Correlating denitrifying catabolic genes with N2O and N2 emissions from swine slurry composting

This work evaluated N dynamics that occurs over time within swine slurry composting piles. Real-time quantitative PCR (qPCR) analyzes were conducted to estimate concentrations of bacteria community harboring specific catabolic nitrifying-ammonium monooxygenase (amoA), and denitrifying nitrate- (narG), nitrite- (nirS and nirG), nitric oxide- (norB) and nitrous oxide reductases (nosZ) genes. NH3-N, N2O-N, N-2-N emissions represented 15.4 +/- 1.9%, 5.4 +/- 0.9%, and 79.1 +/- 2.0% of the total nitrogen losses, respectively. Among the genes tested, temporal distribution of narG, nirS, and nosZ concentration correlated significantly (p < 0.05) with the estimated N-2 emissions. Denitrifying catabolic gene ratio (cnorB + qnorB)/nosZ >= 100 was indicative of N2O emission potential from the compost pile. Considering our current empirical limitations to accurately measure N-2 emissions from swine slurry composting at field scale the use of these catabolic genes could represent a promising monitoring tool to aid minimize our uncertainties on biological N mass balances in these systems. (C) 2013 Elsevier Ltd. All rights reserved.