Dataset Information

Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils.

ABSTRACT: Biochar (BC) application to soil suppresses emission of nitrous- (N2O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N2O and N2) were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH) were also included in the study. The untreated BCs suppressed N2O and NO and increased N2 production during denitrification, irrespective of the effect on denitrification rate. The extent of N2O and NO suppression was dose-dependent and increased with the alkalizing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N2O and NO net production. Just like untreated BCs, NaOH reduced net production of N2O and NO while increasing that of N2. This confirms the importance of altered soil pH for denitrification product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH.

SUBMITTER: Obia A

PROVIDER: S-EPMC4580641 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils.

Obia Alfred A Cornelissen Gerard G Mulder Jan J Dörsch Peter P

PloS one 20150923 9

Biochar (BC) application to soil suppresses emission of nitrous- (N2O) and nitric oxide (NO), but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrific ...[more]

PMID: 26397367

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Project description:UnlabelledAccumulating empirical evidence over the last 60 years has shown that the reduction of N2O to N2 is impaired by low soil pH, suggesting that liming of acid soils may reduce N2O emissions. This option has not gained much momentum in global change research, however, possibly due to limited understanding of why low pH interferes with N2O reductase. We hypothesized that the reason is that denitrifying organisms in soils are unable to assemble functional N2O reductase (N2OR) at low pH, as shown to be the case for the model strain Paracoccus denitrificans. We tested this by experiments with bacteria extracted from soils by density gradient centrifugation. The soils were sampled from a long-term liming experiment (soil pH 4.0, 6.1, and 8.0). The cells were incubated (stirred batches, He atmosphere) at pH levels ranging from 5.7 to 7.6, while gas kinetics (NO, N2O, and N2) and abundances of relevant denitrification genes (nirS, nirK, and nosZ) and their transcripts were monitored. Cells from the most acidic soil (pH 4.0) were unable to reduce N2O at any pH. These results warrant a closer inspection of denitrification communities of very acidic soils. Cells from the neutral soils were unable to produce functional N2OR at pH values of ≤6.1, despite significant transcription of the nosZ gene. The N2OR expressed successfully at pH 7.0, however, was functional over the entire pH range tested (5.7 to 7.6). These observations lend strong support to our hypothesis: low soil pH diminishes/prevents reduction of N2O, primarily by precluding a successful assembly of functional N2O reductase.ImportanceImpaired N2O reduction in acid soils was first observed ~60 years ago, and the phenomenon has been rediscovered several times since then. The practical implication would be that the emissions of N2O from cropped soils could be controlled by soil pH management, but this option has largely been ignored till now. One reason for this could be that the mechanisms involved have remained obscure. Here, we provide compelling evidence that the primary reason is that low pH interferes with the making of the enzyme N2O reductase rather than the function of the enzyme if properly assembled. The implications are important for understanding how pH controls the kinetics of N2O and N2 production by denitrification. The improved understanding provides credibility for soil pH management as a way to mitigate N2O emissions.

Dataset Information

Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils.

Publications

Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils.

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