Contribution of nitrification and denitrification to nitrous oxide emissions from soils after application of biogas waste and other fertilizers

Abstract

The attribution of nitrous oxide (N(2)O) emission to organic and inorganic N fertilizers requires understanding of how these inputs affect the two biological processes, i.e. denitrification and nitrification. Contradictory findings have been reported when the effects of organic and inorganic fertilizers on nitrous oxide emission were compared. Here we aimed to contribute to the understanding of such variation using (15)N-labelling techniques. We determined the processes producing N(2)O, and tested the effects of soil moisture, N rates, and the availability of organic matter. In a pot experiment, we compared soil treated with biogas waste (BGW) and mineral ammonium sulphate (Min-N) applied at four rates under two soil moisture regimes. We also tested biogas waste, conventional cattle slurry and mineral N fertilizer in a grassland field experiment. During the first 37 days after application we observed N(2)O emissions of 5.6 kg N(2)O-N ha(-1) from soils supplied with biogas waste at a rate of 360 kg N ha(-1). Fluxes were ca. 5-fold higher at 85% than at 65% water holding capacity (WHC). The effects of fertilizer types and N rates on N(2)O emission were significant only when the soil moisture was high. Organic fertilizer treated soils showed much higher N(2)O emissions than those receiving mineral fertilizer in both, pot and field experiment. Over all the treatments the percentage of the applied N emitted as N(2)O was 2.56% in BGW but only 0.68% in Min-N. In the pot experiment isotope labelling indicated that 65-95% of the N(2)O was derived from denitrification for all fertilizer types. However, the ratio of denitrification/nitrification derived N(2)O was lower at 65% than at 85% WHC. We speculate that the application of organic matter in conjunction with ammonium nitrogen first leads to a decrease in denitrification-derived N(2)O emission compared with soil receiving mineral fertilizer. However, at later stages when denitrification becomes C-limited, higher N(2)O emissions are induced when the soil moisture is high.

Short-term effects of biogas digestate and cattle slurry application on greenhouse gas emissions affected by N availability from grasslands on drained fen peatlands and associated organic soils

“…Higher N 2 O emissions derived from biogas digestates were also reported by a few other authors (e.g. Senbayram et al, 2009;Sänger et al, 2010), whereas Clemens et al (2006) found no differences between untreated and digested slurry.…”

“…Since digested products are more recalcitrant than fresh slurry it could be assumed that microbial degradation is slow, resulting in fewer anoxic microsites and reduced N 2 O emissions compared with fresh slurry application (Clemens and Huschka, 2001;Oenema et al, 2005;Möller and Stinner, 2009). However, the few available field and laboratory experiments are contradictory regarding the effect of biogas digestate application on N 2 O emissions (e.g., Clemens and Huschka, 2001;Wulf et al, 2002b;Clemens et al, 2006;Senbayram et al, 2009;Sänger et al, 2010), and very few studies exist for grasslands (e.g., Wulf et al, 2002b, Clemens et al, 2006.…”

“…Methane acts as a strong GHG, whereas NH 3 is considered an indirect GHG through ammonia deposition which could promote the formation of N 2 O (Moiser, 2001). Moreover, NH 3 deposition causes soil acidification and eutrophication of ecosystems (e.g., Fangmeier et al, 1994;Galloway, 1995Galloway, , 2001Smith et al, 1999). In Germany, agriculture is responsible for 95.3 % of anthropogenic NH 3 emissions (Haenel et al, 2010).…”

Ammonia oxidation pathways and nitrifier denitrification are significant sources of N 2 O and NO under low oxygen availability

“…Many field experiments have shown that the bulk of seasonal N 2 O emissions occurs shortly after fertilizer N applications (36,37) when N 2 O production through the NH 3 oxidation pathways is most likely because almost all synthetic N fertilizers supply N in the ammonical form. Our results support those of recent analyses of global trends of the N 2 O molecule's 15 N, 18 O, and site preference (δ 15 N α -δ 15 N β ) signature that point to the contribution of ammonical N fertilizers and possibly nitrification as the principal sources responsible for the rise in atmospheric N 2 O (38).…”

“…The extracted soils were centrifuged at 13,000 × g for 20 seconds and the supernatant was frozen at −20°C. Isotope analysis of soil mineral N was performed on aliquots of the extracts using a diffusion technique (49 (36). Then, the contribution of the different NH 3 oxidation pathways (NN, ND, and NCD) to N 2 O production was calculated based on the combined 18 O and 15 N data according to the dual-isotope method of Kool et al (29,31).…”