Nitrogen, carbon and phosphorus mineralization in soils from semi-arid highlands of central Mexico amended with tannery sludge

Abstract

Tannery sludge contains valuable nutrients and could be used as a fertilizer to pioneering vegetation in heavily eroded soils of the semi-arid highlands of central Mexico. Soil collected under and outside the canopy of mesquite ( Prosopis laeviginata), huizache ( Acacia tortuoso) and catclaw ( Mimosa biuncifera), and cultivated with maize ( Zea mays) and beans ( Phaesolus vulgaris) was amended with 1.5 g tannery sludge kg −1 soil or 210 kg dry sludge ha −1 or left unamended. Amended and unamended soils were incubated aerobically for 70 days at 22±2°C and CO 2 production, available P, and inorganic N concentrations were monitored. The CO 2 production rate, total C and P, available P, biomass C and P were larger under the canopy of the vegetation than outside of the canopy. The soils were depleted of N as more than 50 mg N kg −1 soil could not be accounted for in the first days of the incubation. Nitrification showed a lag, which lasted 28 days, and concentration of available P remained constant or increased slightly. Application of tannery sludge to soil increased CO 2 production with 6.5 mg CO 2 kg −1 soil d −1 and inorganic N with 30 mg N kg −1 soil after 70 days, but available P did not increase. Application of tannery sludge increased C and N mineralization and could thus provide valuable nutrients to a pioneer vegetation. Although no inhibitory effects on the biological functioning of the soil were found, further investigation into possible long-term environmental effects are necessary.