Effect of Manure Application on Net Nitrification Rates, Heavy Metal Concentrations and Nitrifying Archaea/Bacteria in Soils.

In this study, we determined the effect of manure application on net nitrification rates (NNRs), heavy metal concentrations (HMCs), and abundance of ammonia-oxidizing archaea (AOA)/bacteria (AOB), and nitrite-oxidizing bacteria (NOB) in soil. HMCs were measured by atomic absorption spectroscopy. Abundance of AOA, AOB, and NOB was enumerated by q-PCR. NNRs ranged from 2.8 to 14.7 mg kg-1 h-1 and were significantly (p < 0.05) increased in manure soils as compared to control soils. NNRs were affected by pH 7 and temperature 30°C. Cd, Fe and Pb concentrations were classified as excessively polluted, moderate contamination and slight pollution, respectively, in the manure soils. NNRs and concentrations of Fe and Pb were significantly (p < 0.00) positive correlated, but Cu and Cd were significantly (p < 0.00) negative correlated with NNRs. Application of manure significantly (p < 0.05) increased HMCs (Fe, Cu, and Pb), which have indirect and direct effects on NNRs and nitrifying bacteria.