactured with 0, 25, 50, and 75% organic materials (v/v) were assessed in a 10-week growth study using annual ryegrass biomass production and allocation as a performance indicator. Technosols containing no organic materials had significantly lower plant nutrient concentrations than Technosols containing an organic constituent and, after 5 weeks of growth, ryegrass grown on nonorganic Technosols had greater root:shoot ratios than ryegrass grown on organic Technosols. Organics increase the water holding capacity and nutrient concentrations of Technosols and should be included in manufacturing Technosols for revegetation. Technosols manufactured with primary paper sludge produced lower shoot biomass than Technosols manufactured with woody residuals, which could be in part due to the higher pH of the paper sludge. Technosols can be manufactured for revegetation purposes and individual components should be assessed before and after mixing. Further development of Technosols should include field testing and amendment or fertilizer use to improve soil nutrient content.