High soil temperatures alter the rates of nitrification, denitrification and associated N2O emissions
The responses of nitrification and denitrification are not well characterised at temperatures above 35 °C, which is the focus of our study.
Materials and methods
Soils collected from two dairy pastures (Victoria, Australia) were incubated at 10 to 45 °C in the dark for 5 to 10 days following amendment with 100 μg N g−1 either as NH4NO3, 14NH415NO3 or 15NH415NO3 (10 atom% 15N excess) at 50% water-filled pore space. To detect N2O from heterotrophic nitrification, acetylene (0.01% v/v) was used in a subset of samples amended with 15NH415NO3. Atom% 15N enrichments of NO3ˉ, N2O and N2 were measured during the experiment to evaluate the responses of nitrification and denitrification to temperature.
Results and discussion
N2O production from the two soils increased with rising temperature and peaked between 35 and 40 °C. N2O production from nitrification and denitrification both had similar thermal responses, which were different to N2 production. The N2O/N2 ratio decreased from > 4 at 35–40 °C to 0.5 at 45 °C, due to greater N2 than N2O production in the Dermosol. Heterotrophic nitrifiers oxidised NH4+ and released N2O at 35–40 °C, suggesting a role for heterotrophs in N cycling under warm climates. Topt for nitrification was between 35 and 40 °C, which is higher than reported previously. A short-term effect of high temperatures could provide NH4+ for the growth of crops but may also decrease soil C pools.
Increasing temperature above 35 °C altered the rates of nitrification, denitrification associated N2O and N2 production. Nitrification and denitrification peaked at 35–40 °C in the Chromosol and Dermosol. The production of N2 increased rapidly above 40 °C, which may be related to high soil respiration rates that likely decreased O2 availability, thus expanding the anaerobic microsites; such circumstances increased the reduction of N2O to N2 production from the Dermosol.
KeywordsC pools Heterotrophs N2O reduction N2O/N2 ratios
This study was assisted through funding from the Vietnam International Education Development (VIED), The University of Adelaide and Tim Healy Memorial Scholarship (Future Farm Industries CRC). We acknowledge the assistance of Murray Unkovich (University of Adelaide), Nanthi Bolan (University of Newcastle) in assistance with methods, Kevin Kelly (Department of Economic Development, VIC, Australia) in providing site access for soil collection and environmental data, Nigel Charman for assistance with soil sampling and Ann McNeill and Nang Nguyen for technical assistance with mineral nitrogen analysis and soil physical measurements.
- Conant RT, Ryan MG, Ågren GI, Birge HE, Davidson EA, Eliasson PE, Evans SE, Frey SD, Giardina CP, Hopkins FM, Hyvönen R, Kirschbaum MUF, Lavallee JM, Leifeld J, Parton WJ, Megan Steinweg J, Wallenstein MD, Martin Wetterstedt JÅ, Bradford MA (2011) Temperature and soil organic matter decomposition rates–synthesis of current knowledge and a way forward. Glob Chang Biol 17:3392–3404CrossRefGoogle Scholar
- Crutzen P (1983) Atmospheric interactions. Homogeneous gas reactions of C, N, and S containing compounds. In: Bolin B, Cook R (eds) The major biogeochemical cycles and their interactions, vol SCOPE 21. Wiley, pp 67–114Google Scholar
- Davidson EA (1991) Fluxes of nitrous oxide and nitric oxide from terrestrial ecosystems. In: Rogers JE, Whitman BW (eds) Microbial production and consumption of greenhouse gases: methane, nitrogen oxides and halomethanes. Am. Soc. Microbiol, Washington, DC, pp 219–235Google Scholar
- Global Temperature (2018). In: Global Climate Change. NASA. Available via https://climate.nasa.gov/Global Temperature. Accessed 15 April 2018
- Gomez KA, Gomez AA (1984) Statistical procedures for agricultural research. Wiley, HobokenGoogle Scholar
- Haynes R (1986) Niitrification. In: Haynes R (ed) Mineral nitrogen in the plant-soil system. Academic, London, pp 127–165Google Scholar
- Isbell R (1996) The Australian soil classification. In: Australian soil and land survey handbook, vol 4. CSIRO, MelbourneGoogle Scholar
- Jones L, Peters B, Lezama J, Casciotti K, Fendorf S (2013) Emission of the greenhouse gas nitrous oxide resulting from ferrous iron disturbance of denitrification. In: AGU Fall Meeting Abstracts, p 0413Google Scholar
- Kaplan A (1965) Standard methods of clinical chemistry. Academic, New YorkGoogle Scholar
- Klemedtsson L, Svensson B, Rosswall T (1988) A method of selective inhibition to distinguish between nitrification and denitrification as sources of nitrous oxide in soil. Biol Fertil Soils 6:112–119Google Scholar
- Pierzynski GM, Vance GF, Sims JT (2005) Soils and environmental quality. CRC Press, Taylor & Francis GroupGoogle Scholar
- Sabey BR, Frederick LR, Bartholomew WV (1959) The formation of nitrate from ammounium in soils. III. Influence of temperature and initial population of nitrifying organisms on the maximum rate and delay period. Proc Soil Sci Soc Am 23Google Scholar
- Schimel JP, Firestone MK, Killham KS (1984) Identification of heterotrophic nitrification in a Sierran forest soil. Appl Environ Microbiol 48:802–806Google Scholar
- Schmidt EL (1982) Nitrification in soil. In: Stevenson F (ed) Nitrogen in agricultural soil, vol 22. American Soc. Agronomy, Madison, pp 253–267Google Scholar
- Tiedje JM (1988) Ecology of denitrification and dissimilatory nitrate reduction to ammonium. In: Zehnder AJB (ed) Environmental microbiology of anaerobes, vol 717. Wiley, New York, pp 179–244Google Scholar
- Tortoso AC, Hutchinson G (1990) Contributions of autotrophic and heterotrophic nitrifiers to soil NO and N2O emissions. Appl Environ Microbiol 56:1799–1805Google Scholar