Effects of Biochar Addition on Greenhouse Gas Emissions and Microbial Responses in a Short-Term Laboratory Experiment

Abstract

Biochar application to soil has drawn much attention as a strategy to sequester atmospheric carbon in soil ecosystems. The applicability of this strategy as a climate change mitigation option is limited by our understanding of the mechanisms responsible for the observed changes in greenhouse gas emissions from soils, microbial responses, and soil fertility changes. We conducted an 8-wk laboratory incubation using soils from PASTURE (silt loam) and RICE PADDY (silt loam) sites with and without two types of biochar (biochar from swine manure [CHAR-M] and from barley stover [CHAR-B]). Responses to addition of the different biochars varied with the soil source. Addition of CHAR-B did not change CO and CH evolution from the PASTURE or the RICE PADDY soils, but there was a decrease in NO emissions from the PASTURE soil. The effects of CHAR-M addition on greenhouse gas emissions were different for the soils. The most substantial change was an increase in NO emissions from the RICE PADDY soil. This result was attributed to a combination of abundant denitrifiers in this soil and increased net nitrogen mineralization. Soil phosphatase and N-acetylglucosaminidase activity in the CHAR-B-treated soils was enhanced compared with the controls for both soils. Fungal biomass was higher in the CHAR-B-treated RICE PADDY soil. From our results, we suggest CHAR-B to be an appropriate amendment for the PASTURE and RICE PADDY soils because it provides increased nitrogen availability and microbial activity with no net increase in greenhouse gas emissions. Application of CHAR-M to RICE PADDY soils could result in excess nitrogen availability, which may increase NO emissions and possible NO leaching problems. Thus, this study confirms that the ability of environmentally sound biochar additions to sequester carbon in soils depends on the characteristics of the receiving soil as well as the nature of the biochar.

Combined effects of nitrogen deposition and biochar application on emissions of N2O, CO2and NH3from agricultural and forest soils

“…Concurrently, the CO 2 emissions from agricultural soil also increased with biochar addition during the first N deposition event (Fig. 1c), which is consistent with the results of Yoo and Kang (2012). These findings can be partly explained by the following facts: right after the incorporation of biochar into soils, volatile biochar compounds (aliphatic compounds) may act as decomposable organic C sources in soil and thus provide a readily available substrate for denitrifying microorganisms (Blagodatskaya and Kuzyakov 2008;Ameloot et al 2013); due to the priming effect (soil microbial community has been stimulated due to the addition of various organic amendments), biochar incorporation with a high C/N ratio may stimulate soil microorganisms to decompose SOM (Kuzyakov et al 2000;Bünemann et al 2006;Smith et al 2010;Nelissen et al 2012).…”

A Review of Biochar and Soil Nitrogen Dynamics

“…Anderson et al [75] concluded that adding biochar to the soil potentially increased microbial N cycling, especially the abundance of those organisms that may decrease N 2 O fluxes and NH 4 + concentrations. Conversely, Yoo and Kang [61] suggested the higher N 2 O fluxes observed in the presence of swine manure-derived biochar in paddy soils was partially a consequence of higher denitrifier abundance.…”

“…To date, several studies have shown that the addition of biochar to soils can mitigate N 2 O emissions in situ from soybean and grass ecosystems [48], following ruminant urine deposition [49], in wheat plots [50] and during laboratory or greenhouse incubations under various conditions [8,9,47,[51][52][53][54][55][56][57][58][59][60][61] while other studies have found no differences or even increases in cumulative N 2 O emissions after biochar addition [61][62][63].…”

“…Similarly, every opportunity should be taken to assess changes in microbial community form and function to elucidate biochar effects on N 2 O emissions. For example, Yoo and Kang [61] attributed an increase in N 2 O emissions, after biochar application, in a rice paddy field to abundant pre-existing denitrifiers.…”

Pyrolysis Dynamics of Biomass Residues in Hot-Stage

“…Biochar ash content, pyrolysis conditions, and C/N ratios seem to be key factors influencing N2O emissions, while a direct correlation has been found between biochar application rate and N2O emission mitigation (Liu et al 2012;Cayuela et al 2014). The ability of environmentally sound biochar to sequester carbon in soils depends on the characteristics of the receiving soil, as well as the structure and composition of the biochar (Lehmann et al 2011;Yoo and Kang 2012). Biochars, in comparison to composts, tend to sequester C, yet a combination of both might be desirable for sustaining long-term fertility of soils (Bolan et al 2012).…”