Thiocyanate increases the nitrous oxide formation process through modifying the soil bacterial community

BACKGROUND Nitrous oxide (N2 O) is a potent greenhouse gas depleting the stratospheric ozone. Previous studies reported that the thiocyanate (TC) excretion in the urine of cattle fed rapeseed meals containing glucosinolates was positively correlated with the N2 O-nitrogen (N) emissions. The objectives of the experiment were to verify the effects and the mechanism of TC on the N2 O-N emissions from the soil applied with artificial urine using static incubation technique. Four levels of TC, that is 0.00, 0.26, 0.78 and 2.33 mmol L-1 were composited in artificial urine as experimental treatments. Soil inorganic N and bacterial community were analyzed to elucidate the effects of TC on the N2 O-N emissions of artificial urine. RESULTS Adding TC increased the N2 O-N fluxes, the N2 O-N to N application ratio, and the estimated N2 O-N emissions from the soil applied with artificial urine both linearly and quadratically. The estimated N2 O-N emission (Y, in μmol) was increased with the TC adding level (X, in μmol) in a quadratic manner: Y=52.57+4.47X-0.123X2 (R 2 = 0.70). Adding TC did not affect the soil bacterial diversity and richness, but increased the relative abundances of Nitrosomonas (both for nitrification and denitrification) and Hyphomicrobium, Lysobacter and Terrimonas (for denitrification), and tended to increase the relative abundances of denitrification and dissimilatory nitrate reduction to ammonium. CONCLUSION TC increased the N2 O-N emissions of the soil applied with artificial urine possibly through enhancing the denitrification of nitrifiers in the soil. Field experiments are necessary to verify the laboratory results. © 2021 Society of Chemical Industry.