Contingent Effects of Liming on N2O-Emissions Driven by Autotrophic Nitrification

作者：Shahid Nadeem, Lars R. Bakken, Åsa Frostegård, John Christian Gaby, Peter Dörsch · 发表于：Frontiers in Environmental Science · 年份：2020 · DOI：10.3389/fenvs.2020.598513 · 被引用次数：55 · 研究领域：Soil Carbon and Nitrogen Dynamics、Soil and Unsaturated Flow、Clay minerals and soil interactions

Liming acidic soils is often found to reduce their N 2 O emission due to lowered N 2 O/(N 2 O + N 2 ) product ratio of denitrification. Some field experiments have shown the opposite effect, however, and the reason for this could be that liming stimulates nitrification-driven N 2 O production by enhancing nitrification rates, and by favoring ammonia oxidizing bacteria (AOB) over ammonia oxidizing archaea (AOA). AOB produce more N 2 O than AOA, and high nitrification rates induce transient/local hypoxia, thereby stimulating heterotrophic denitrification. To study these phenomena, we investigated nitrification and denitrification kinetics and the abundance of AOB and AOA in soils sampled from a field experiment 2–3 years after liming. The field trial compared traditional liming (carbonates) with powdered siliceous rocks. As expected, the N 2 O/(N 2 O + N 2 ) product ratio of heterotrophic denitrification declined with increasing pH, and the potential nitrification rate and its N 2 O yield ( Y N2O : N 2 O-N/NO 3 – -N), as measured in fully oxic soil slurries, increased with pH, and both correlated strongly with the AOB/AOA gene abundance ratio. Soil microcosm experiments were monitored for nitrification, its O 2 -consumption and N 2 O emissions, as induced by ammonium fertilization. Here we observed a conspicuous dependency on water filled pore space (WFPS): at 60 and 70% WFPS, Y N2O was 0.03-0.06% and 0.06–0.15%, respectively, increasing with increasing pH, as in the aerobic so...