Abstract
Peatlands drained for agriculture emit large amounts of nitrous oxide (N2O) and thereby contribute to global warming. In order to counteract soil subsidence and sustain agricultural productivity, mineral soil coverage of drained organic soil is an increasingly used practice. This management option may also influence soil-borne N2O emissions. Understanding the effect of mineral soil coverage on N2O emissions from agricultural peatland is necessary to implement peatland management strategies which not only sustain agricultural productivity but also reduce N2O emissions. In this study, we aimed to quantify the N2O emissions from an agriculturally managed peatland in Switzerland and to evaluate the effect of mineral soil coverage on these emissions. The study was conducted over two years on a grassland on drained nutrient-rich fen in the Swiss Rhine Valley which was divided into two parts, both with identical management. One site was not covered with mineral soil (reference “Ref”), and the other site had a ∼40 cm thick mineral soil cover (coverage “Cov”). The grassland was intensively managed, cut 5–6 times per year, and received c. 230 kg N ha−1 yr−1 of nitrogen fertilizer. N2O emissions were continuously monitored using an automatic time integrating chamber (ATIC) system. During the experimental period, site Ref released 20.5 ± 2.7 kg N ha−1 yr−1 N2O-N, whereas the N2O emission from site Cov was only 2.3 ± 0.4 kg N ha−1 yr−1. Peak N2O emissions were mostly detected following fertilizer application and lasted for 2–3 weeks before returning to the background N2O emissions. At both sites, N2O peaks related to fertilization events contributed more than half of the overall N2O emissions. However, not only the fertilization induced N2O peaks but also background N2O emissions were lower with mineral soil coverage. Our data suggest a strong and continued reduction in N2O emissions with mineral soil cover from the investigated organic soil. Mineral soil coverage, therefore, seems to be a promising N2O mitigation option for intensively used drained organic soils when a sustained use of the drained peatland for intensive agricultural production is foreseen, and potential rewetting and restoration of the peatland are not possible.
Highlights
Nitrous oxide (N2O) is the third most important long-lived greenhouse gas (GHG) and an important reactant with stratospheric ozone (Ravishankara et al, 2009; Prather et al, 2015)
We found that 50 to 60% of the variation in fertilization induced N2O peaks (F-peak) N2O emissions could be explained by the multiple linear regression model with soil temperature, soil water-filled pore space, and amount of N input as explanatory variables (Table 3)
For some of the study sites mentioned by Tiemeyer et al (2016), where fertilizer input was higher than 300 kg N ha−1 yr−1, these authors reported higher N2O emissions of 6.4–27.2 kg N ha−1 yr−1
Summary
Nitrous oxide (N2O) is the third most important long-lived greenhouse gas (GHG) and an important reactant with stratospheric ozone (Ravishankara et al, 2009; Prather et al, 2015). Peatlands are an important pool of organic nitrogen (N) of 8–15 Gt N (Leifeld and Menichetti, 2018). Longterm drainage causes peatland subsidence due to physical processes and mineralization of the surface peat. These processes cause soil degradation and induce very high GHG emissions, which turned the global peatland biome from a net GHG sink to a net source. Peatland management strategies, which could sustain the productive use of organic soil and counterbalance soil subsidence and reduce N2O emission, are urgently needed. It changes the topsoil properties of drained organic soil and influences substrate availability for N2O production. The topsoil contains much less organic matter than the degrading peat. Carbon and nitrogen availability for denitrification might become limiting, thereby influencing
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