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

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 ÿ1 soil or 210 kg dry sludge ha ÿ1 or left unamended. Amended and unamended soils were incubated aerobically for 70 days at 22 2°C and CO2 production, available P, and inorganic N concentrations were monitored. The CO2 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 ÿ1 soil could not be accounted for in the ®rst days of the incubation. Nitri®cation showed a lag, which lasted 28 days, and concentration of available P remained constant or increased slightly. Application of tannery sludge to soil increased CO2 production with 6.5 mg CO2 kg ÿ1 soil d ÿ1 and inorganic N with 30 mg N kg ÿ1 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 e€ects on the biological functioning of the soil were found, further investigation into possible long-term environmental e€ects are necessary.