Applications of manure compost and sewage sludge resulted in a significant increase (p ⩽ 0.05) in the biomass of common reed when compared with those plants growing in pure tailings ( Fig. 3). Tailings that were amended with 5% manure compost (CuM5) or 10% sewage sludge (CuS10) were the most beneficial for the growth of common reed. In general, vetiver produced higher dry biomass than common reed in all treatments.
The results also indicated that the addition of NPK fertilizer (CuM5 + F and CuS5 + F) at the same amendment rates increased the biomass significantly (p ⩽ 0.05) in both vetiver and common reed, when compared with 5% organic wastes alone (CuM5 and CuS5). The root:shoot ratio of vetiver and common reed in Cu tailings was also reduced significantly (p ⩽ 0.05) after applications of manure compost and sewage sludge ( Fig. 4).