Effects of biochar application on soil greenhouse gas fluxes: a meta-analysis
TL;DR: In this article, a meta-analysis of 91 published papers with 552 paired comparisons was performed to obtain a central tendency of three main GHG fluxes (i.e., CO2, CH4, and N2O) in response to biochar application.
Abstract: Biochar 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 gases (GHGs) 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 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 towards widespread adoption of biochar as a soil amendment for climate change mitigation; ;
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TL;DR: In this paper, the authors investigated the fate of BC applied to a savanna Oxisol in Colombia at rates of 0, 11.6, 23.2 and 116.1 t BC ha -1, as well as its effect on non-BC soil organic C.
Abstract: Black carbon (BC) is an important pool of the global C cycle, because it cycles much more slowly than others and may even be managed for C sequestration. Using stable isotope techniques, we investigated the fate of BC applied to a savanna Oxisol in Colombia at rates of 0, 11.6, 23.2 and 116.1 t BC ha -1 , as well as its effect on non-BC soil organic C. During the rainy seasons of 2005 and 2006, soil respiration was measured using soda lime traps, particulate and dissolved organic C (POC and DOC) moving by saturated flow was sampled continuously at 0.15 and 0.3 m, and soil was sampled to 2.0 m. Black C was found below the application depth of 0-0.1 m in the 0.15-0.3 m depth interval, with migration rates of 52.4 ± 14.5, 51.8 ± 18.5 and 378.7 ± 196.9 kg C ha -1 yr -1 (± SE) where 11.6, 23.2 and 116.1 t BC ha -1 , respectively, had been applied. Over 2 years after application, 2.2% of BC applied at 23.2 t BCha -1 was lost by respiration, and an even smaller fraction of 1% was mobilized by percolating water. Carbon from BC moved to a greater extent as DOC than POC. The largest flux of BC from the field (20-53% of applied BC) was not accounted for by our measurements and is assumed to have occurred by surface runoff during intense rain events. Black C caused a 189% increase in aboveground biomass production measured 5 months after application (2.4-4.5 additional dry biomass ha -1 where BC was applied), and this resulted in greater amounts of non-BC being respired, leached and found in soil for the duration of the experiment. These increases can be quantitatively explained by estimates of greater belowground net primary productivity with BC addition.
622 citations
TL;DR: Overall, diversification enhances biodiversity, pollination, pest control, nutrient cycling, soil fertility, and water regulation without compromising crop yields and shows promise to contribute to biodiversity conservation and food security from local to global scales.
Abstract: Enhancing biodiversity in cropping systems is suggested to promote ecosystem services, thereby reducing dependency on agronomic inputs while maintaining high crop yields. We assess the impact of several diversification practices in cropping systems on above- and belowground biodiversity and ecosystem services by reviewing 98 meta-analyses and performing a second-order meta-analysis based on 5160 original studies comprising 41,946 comparisons between diversified and simplified practices. Overall, diversification enhances biodiversity, pollination, pest control, nutrient cycling, soil fertility, and water regulation without compromising crop yields. Practices targeting aboveground biodiversity boosted pest control and water regulation, while those targeting belowground biodiversity enhanced nutrient cycling, soil fertility, and water regulation. Most often, diversification practices resulted in win-win support of services and crop yields. Variability in responses and occurrence of trade-offs highlight the context dependency of outcomes. Widespread adoption of diversification practices shows promise to contribute to biodiversity conservation and food security from local to global scales.
330 citations
TL;DR: In this paper, a review of the available literature on the effects of biochar on soil properties and GHG emissions in forest soils is presented, where the authors focus on the negative impacts of intensive forest management and global climate change on the quality of forest soils via soil acidification, reduction of soil organic carbon content, deterioration of soil biological properties, and reduction of the soil biodiversity.
Abstract: Forests play a critical role in terrestrial ecosystem carbon cycling and the mitigation of global climate change. Intensive forest management and global climate change have had negative impacts on the quality of forest soils via soil acidification, reduction of soil organic carbon content, deterioration of soil biological properties, and reduction of soil biodiversity. The role of biochar in improving soil properties and the mitigation of greenhouse gas (GHG) emissions has been extensively documented in agricultural soils, while the effect of biochar application on forest soils remains poorly understood. Here, we review and summarize the available literature on the effects of biochar on soil properties and GHG emissions in forest soils. This review focuses on (1) the effect of biochar application on soil physical, chemical, and microbial properties in forest ecosystems; (2) the effect of biochar application on soil GHG emissions in forest ecosystems; and (3) knowledge gaps concerning the effect of biochar application on biogeochemical and ecological processes in forest soils. Biochar application to forests generally increases soil porosity, soil moisture retention, and aggregate stability while reducing soil bulk density. In addition, it typically enhances soil chemical properties including pH, organic carbon stock, cation exchange capacity, and the concentration of available phosphorous and potassium. Further, biochar application alters microbial community structure in forest soils, while the increase of soil microbial biomass is only a short-term effect of biochar application. Biochar effects on GHG emissions have been shown to be variable as reflected in significantly decreasing soil N2O emissions, increasing soil CH4 uptake, and complex (negative, positive, or negligible) changes of soil CO2 emissions. Moreover, all of the aforementioned effects are biochar-, soil-, and plant-specific. The application of biochars to forest soils generally results in the improvement of soil physical, chemical, and microbial properties while also mitigating soil GHG emissions. Therefore, we propose that the application of biochar in forest soils has considerable advantages, and this is especially true for plantation soils with low fertility.
259 citations
TL;DR: It is indicated that biochar generally enhances soil P availability when added to soils alone or in combination with fertilizer, and provides a scientific basis for developing more rational strategies toward widespread adoption of biochar as a soil amendment for agricultural P and N management.
241 citations
Cooperative Research Centre1, University of Newcastle2, Foshan University3, University of New South Wales4, Tsinghua University5, University of Wollongong6, Nanjing Agricultural University7, Sejong University8, Hanyang University9, Kansas State University10, National University of Singapore11, Hong Kong Polytechnic University12, Korea University13, Sabaragamuwa University14, University of Wuppertal15, Kafrelsheikh University16, King Abdulaziz University17, Lancaster University18, University of Auckland19, University of Sri Jayewardenepura20, Egyptian Petroleum Research Institute21
TL;DR: Biochar is produced as a charred material with high surface area and abundant functional groups by pyrolysis, which refers to the process of thermochemical decomposition of organic material at elev...
Abstract: Biochar is produced as a charred material with high surface area and abundant functional groups by pyrolysis, which refers to the process of thermochemical decomposition of organic material at elev...
204 citations
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...[33] independently performed meta-analyses and reported...
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References
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TL;DR: Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogen-containing waste.
Abstract: Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen is lost to air, water, and land to cause a cascade of environmental and human health problems. Simultaneously, food production in some parts of the world is nitrogen-deficient, highlighting inequities in the distribution of nitrogen-containing fertilizers. Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogen-containing waste.
5,249 citations
"Effects of biochar application on s..." refers background in this paper
...Because N deposition increased from ~34 Tg N yr 1 in 1860–100 Tg N yr 1 in 1995 and is predicted to reach 200 Tg N yr 1 in 2050 (Galloway et al., 2008; IPCC, 2013), the interactive effects between biochar and N addition may dramatically influence soil microbial community structure and ecosystem functioning as well as soil GHG fluxes in the future (Liu et al....
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...Because N deposition increased from ~34 Tg N yr 1 in 1860–100 Tg N yr 1 in 1995 and is predicted to reach 200 Tg N yr 1 in 2050 (Galloway et al., 2008; IPCC, 2013), the interactive effects between biochar and N addition may dramatically influence soil microbial com- munity structure and ecosystem…...
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TL;DR: The approximate sampling distribution of the log response ratio is given, why it is a particularly useful metric for many applications in ecology, and how to use it in meta-analysis are discussed.
Abstract: Meta-analysis provides formal statistical techniques for summarizing the results of independent experiments and is increasingly being used in ecology. The response ratio (the ratio of mean outcome in the experimental group to that in the control group) and closely related measures of proportionate change are often used as measures of effect magnitude in ecology. Using these metrics for meta-analysis requires knowledge of their statistical properties, but these have not been previously derived. We give the approximate sampling distribution of the log response ratio, discuss why it is a particularly useful metric for many applications in ecology, and demonstrate how to use it in meta-analysis. The meta-analysis of response-ratio data is illustrated using experimental data on the effects of increased atmospheric CO2 on plant biomass responses.
3,042 citations
"Effects of biochar application on s..." refers methods in this paper
...We followed the methods used by Hedges et al. (1999) and Luo et al. (2006) to evaluate the responses of soil CO2, CH4, and N2O fluxes to biochar application....
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TL;DR: On the climate change mitigation front, the incorporation of ‘biochar’ into the soil is one idea gaining support, and Johannes Lehmann argues that trapping biomass carbon in this way is more effective than storing it in plants and trees that will one day decompose.
Abstract: Locking carbon up in soil makes more sense than storing it in plants and trees that eventually decompose, argues Johannes Lehmann. Can this idea work on a large scale? With the rash of IPCC reports in climate much in the news, geoengineering — the deliberate large-scale modification of the environment — is now being taken seriously in scientific and political circles that would previously have scoffed at the notion. Oliver Morton reports on the state of play in the field [News Feature p. 132] On the climate change mitigation front, the incorporation of ‘biochar’ into the soil is one idea gaining support. Johannes Lehmann argues that trapping biomass carbon in this way is more effective than storing it in plants and trees that will one day decompose. The latest IPCC report — round 3 — is covered in the News pages this week.
2,117 citations
"Effects of biochar application on s..." refers background in this paper
...Bio- char is a carbon-rich, charcoal-like product produced by burning biomass in the absence of oxygen (Lehmann, 2007b; Laird et al., 2009); it contains a high proportion of recalcitrant organic C and is stable for hundreds to thousands of years after it is applied to soil (Schmidt et al., 2002)....
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...…C sequestration, and provide other benefits, such as improving soil fertility, retaining soil moisture, and increasing crop yields (Marris, 2006; Lehmann, 2007a; Laird, 2008; Woolf et al., 2010; Mukherjee et al., 2014; Reverchon et al., 2014; Bai et al., 2015a,b; Xu et al., 2015a,b; Darby et…...
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TL;DR: In this article, the economic potential of agricultural practices, such as water and rice management, set-aside, land use change and agroforestry, livestock management and manure management, is estimated.
Abstract: Agricultural lands occupy 37% of the earth's land surface. Agriculture accounts for 52 and 84% of global anthropogenic methane and nitrous oxide emissions. Agricultural soils may also act as a sink or source for CO2, but the net flux is small. Many agricultural practices can potentially mitigate greenhouse gas (GHG) emissions, the most prominent of which are improved cropland and grazing land management and restoration of degraded lands and cultivated organic soils. Lower, but still significant mitigation potential is provided by water and rice management, set-aside, land use change and agroforestry, livestock management and manure management. The global technical mitigation potential from agriculture (excluding fossil fuel offsets from biomass) by 2030, considering all gases, is estimated to be approximately 5500–6000 Mt CO2-eq. yr−1, with economic potentials of approximately 1500–1600, 2500–2700 and 4000–4300 Mt CO2-eq. yr−1 at carbon prices of up to 20, up to 50 and up to 100 US$ t CO2-eq.−1, respectively. In addition, GHG emissions could be reduced by substitution of fossil fuels for energy production by agricultural feedstocks (e.g. crop residues, dung and dedicated energy crops). The economic mitigation potential of biomass energy from agriculture is estimated to be 640, 2240 and 16 000 Mt CO2-eq. yr−1 at 0–20, 0–50 and 0–100 US$ t CO2-eq.−1, respectively.
2,002 citations