Effect of pH on the denitrifying enzyme activity in pasture soils in relation to the intrinsic differences in denitrifier communities

Abstract

The effects of pH on denitrifying enzyme activity (DEA) and on the ratio of the denitrification products, N(2)O and N(2), were determined in three pasture soils differing in cattle impact. The linkage between intrinsic differences in the denitrifying communities and pH effects on relative N(2)O production was also assessed. Soil pH values were adjusted just before DEA determination to obtain soil slurries with a range of pH values. The intrinsic differences in the denitrifier communities were assessed by measuring the kinetic constants of NO(3)(-) and N(2)O reductions. DEA for all three soils was highest at pH 8.4, regardless of native soil pH. Because DEA has typically been measured at native soil pH, our results suggest that DEA might have been underestimated in many previous studies. Further, relative N(2)O production at different pH values did not differ among the soils, even though the denitrifier communities differed in their intrinsic capability to reduce NO(3)(-) all the way to N(2), suggesting that the ratio of denitrification products (N(2)O and N(2)) is pH-specific rather than soil-specific. This suggests that manipulations of soil pH will alter N(2)O fluxes from agricultural soils.

Management of soil pH promotes nitrous oxide reduction and thus mitigates soil emissions of this greenhouse gas

“…This is in agreement with the results obtained by ref. 29 , which can be summarized as “the ratio of denitrification products is pH-specific rather than soil-specific”. Consistencies between our results and the literature 22–24 suggest that the functions proposed are valid not only in France but perhaps also in different parts of the world (e.g., China).…”

Stimulation of NO and N2O emissions from soils by SO2 deposition

“…Manconi et al (2006b) reported that sulfide influenced the production and consumption of intermediate N 2 O during reduction of Fe(II)EDTA 2À bound NO, but sulfate and sulfite do not affect the reduction rate under the incubation conditions of pH 7.2 at 55°C. It has been well documented that the ratios of N 2 O to produced NO 3 À during the nitrification process and to N 2 during the denitrification process increase with decreasing soil pH (Mørkved et al, 2007;Cuhel & Simek, 2011;Zhang et al, 2011a). Thus, soil acidification, as a consequence of sulfite oxidation and acidity of ammonium sulfate, would be responsible for the stimulatory effects on N 2 O emissions from rice fields and some types of humid subtropical soils treated with ammonium sulfate (Cai et al, 1997;), as well as NO emissions from a coniferous forest soil with acidic irrigation (Papke & Papen, 1998).…”

Variation in the nitrous oxide reductase gene (nosZ)-denitrifying bacterial community in different primary succession stages in the Hailuogou Glacier retreat area, China

“…Environmental factors can significantly affect both the denitrification process and the functional genes involved in this microbially mediated pathway, and factors such as carbon substrate availability, moisture, pH, and other edaphic nutrients play crucial roles (Wallenstein et al, 2006). A previous study has shown that organic carbon is the limiting factor in microbial processes and activities in the early successional stages without vegetation cover, and carbon accumulation affects the availability of soil nitrogen (Wardle et al, 2004), in this sense, soil organic carbon and nitrogen levels in retreating glaciers can become the main driving factor in shaping the composition of nitrogen-related microbial communities, and soil pH is the most important factor impacting denitrification processes (Zeng et al, 2016;Čuhel et al, 2011 ;Kim et al, 2015). Jha et al (2017) have pointed out that the nosZ gene community structure had the strongest correlation with soil moisture content and available phosphorus.…”