Effects of biochar application on soil greenhouse gas fluxes: a meta‐analysis

Yanghui He,Xuhui Zhou,Guiyao Zhou,Xihua Wang,Ming Li,Liling Jiang,Shahla Hosseini Bai,Junjiong Shao,Zhenggang Du,Chengyuan Xu,Helen Wallace,Zhihong Xu

doi:10.1111/gcbb.12376

Abstract

AbstractBiochar application to soils may increase carbon (C) sequestration due to the inputs of recalcitrant organic C. However, the effects of biochar application on the soil greenhouse gas (GHG) fluxes appear variable among many case studies; therefore, the efficacy of biochar as a carbon sequestration agent for climate change mitigation remains uncertain. We performed a meta‐analysis of 91 published papers with 552 paired comparisons to obtain a central tendency of three main GHG fluxes (i.e., CO2, CH4, and N2O) in response to biochar application. Our results showed that biochar application significantly increased soil CO2 fluxes by 22.14%, but decreased N2O fluxes by 30.92% and did not affect CH4 fluxes. As a consequence, biochar application may significantly contribute to an increased global warming potential (GWP) of total soil GHG fluxes due to the large stimulation of CO2 fluxes. However, soil CO2 fluxes were suppressed when biochar was added to fertilized soils, indicating that biochar application is unlikely to stimulate CO2 fluxes in the agriculture sector, in which N fertilizer inputs are common. Responses of soil GHG fluxes mainly varied with biochar feedstock source and soil texture and the pyrolysis temperature of biochar. Soil and biochar pH, biochar applied rate, and latitude also influence soil GHG fluxes, but to a more limited extent. Our findings provide a scientific basis for developing more rational strategies toward widespread adoption of biochar as a soil amendment for climate change mitigation.

Highlights

The global average surface temperature has increased by 0.85 °C over the period 1880–2012 based on multiple independently produced datasets, and current projections suggest that the temperature is likely to increase by another 0.3–4.8 °C by the end of this century (IPCC, 2013)
We compiled data from individual experimental studies that quantified the effect of soil biochar application on greenhouse gas (GHG) fluxes across various ecosystems and quantitatively evaluated the responses of soil CO2, CH4, and N2O fluxes to biochar application under different environmental and experimental conditions using meta-analysis techniques
The responses of soil N2O fluxes to biochar application revealed negative trends with soil pH (P = 0.001) and application rate (P < 0.001)

Summary

Introduction

The global average surface temperature has increased by 0.85 °C over the period 1880–2012 based on multiple independently produced datasets, and current projections suggest that the temperature is likely to increase by another 0.3–4.8 °C by the end of this century (IPCC, 2013). Greenhouse gas mitigation strategies include reducing and avoiding emissions as well as enhancing the A field trial in paddy soils amended with biochar produced from wheat straw induced a 12% increase in CO2 emissions, but a 41.8% decrease in N2O emissions (Zhang et al, 2012b). Another field experiment in pasture showed no significant effects of biochar amendment on soil CO2 and N2O emissions in a pasture ecosystem (Scheer et al, 2011). The efficacy of biochar for climate change mitigation is largely uncertain due to these variable effects on soil GHG emissions

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