Understanding the relative contributions of fungi and bacteria led nitrous oxide emissions in an acidic soil amended with industrial waste.

Amendment of fertilized arable soil with alkaline industrial waste has the potential to ameliorate soil acidification whilst also improving crop yield. Another co-benefit is nitrous oxide (N2O) emission abatement but the contribution of fungi and bacteria involved in this process remains unclear. Two incubation experiments were conducted to: 1) examine how amendment of acidic soils with a mixture of phosphorus tailings mixture and insoluble potassium-containing rocks (PT) affect N2O emissions and 2) understand the microbial mechanisms and relative contributions of fungi and bacteria responsible for N2O emissions. In the first incubation experiment, the four treatments consisted of: i) the study control, ii) urea, iii) PT amendment and iv) PT amendment plus urea. Results showed that the PT amendment significantly increased soil pH from 4.8 to above 6.0, and reduced N2O emissions by 65.7%. PT-amended soils had higher N2 emissions and faster O2 consumption. The PT amendment significantly increased extracellular enzyme activities of leucine aminopeptidase and N-Acetyl-β-glucosaminidase, while it significantly decreased activities of β-1, 4-glucosidase and β-cellobiosidase. Two antibiotics (cycloheximide and streptomycin) combined with substrate-induced respiration method were used in the second incubation experiment. Compared to soil with urea, urea with PT amendment raised soil bacteria-related N2O from 9.2% to 18.8% while decreasing fungi-related N2O from 50.5% to 43.2%. These findings suggest that the N2O emissions from acidic soils can be considerably mitigated by the application of alkaline industrial wastes. The contribution of fungi should be considered when designing and applying N2O mitigation strategies in acidic soils. DATA AVAILABILITY: Data will be made available on request.