A laboratory study of soil conditions affecting emissions of nitrous oxide from packed cores subjected to freezing and thawing

• Published in: Canadian journal of soil science 2011-05, Vol.91 (2), p.223-233
• Main Authors: Tenuta, Mario, Sparling, Brad
• Format: Article
• Language: English
• Subjects: acetylene; Acetylene inhibition; bulk density; cold; denitrification; depth; dégel; dénitrification; Ecology, Biological Processes and Plant Interactions; emissions; enzyme activity; freezing; gel; Inhibition par l'acétylène; laboratory experimentation; masse volumique apparente; microbial biomass; N2O; nitrate; nitrates; nitrous oxide; organic matter; oxyde nitreux; profondeur; sandy loam soils; soil density; temperature; thaw; thawing
• ISSN: 0008-4271; 1918-1841
• DOI: 10.1139/CJSS09051

Tenuta, M. and Sparling, B. 2011. A laboratory study of soil conditions affecting emissions of nitrous oxide from packed cores subjected to freezing and thawing. Can. J. Soil Sci. 91: 223-233. A series of laboratory experiments using a packed core soil assay was carried out to test several soil conditions affecting the emission of N2O (nitrous oxide) during thawing of soil. The assay consisted of a sandy loam soil packed to 1.1 Mg m-3, moistened to 80% water-filled pore space, and temperature treated to 4 or -20°C for 2.5 d; the emissions from thawing soil were then determined as the differences in N2O release rates of the temperature-treated soils when placed at 15°C. Nitrate addition to surface soil (0-10 cm) enhanced thaw emission. Thaw emissions, averaged for deeper collected soil (10-30 and 30-60 cm), was 0.3% with NO3- treatment and 1.2% without NO3- treatment of that for surface soil treated similarly. Higher thaw emission for surface soil was related to greater organic matter and microbial biomass C contents and denitrifying enzyme activity than deeper collections of soil. Increasing the bulk density of soil from 1.1, 1.2, and 1.25 Mg m-3 decreased thaw emission. A second freeze-thaw cycle of the highest compaction treatment resulted in an emission of 2.3% of the first freeze-thaw cycle. Acetylene increased thaw emission of N2O and more so for NO3- untreated than treated soil. Using the acetylene inhibition method, the N2O:N2 ratio of gas produced was higher for frozen (0.17) than cold (0.07) treated soil, respectively, without the addition of NO3-. The addition of NO3- increased the N2O:N2 ratio of gas produced with the ratio being 2.45 and 0.53 for frozen and cold-treated soil. The results are consistent with biological denitrification being a source of N2O with conditions promoting N2O production rather than consumption enhancing thaw emissions.