Effectiveness of pig sludge as organic amendment of different textural class mine tailings with different periods of amendment-contact time

© 2018 Elsevier Ltd The present study assesses the effect of tailing texture (loamy sand (LT) and sandy loam (ST)), dose of pig sludge (0, 50, 100 and 200 t ha¿1) and amendment-contact time (14, 28 and 42 days) on physicochemical quality of amended substrate using Lolium perenne var Nui as a bioindicator. The main properties of LT differed of ST in levels of total organic carbon (0.19 and 0.58%), in pH (4.6 and 8.5), total Cu (202 and 1647 mg kg¿1) and Zn content (31 and 137 mg kg¿1). Soil pore water of experimental substrates was characterized for pH, electrical conductivity (EC) and Cu2+ ion activity (pCu2+) while ammonium nitrogen (NH4 +-N), infiltration rate and general physicochemical characteristics were measured in substrates. Shoot biomass (SB), root biomass (RB) and the RB:SB ratio was calculated for L. perenne. The results showed there to be a significant interaction (p < 0.05) between tailing texture, sludge dose and amendment-contact time for pCu2+, infiltration rate, SB, RB, and RB: SB ratio, but not for pH, EC, or NH4 +-N. However, sludge dose and amendment-contact time significantly affected all variables. By increasing dosages of pig sludge, pore water pH increased, and this was associated with decreases in pCu2+ and the infiltration rate. High doses of pig sludge (100 and 200 t ha¿1) impaired growth of L. perenne irrespective of tailing texture and amendment-contact time, likely because of the rise of EC (up to 14 mS cm¿1). For both tailing textures, the highest biomass was obtained after incorporation of 50 t ha¿1 of pig sludge, with increasing values as amendment-contact time rose. In conclusion, effective management of pig sludge for tailing reclamation should guarantee doses <50 t ha¿1 and amendment-contact time >28 days, irrespective of tailing texture.