Biochar implications for sustainable agriculture and environment: A review

Semida, Wael M.; Beheiry, Hamada R.; Sétamou, Mamoudou; Simpson, Catherine R.; Abd El-Mageed, Taia A.; Rady, Mostafa M.; Nelson, Shad D.

doi:10.1016/j.sajb.2019.11.015

Cited by 234Soil Carbon and Nitrogen DynamicsAgricultural Science and FertilizationThermochemical Biomass Conversion Processes

Biochar implications for sustainable agriculture and environment: A review

Open access

Semida, Wael M., Beheiry, Hamada R., Sétamou, Mamoudou, Simpson, Catherine R., Abd El-Mageed, Taia A., Rady, Mostafa M., Nelson, Shad D.·2019·South African Journal of Botany

DOI 10.1016/j.sajb.2019.11.015

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Abstract

Sustainable agriculture, characterized by farming profitably while minimizing damage to the environment, is not easy to practice. “Conventional agriculture” worldwide is commonly considered to involve numerous practices that have potential to damage the environment. “Sustainable agriculture” attempts to find a range of conservation agricultural practices which may mitigate some of the adverse impacts of land use intensification. Among the wide range of the conservation agricultural practices, biochar may prove a key and accessible input for sustainable agriculture, as it could efficiently sequester large amount of carbon in soil over the long-run, thus improving soil fertility, crop productivity, and mitigate global warming. In addition, biochar may enhance crop productive capacity of soils under different biotic and abiotic stresses, and advance global food security. The main focus of this report is providing a critical scientific review of the current state of knowledge regarding the effects of biochar application to soils on soil properties, processes and functions. Wider issues, including atmospheric emissions and occupational health and safety associated to biochar production and handling, are put into context. The aim of this review is to provide a sound scientific basis for policy development, to identify gaps in current knowledge, and to recommend further research relating to biochar application to soils.

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TL;DR

This review synthesizes evidence that biochar can improve soil physical, chemical, and biological properties, crop growth and yield, stress resistance, and greenhouse-gas mitigation, but effects vary strongly with feedstock, pyrolysis conditions, application rate, soil, and crop. It concludes that biochar has substantial potential for sustainable agriculture, yet careful selection and more mechanistic, long-term research are needed.

Key findings

Biochar effects on greenhouse-gas emissions are inconsistent: some studies report reduced CO₂, CH₄, and N₂O emissions, while others find no effect or increased CO₂. For example, Rondon et al. (2005) observed virtually complete suppression of CH₄ emissions from grass and soybean at 20 g kg⁻¹ biochar, with N₂O reduced by 50% and 80% for soybean and grass, respectively; Spokas and Reicosky (2009) found no consistent trends across 16 biochar types.
As a soil amendment, biochar can increase surface area up to 4.8 times that of adjacent soils (Liang et al., 2006), increase specific surface area up to 18% in a clayey soil at rates up to 20 g kg⁻¹ (Laird et al., 2010), and decrease bulk density of sand and clay by 17% and 20%, respectively (Barnes et al., 2014). It can also increase water-holding capacity by 11% in a silt loam (Karhu et al., 2011) and available water capacity by 97% in a sandy soil (Uzoma et al., 2011b).
Crop yield responses are often positive but variable: a meta-analysis found an overall ~10% significant grain-yield improvement, with poultry litter biochar best (+28%) and biosolids negative (−28%) (Jeffery et al., 2011). Maize grain increased by 150% and 98% at 15 and 20 t ha⁻¹ biochar (Uzoma et al., 2011a), while durum wheat biomass and grain yield increased up to 30% at 30–60 t ha⁻¹ (Vaccari et al., 2011).
Biochar can mitigate biotic and abiotic stresses, including drought, salinity, and heavy metals, and suppress disease in many pathosystems. Bonanomi et al. (2015) reported positive disease-reduction effects in about 85% of 13 reviewed pathosystems, neutral effects in 12%, and induced disease in 3%; however, an inverted U-shaped dose response is common, and high rates can worsen disease, e.g., 18% biochar increased tomato bacterial canker lesions to 15.1 lesions plant⁻¹ versus 8.6 in untreated controls (Frenkel et al., 2017).

Methods

Design: critical scientific review of the current state of knowledge on biochar application to soils, focusing on soil properties, processes, and functions; greenhouse-gas emissions; plant growth; and resistance to biotic and abiotic stresses.
Data/sample: selected refereed scientific publications, with a summary table of recently reported biochar studies; the review also cites existing meta-analyses and field, greenhouse, and incubation studies.
Main analysis: narrative synthesis and tabulation of literature, with the stated aims of providing a scientific basis for policy development, identifying knowledge gaps, and recommending further research.

Limitations

Stated in the paper: biochar effects are inconsistent and vary with biochar type, soil properties, crop, site conditions, and application rate; care should be taken when interpreting and extrapolating laboratory or field results to large field scale. Most available studies are short-term (1–2 years), and more long-term experiments are needed; mechanisms of biochar interactions and plant–soil relationships require further research.
Evident from the text: as a narrative review, no formal systematic search strategy, study-quality appraisal, or quantitative synthesis is described, so conclusions rely on selected studies and cited meta-analyses.
Evident from the text: the reviewed studies differ widely in feedstock, pyrolysis conditions, application rate, soil type, and crop species, which makes broad generalization difficult and likely contributes to the inconsistent outcomes reported.

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Crossref · 10.1016/j.sajb.2019.11.015

Cites

Statistics

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Claims the paper makes

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Findingcitation
Dempster et al. (2012) noted significant (20 and 25%) decreases in NH4+ and NO3− leaching when biochar with CEC of ~10 cmolc kg−1 was added to a sandy soil with CEC of ~2 cmolc kg−1.
“Dempster et al., (2012) noted significant (20 and 25%) decreases in NH 4 + and NO 3 À leaching when biochar with CEC of ~10 cmolc kg À1 was added to a sandy soil with CEC of ~2 cmolc kg À1 .”
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Findingcitation
Biochar amendment decreased soil bulk density in two consecutive cycles of rice growth.
“In a two-year field study on rice, biochar amendment decreased soil bulk density in two consecutive cycles of rice growth (Zhang et al., 2012a).”
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Findingcitation
A long-term, 500 days, soil column incubation experiment indicated increases in specific surface area (up to 18%) of an amended clayey soil when hardwood biochar was applied at rates up to 20 g kg−1.
“A long-term, 500 days, soil column incubation experiment indicated increases in specific surface area (up to 18%) of an amended clayey soil when hardwood biochar was applied at rates up to 20 g kg À1 (Laird et al., 2010).”
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Findingcitation
Biochar addition increased water-holding capacity by 11% compared to the unamended control.
“In a field study with Birch (Betula spp.) biochar incorporated into a silt loam soil in Finland, biochar addition increased water-holding capacity by 11% compared to the unamended control (Karhu et al., 2011).”
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Findingcitation
Hardwood biochar-amended soil showed greater water retention (up to 15%) at gravity-drained equilibrium and −100 and −500 kPa soil water potentials compared to unamended controls.
“For example, in a long-term column incubation study on Clarion soil, Laird et al. (2010) reported that hardwood biochar-amended soil showed greater water retention (up to 15%) at gravity-drained equilibrium and À100 and À500 kPa soil water potentials compared to unamended controls.”
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Findingcitation
Biochar addition reduced N fertilizer inputs by up to 90% while maintaining productivity.
“In a study aimed at determining the interaction effects of a matrix of biochar and N application rates on wheat and radish biomass and N uptake, biochar addition reduced N fertilizer inputs by up to 90% while maintaining productivity (Van Zwieten et al., 2010a).”
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Findingcitation
Application of biochar derived from bamboo into a sludge composting system increased the retention of N in the compost.
“The application of biochar derived from bamboo (Bambuseae spp.) into a sludge composting system increased the retention of N in the compost (Hua et al., 2009).”
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Interpretationreasoning
Biochar may advance global food security.
“In addition, biochar may enhance crop productive capacity of soils under different biotic and abiotic stresses, and advance global food security.”
Quote in the paperSubstantial claim
Premisecitation
Biochar addition can improve soil fertility.
“It has also recently been demonstrated that biochar addition can improve soil fertility, soil water-holding capacity and nutrient uptake, while sequestrating carbon and reducing greenhouse gas emissions (Barnes et al., 2014;Chan et al., 2007;Clough et al., 2013;Kloss et al., 2014;Mukherjee and Lal, 2013;Steiner et al., 2008b;Van Zwieten et al., 2010a;Zhang and Ok, 2014).”
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Premisecitation
Biochar addition can improve nutrient uptake.
“It has also recently been demonstrated that biochar addition can improve soil fertility, soil water-holding capacity and nutrient uptake, while sequestrating carbon and reducing greenhouse gas emissions (Barnes et al., 2014;Chan et al., 2007;Clough et al., 2013;Kloss et al., 2014;Mukherjee and Lal, 2013;Steiner et al., 2008b;Van Zwieten et al., 2010a;Zhang and Ok, 2014).”
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Premisecitation
Biochar addition can sequester carbon.
“It has also recently been demonstrated that biochar addition can improve soil fertility, soil water-holding capacity and nutrient uptake, while sequestrating carbon and reducing greenhouse gas emissions (Barnes et al., 2014;Chan et al., 2007;Clough et al., 2013;Kloss et al., 2014;Mukherjee and Lal, 2013;Steiner et al., 2008b;Van Zwieten et al., 2010a;Zhang and Ok, 2014).”
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Premisecitation
The effectiveness of biochar application to mitigate climate change depends on its relative recalcitrance against microbial activity, and thus on its slower return of terrestrial organic carbon as CO2 to the atmosphere.
“Lehmann, 2007a) added the understanding that the effectiveness of biochar application to mitigate climate change depends on its relative recalcitrance against microbial activity, and thus on its slower return of terrestrial organic carbon as CO 2 to the atmosphere.”
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Premisecitation
Biochar properties vary greatly depending on feedstock, pyrolysis conditions, enrichment, and grinding.
“Of concern is the great variability in biochars; not only in their nutrient availability and pH, but also in their chemical (Gwenzi et al., 2014;Nguyen et al., 2010), and physical characteristics (Downie et al., 2009), depending on the nature of the feedstock, pyrolysis conditions, whether it is enriched with other compounds, and/or how finely it is ground (Beesley et al., 2011;Uchimiya et al., 2”
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Premisecitation
Biochar application was reported to decrease emissions of CH4 and N2O from soils.
“In addition to the beneficial effects of drawing CO 2 from the atmosphere, biochar application was reported to decrease emissions of CH 4 and N 2 O from soils (Cavigelli and Robertson, 2001;Karhu et al., 2011;Liu et al., 2011;Rogovska et al., 2011;Rondon et al., 2006Rondon et al., , 2005;;Zhang et al., 2012a).”
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Premisecitation
The net energy of the pyrolysis process is highly positive, generating much more energy than is consumed.
“The net energy of the pyrolysis process is highly positive, by which, generating much more energy than is consumed.”
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- cites Roberts et al., 2010 source
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Interpretationnone given
Biochar may enhance crop productive capacity of soils under different biotic and abiotic stresses.
“In addition, biochar may enhance crop productive capacity of soils under different biotic and abiotic stresses, and advance global food security.”
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Premisecitation
Biochar addition can reduce greenhouse gas emissions.
“It has also recently been demonstrated that biochar addition can improve soil fertility, soil water-holding capacity and nutrient uptake, while sequestrating carbon and reducing greenhouse gas emissions (Barnes et al., 2014;Chan et al., 2007;Clough et al., 2013;Kloss et al., 2014;Mukherjee and Lal, 2013;Steiner et al., 2008b;Van Zwieten et al., 2010a;Zhang and Ok, 2014).”
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Interpretationcitation
To considerably increase long-term carbon sequestration, biomass needs to be pyrolysed into a relatively more stable form of carbon, such as biochar.
“Therefore, in order to considerably increase long-term C sequestration, biomass needs to be pyrolysed into a relatively more stable form of carbon, such as biochar (Lee et al., 2010;Spokas and Reicosky, 2009).”
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Interpretationreasoning
Biochar application mitigates global warming.
“Among the wide range of the conservation agricultural practices, biochar may prove a key and accessible input for sustainable agriculture, as it could efficiently sequester large amount of carbon in soil over the long-run, thus improving soil fertility, crop productivity, and mitigate global warming.”
Quote in the paperSubstantial claim
Premisecitation
Biochar addition can improve soil water-holding capacity.
“It has also recently been demonstrated that biochar addition can improve soil fertility, soil water-holding capacity and nutrient uptake, while sequestrating carbon and reducing greenhouse gas emissions (Barnes et al., 2014;Chan et al., 2007;Clough et al., 2013;Kloss et al., 2014;Mukherjee and Lal, 2013;Steiner et al., 2008b;Van Zwieten et al., 2010a;Zhang and Ok, 2014).”
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Premisecitation
Significant decrease in the leaching of fertilizers has been reported after biochar addition to soil.
“Significant decrease in the leaching of fertilizers has been reported after biochar addition to soil (Lehmann et al., 2003).”
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Premisenone given
When biochar is incorporated to the soil, its contribution to the physical nature of the soil system may be significant, influencing the soil's surface area, porosity, pore-size distribution, bulk density, water holding capacity and penetration resistance.
“When biochar is incorporated to the soil, its contribution to the physical nature of the soil system may be significant, influencing the soil's surface area, porosity, pore-size distribution, bulk density, water holding capacity and penetration resistance.”
Quote in the paperSubstantial claim
Premisecitation
Biochars with a high surface area and a high volume of macropores (>50 nm diameter) can have a high water-holding capacity.
“Biochars with a high surface area and a high volume of macropores (>50 nm diameter) can have a high water-holding capacity (Joseph et al., 2009).”
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Premisecitation
Cation exchange capacities in biochars ranges from negligible to approximately 40 cmolc g−1.
“Cation exchange capacities in biochars ranges from negligible to approximately 40 cmol c g À1 (Lehmann, 2007a).”
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Premisecitation
The influence of biochar additions on nutrient availability to plants is not entirely clear as both increasing and decreasing nutrient uptake and biomass production have been reported depending on the quality and rate of biochar applied.
“However, the influence of biochar additions on nutrient availability to plants is not entirely clear as both increasing and decreasing nutrient uptake and biomass production have been reported depending on the quality and rate of biochar applied (Bruun et al., 2012;Kloss et al., 2014;Streubel et al., 2011).”
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Premisecitation
The chemical and physical properties of biochars can vary markedly depending upon feedstock types, pyrolysis conditions, whether it is enriched with other compounds, and/or how finely it is ground.
“It is increasingly recognized that the chemical and physical properties of biochars can vary markedly depending upon feedstock types, pyrolysis conditions, whether it is enriched with other compounds, and/or how finely it is ground (Lehmann et al., 2011a;Mukherjee et al., 2011;Barrow 2012;Alburquerque et al., 2014).”
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Premisecitation
Biochar application can also effectively absorb ammonia (NH3), reducing its loss through volatilization.
“Biochar application can also effectively absorb ammonia (NH 3 ), reducing its loss through volatilization (Mandal et al., 2018;Stavi and Lal, 2013).”
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Premisecitation
Biochar incorporation to soil can enhance soil surface area up to 4.8 times that of adjacent soils.
“Biochar incorporation to soil can enhance soil surface area up to 4.8 times that of adjacent soils (Liang et al., 2006).”
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Premisereasoning
Increasing pyrolysis temperature increased the proportion of aromatic C in the biochar, due to the increase in volatile matter losses.
“Increasing pyrolysis temperature increased the proportion of aromatic C in the biochar, due to the increase in volatile matter losses.”
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Premisecitation
Enhanced biological nitrogen fixation (BNF) by legumes following biochars addition to soils has been reported.
“Enhanced biological nitrogen fixation (BNF) by legumes following biochars addition to soils has been also reported (Mia et al., 2014;Mitchell et al., 2015;Ogawa and Okimori, 2010;Tagoe et al., 2008;Zavalloni et al., 2011).”
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Premisecitation
A marked shift in microbial community composition and bacterial-to-fungal ratio has been observed in biochar-amended soil as C/N ratios became wider.
“A marked shift in microbial community composition and bacterial-to-fungal ratio, has been observed in biochar-amended soil as C/N ratios became wider (Thies and Rilling, 2009).”
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Premisecitation
Biochars, as soil amendments, can potentially have a positive effect on diazotrophs (N2-fixing bacteria).
“Biochars, as soil amendments, can potentially have a positive effect on diazotrophs (N 2 -fixing bacteria).”
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Premisecitation
Muhammad et al. (2014) reported a significant positive correlation (r2 = 0.68; p < 0.05) of bacterial-to-fungal ratio with soil C/N ratio from slow pyrolysed biochars (500 °C) produced from swine manure, fruit peels, Brassica raba residues, and reed grass (Phragmites australis) that were incorporated to sandy loam soils.
“Muhammad et al. (2014) reported a significant positive correlation (r 2 = 0.68; p < 0.05) of bacterial-to-fungal ratio with soil C/N ratio from slow pyrolysed biochars (500 °C) produced from swine manure, fruit peels, Brassica raba residues, and reed grass (Phragmites australis) that were incorporated to sandy loam soils.”
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Premisenone given
The availability of other toxic elements to plant growth (i.e., Al, Cu, Fe, Ni, Co, Pb and Mn) can be reduced by biochar addition.
“Whereas the availability of other toxic elements to plant growth (i.e., Al, Cu, Fe, Ni, Co, Pb and Mn) can be reduced by biochar addition,”
Quote in the paperSubstantial claim
Premisecitation
A significant 29% increase in microbial biomass carbon in response to willow wood biochar amendment produced at 700 °C in sandy loam soil was reported.
“In another study, a significant 29% increase in microbial biomass carbon in response to willow wood biochar amendment produced at 700 °C in sandy loam soil was reported (Ameloot et al., 2013).”
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Premisecitation
Total C and N in biochar were found to vary broadly according to feedstock, with values between 172-905 and 1.8-56.4 g kg−1 respectively, as reviewed by Chan and Xu (2009) for a variety of feedstocks materials.
“Total C and N in biochar were found to vary broadly according to feedstock, with values between 172 -905 and 1.8 -56.4 g kg À1 respectively, as reviewed by Chan and Xu (2009) for a variety of feedstocks materials.”
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Premisecitation
The availability of some nutrients to plants, particularly in acidic soils, such as N, P, K, Ca, Mg and Mo can be increased by biochar incorporation.
“The availability of some nutrients to plants, particularly in acidic soils, such as N, P, K, Ca, Mg and Mo can be increased by biochar incorporation (Atkinson et al., 2010;Kloss et al., 2014;Steiner et al., 2007b;Zhai et al., 2014).”
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Premisecitation
The nature of these carbon structures is the main reason for the high stability of the biochars.
“The nature of these carbon structures is the main reason for the high stability of the biochars (Nguyen et al., 2010).”
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Premisecitation
Biochars produced through a slow pyrolysis process at temperature of >500 °C from various feedstocks with lower ligno-cellulosic contents (i.e., manure, fruit peels, leaf litter) resulted in greater microbial biomass in biochar-amended soils.
“Some other studies also reported that biochars produced through a slow pyrolysis process at temperature of >500 °C from various feedstocks with lower ligno-cellulosic contents (i.e., manure, fruit peels, leaf litter) resulted in greater microbial biomass in biochar-amended soils (Ameloot et al., 2013;Domene et al., 2014;Luo et al., 2013).”
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Premisecitation
Dempster et al. (2012) reported a significant 28% reduction in microbial biomass carbon in response to (Eucalyptus marginata) biochar amendment produced at 600 °C in coarse-textured sandy soil.
“In contrast, Dempster et al. (2012) reported a significant 28% reduction in microbial biomass carbon in response to (Eucalyptus marginata) biochar amendment produced at 600 °C in coarse-textured sandy soil.”
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Premisecitation
Depending on feedstock type and production conditions, addition of biochars to soils could have a potential harmful toxic effect on soil microorganisms due to bio-oils and re-condensed organic compounds adsorbed on the surfaces of some biochars.
“However, depending on feedstock type and production conditions, addition of biochars to soils could have a potential harmful toxic effect on soil microorganisms due to bio-oils and re-condensed organic compounds adsorbed on the surfaces of some biochars (McClellan et al., 2007).”
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Premisecitation
Steiner et al. (2007a) reported linear increases in microbial efficiency over a range of biochars application rates from 50 to 150 g kg−1 of soil.
“For instance, Steiner et al. (2007a) reported linear increases in microbial efficiency over a range of biochars application rates from 50 to 150 g kg À1 of soil.”
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Premisecitation
Biochar's high surface area and its ability to adsorb nutrients provides a highly favorable habitat to microorganisms such as bacteria, actinomycetes and arbuscular mycorrhizal fungi to colonize, grow and reproduce.
“Biochar's high surface area and its ability to adsorb nutrients, provides a highly favorable habitat to microorganisms such as bacteria, actinomycetes and arbuscular mycorrhizal fungi to colonize, grow and reproduce (Kookana et al., 2011;Thies and Rilling, 2009).”
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Premisecitation
In the nursery tray experiment, disease symptoms were not significantly lower at 3% biochar (6.4 lesions per plant) and 6% biochar (9.4 lesions per plant) compared to the untreated control.
“were not significantly lower at 3% (6.4 lesions plants -1 ) and 6% biochar (9.4 lesions plants -1 )”
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Study design and conductcitation
Disease severity assessed as the number of blisters per plant is a reliable disease severity assessment method.
“disease severity was evaluated as the number of blisters on each plant which has been shown to be a reliable disease severity assessment method (Frenkel et al., 2016).”
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Premisecitation
Pepper plant growth (i.e., leaf area, canopy dry weight, number of nodes, and yields of buds, flowers and fruit) in the biochar-treated pots was significantly enhanced by biochar application at a level of 1-5% by weight.
“Also, Graber et al. (2010) have reported that pepper plant growth (i.e., leaf area, canopy dry weight, number of nodes, and yields of buds, flowers and fruit) in the biochar-treated pots was significantly enhanced by biochar application at a level of 1À5% by weight, and with mustard chicken manure-derived biochar increased plant dry biomass by 353 and 572% for shoot and root, respectively with 1%”
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Premisecitation
Biochar made from biosolids, corn stover, eucalyptus, fresh pine or willow pyrolysed at 550 °C and incorporated into Manawatu fine sandy loam or Waitarere sand at rates from 0 to 10 t/ha did not significantly affect the germination of maize seeds.
“In contrast, biochar made from biosolids, corn stover, eucalyptus, fresh pine or willow pyrolysed at 550 °C and incorporated into Manawatu fine sandy loam or Waitarere sand at rates from 0 to 10 t/ha did not significantly affect the germination of maize seeds (Free et al., 2010).”
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Premisecitation
In the nursery tray experiment, disease symptoms in the untreated control averaged 8.6 lesions per plant.
“the disease symptoms in the untreated control was averaged 8.6 lesions plants -1”
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- cites Frenkel et al., 2017 source
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- cites Frenkel et al., 2016 source
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Premisecitation
Mustard chicken manure-derived biochar increased plant dry biomass by 353 and 572% for shoot and root, respectively with 1% of biochar addition.
“and with mustard chicken manure-derived biochar increased plant dry biomass by 353 and 572% for shoot and root, respectively with 1% of biochar addition.”
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- cites Graber et al., 2010 source
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Premisecitation
Growth of wheat, soybean and radish was increased with a dose application of 10 ton paper mill biochar ha−1.
“In a glasshouse study, Van Zwieten et al. (2010) reported that growth of wheat, soybean and radish was increased with a dose application of 10 ton paper mill biochar ha -1 .”
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- cites Van Zwieten et al., 2010
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Premisecitation
Among 9 biochars manufactured from rice straw, poultry manure, neem leaves, wheat straw, vegetable waste, cotton sticks, citrus leaves, household waste, and eucalyptus leaves, only vegetable waste biochar (at 2% w/w on dry weight basis) had a positive effect (14.4% increase) on maize seed germination.
“In addition, among 9 biochars manufactured from rice straw, poultry manure, neem leaves, wheat straw, vegetable waste, cotton sticks, citrus leaves, household waste, and eucalyptus leaves, only vegetable waste biochar (at 2% w/w on dry weight basis) had a positive effect (14.4% increase) on maize seed germination (Qayyum et al., 2014).”
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- cites Qayyum et al., 2014
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Premisecitation
Improvements in soil quality have often resulted, with biochar application, in enhanced seed emergence and plant growth establishment.
“Improvements in soil quality have often resulted, with biochar application, in enhanced seed emergence and plant growth establishment (Solaiman et al., 2012;Van Zwieten et al., 2010b).”
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- cites Solaiman et al., 2012 source
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- cites Van Zwieten et al., 2010b
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Premisecitation
After 10 weeks of growth, an activated wood biochar, pyrolysed at 550 °C and applied at rates from 5-15 g kg−1 soil had no any significant effect on the dry matter yield of maize plants, even at the highest rate of application.
“After 10 weeks of growth, an activated wood biochar, pyrolysed at 550 °C and applied at rates from 5-15 g kg -1 soil had no any significant effect on the dry matter yield of maize plants, even at the highest rate of application (Namgay et al., 2010).”
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- cites Namgay et al., 2010 source
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Premisenone given
At present, limited works have reported either stimulation or inhibition on seed germination, depending on soil and biochar types and pyrolysis conditions associated with the biochars tested.
“At present, limited works have reported either stimulation or inhibition on seed germination, depending on soil and biochar types and pyrolysis conditions associated with the biochars tested.”
Quote in the paperNot a substantial claim
Premisecitation
Addition of biochar to soil increased seed germination by 100% with increasing biochar-application rate from 0.5 to 7.5% w/w on a dry weight basis.
“Alburquerque et al. (2014) evaluated the effects of biochars produced from five agricultural and forestry wastes on Helianthus annuus (L.) seed germination and found that addition of biochar to soil increased seed germination by 100% with increasing biochar-application rate from 0.5 to 7.5% w/w on a dry weight basis.”
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- cites Alburquerque et al., 2014 source
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Premisecitation
In the nursery tray experiment, no differences were detected in plant biomass.
“No differences were detected in plant biomass”
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- cites Frenkel et al., 2017 source
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- cites Frenkel et al., 2016 source
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Premisecitation
Aqueous extracts of six biochars produced from varied feedstocks, thermochemical processes, and temperatures had no effect on percent germination of Zea mays grains.
“In another germination experiment, it was shown that aqueous extracts of six biochars produced from varied feedstocks, thermochemical processes, and temperatures had no effect on percent germination of Zea mays grains (Rogovska et al., 2012), however, there was an increased seed germination of potato (Bamberg et al., 1986).”
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- cites Rogovska et al., 2012 source
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Premisecitation
In the nursery tray experiment, disease symptoms were significantly higher at 18% biochar (15.1 lesions per plant) compared to the untreated control (8.6 lesions per plant).
“but were significantly higher at biochar level of 18% (15.1 lesions plants -1 ) compared to the untreated control (8.6 lesions plants -1 )”
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- cites Frenkel et al., 2017 source
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- cites Frenkel et al., 2016 source
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Premisecitation
Biochar (corn cob biochar produced at 450 °C by slow pyrolysis technique) applied at 20 t ha−1 did not significantly improve growth of Soybean (Glycine max L.) on a sandy loam soil.
“while biochar (corn cob biochar produced at 450 °C by slow pyrolysis technique) applied at 20 t ha -1 did not significantly improve growth of Soybean (Glycine max L.) on a sandy loam soil (Hafeez et al., 2017).”
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- cites Hafeez et al., 2017
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Premisecitation
Increasing soybean plants growth (34-41% increases in root and shoot dry weights) on soil amended with 2% (w/w) biochar.
“This was in contrast to increasing soybean plants growth (34À41% increases in root and shoot dry weights) on soil amended with 2% (w/w) biochar (Egamberdieva et al., 2016).”
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- cites Egamberdieva et al., 2016 source
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Premisecitation
Biochar type and application rates had a significant effect on early growth of wheat, mung beans and clover.
“In a laboratory bioassay, it has been demonstrated that biochar type and application rates had a significant effect on early growth of wheat, mung beans and clover (Solaiman et al., 2012).”
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- cites Solaiman et al., 2012 source
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Premisecitation
Biochar somewhat improved the permanent wilting point.
“biochar somewhat improved the permanent wilting point (Abel et al., 2013;Cornelissen et al., 2013)”
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- cites Abel et al., 2013 source
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- cites Cornelissen et al., 2013 source
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Premisereasoning
Soil application of biochars, depending on their qualities, may affect chemical and biological soil properties, thus affecting the redistribution of heavy metals among solid-phase components.
“Soil application of biochars, depending on their qualities, may affect chemical and biological soil properties, thus affecting the redistribution of heavy metals among solid-phase components.”
Quote in the paperSubstantial claim
Interpretationcitation
The nursery tray experiment provides additional evidence for a U-shaped dose/response for foliar pathogens.
“elucidating additional evidence for a U shape dose/ response for foliar pathogens”
Quote in the paperSubstantial claim
Premisecitation
The effects of biochar applications depend on various factors such as soil and metal types, type of feedstocks used for charring, pyrolysis conditions and amount of biochars applied to soils.
“Specifically, the effects of biochars applications depend on various factors such as soil and metal types, the type of feedstocks used for charring, pyrolysis conditions and the amount of biochars applied to soils (Al-Wabel et al., 2015;Park et al., 2011).”
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- cites Al-Wabel et al., 2015 source
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- cites Park et al., 2011 source
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Interpretationcitation
High levels of biochar applied to growth media might be questionable in the presence of a foliar pathogen.
“strengthening the point that high levels of biochar applied to growth media might be questionable in the presence of a foliar pathogen.”
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Premisecitation
Plants of A. theophrasti receiving both biochar at 50 t ha-1 and salts at 30 g m-2 NaCl had growth rates similar to plants devoid of salt addition.
“Thomas et al. (2013) reported that plants of A. theophrasti receiving both biochar (at a level of 50 t ha À1 ) and salts (at a concentration of 30 g m -2 of NaCL) had growth rates similar to plants devoid of salt addition.”
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- cites Thomas et al., 2013 source
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Premisecitation
Biochar application at high rates can mitigate adverse effects of salt stress for plant growth.
“Biochar application at high rates can mitigate adverse effects of salt stress for plant growth (Akhtar et al., 2015;Kim et al., 2016).”
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- cites Akhtar et al., 2015
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- cites Kim et al., 2016 source
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Premisecitation
Biochar application in poor sandy soils improved plant growth by improving soil-plant water relations under well-watered and drought conditions.
“Haider et al. (2015) reported that biochar application in poor sandy soils improved plant growth by improving soil-plant water relations under well-watered and drought conditions.”
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- cites Haider et al., 2015 source
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Premisecitation
Biochar application at 5% (w/w) enhanced crop productivity in salt-affected soils.
“Akhtar et al. (2015a) reported that biochar application at a level of 5% (w/w) enhanced crop productivity in salt-affected soils”
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- cites Akhtar et al., 2015a
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Interpretationreasoning
The increase in water holding capacity of biochar amended soils can be used as an indicator of the overall rise in plant available water.
“Therefore, the increase in water holding capacity (WHC) of biochar amended soils can be used as an indicator of the overall rise in plant available water (Hafeez et al., 2017;Liu et al., 2016).”
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- cites Hafeez et al., 2017
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- cites Liu et al., 2016 source
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Premisecitation
Biochar application at 5% (w/w) had positive residual effects in reducing Na+ uptake in the following wheat crop under salinity stress up to 11.8 dS m-1.
“The authors further observed positive residual effects of biochar application at a level of 5% (w/w) in reducing Na + uptake in the following wheat crop under salinity stress up to 11.8 dS m -1 (Akhtar et al., 2015).”
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- cites Akhtar et al., 2015
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Classified as probably not a substantial claim. 3

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Findingcitation
Application of mesquite wood biochar decreased hydraulic conductivity by 92% in sand and 67% in organic soil, but the hydraulic conductivity was increased by 328% in clay-rich soil.
“Interestingly, in a column study, application of mesquite wood (Prosopis sp.) biochar decreased hydraulic conductivity by 92% in sand and 67% in organic soil, but the hydraulic conductivity was increased by 328% in clayrich soil (Barnes et al., 2014).”
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- cites Barnes et al., 2014 source
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Findingcitation
Black locust biochar added to a sandy soil increased available water capacity by 97%, and saturated water content by 56%, and reduced hydraulic conductivity with increasing moisture content when compared to unamended soil.
“Black locust (Robinia pseudoacacia) biochar added to a sandy soil increased available water capacity by 97%, and saturated water content by 56%, and reduced hydraulic conductivity with increasing moisture content when compared to unamended soil (Uzoma et al., 2011b).”
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- cites Uzoma et al., 2011b
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Findingcitation
Biochar addition, especially at application rates of 150 and 225 Mg ha−1, decreased soil bulk density and increased soil field capacity, and hence positively impact plant growth and water economy.
“Biochar addition, especially at application rates of 150 and 225 Mg ha À1 , decreased soil bulk density and increased soil field capacity, and hence positively impact plant growth and water economy.”
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- cites Alburquerque et al., 2014 source
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Findingcitation
Addition of biochar decreased the bulk density of sand and clay by 17 and 20%, respectively.
“A column experiment conducted by Barnes et al. (2014) showed that addition of biochar decreased the bulk density of sand and clay by 17 and 20%, respectively.”
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- cites Barnes et al., 2014 source
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Findingcitation
Low nutrient biochar addition into soil provided significant increases in N retention in soil and uptake of N into crop biomass, which was speculated to be due to the biochar's ability to adsorb NH3 and thus minimize N loss through volatilization.
“Similarly, in a field study on sorghum (Sorghum bicolor L. Moench) Steiner et al. (2008a) reported that low nutrient biochar addition into soil provided significant increases in N retention in soil and uptake of N into crop biomass, which was speculated to be due to the biochar's ability to adsorb NH 3 and thus minimize N loss through volatilization.”
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- cites Steiner et al., 2008a
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Findingcitation
Both maize yield and agronomic N-use efficiency increased with increasing biochar rate.
“Zhang et al. (2012b) conducted a four-month field trial on maize where a nutrient rich wheat-straw biochar (20 and 40 t ha À1 ) was applied to a calcareous loamy soil, where both maize yield and agronomic N-use efficiency increased with increasing biochar rate.”
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- cites Zhang et al., 2012b
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Findingcitation
Treatment with the highest biochar application rate (11% w/w) significantly increased accumulation of NO3−-N in the soil and lowered NH4+-N across the five biochar application rates.
“In the same study, treatment with the highest biochar application rate (11% w/w) significantly increased accumulation of NO 3 À -N in the soil and lowered NH 4 + -N across the five biochar application rates.”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites Van Zwieten et al., 2010a
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Premisecitation
Effect of biochar incorporation into soil on C cycling and emission of CO2, CH4, and N2O has been inconsistent and may be either positive or negative, depending on biochar type and soil properties.
“Effect of biochar incorporation into soil C cycling and emission of CO 2 , CH 4 , and N 2 O has so far been inconsistent and may be either positive or negative, depending on biochar type and soil properties (Spokas and Reicosky, 2009;Zhang et al., 2012b;Zimmerman et al., 2011).”
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- cites Spokas and Reicosky, 2009
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- cites Zhang et al., 2012b
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- cites Zimmerman et al., 2011 source
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Interpretationcitation
Coupling the pyrolysis process with the application of biochar in soil enables the sequestration of atmospheric CO2, as more C is sequestered than emitted.
“Therefore, coupling the pyrolysis process with the application of biochar in soil actually enables the sequestration of atmospheric CO 2 , as more C is sequestered than emitted (Roberts et al., 2010;Whitman and Lehmann, 2009).”
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- cites Roberts et al., 2010 source
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- cites Whitman and Lehmann, 2009
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Premisecitation
Biochar applications could be a key input for sustaining production and simultaneously reducing pollution and dependence on fertilizers.
“The emerging literature generally supports that biochar applications could be a key input for sustaining production and simultaneously reducing pollution and dependence on fertilizers (Beesley et al., 2011;Lal, 2007Lal, , 2004;;Lehmann and Joseph, 2015;Marris, 2006;Sohi et al., 2009;Stavi and Lal, 2013).”
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- cites Beesley et al., 2011 source
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- cites Lal, 2007 source
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- cites Lehmann and Joseph, 2015
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- Rests on an assumption: Biochar application to soils is an accessible input for sustainable agriculture.
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Premisecitation
Many recent studies have documented a number of benefits with biochar amendment to soil, including increased cation exchange capacity (CEC), reduced N leaching, enhanced microbial proliferation, liming, and other advantages.
“Many recent studies have documented a number of benefits with biochar amendment to soil, including increased cation exchange capacity (CEC), reduced N leaching, enhanced microbial proliferation, liming, and other advantages (Cornelissen et al., 2013;Kloss et al., 2014;Lehmann et al., 2011b;Mia et al., 2014;Ventura et al., 2012).”
Quote in the paperSubstantial claim0 of 3 sources checked
- cites Cornelissen et al., 2013 source
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- cites Kloss et al., 2014 source
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- cites Lehmann et al., 2011b
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Interpretationreasoning
Overall, inconsistent results of the effects of biochar addition on GHGs emission from either lab incubation or field observations indicate that care should be taken to accurately interpret and extrapolate results to large field scale.
“Overall, inconsistent results of the effects of biochar addition on GHGs emission from either lab incubation or field observations indicate that care should be taken to accurately interpret and extrapolate results to large field scale.”
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Premisecitation
The effects of biochar addition on CH4 and N2O were inconsistent and have shown variability with crop and soil types, site condition, and the origin of the biochar.
“However, the effects of biochar addition on CH 4 and N 2 O were inconsistent and have shown variability with crop and soil types, site condition, and the origin of the biochar (Karhu et al., 2011;Kimetu and Lehmann, 2010;Lehmann et al., 2011b;Spokas et al., 2009;Zimmerman et al., 2011).”
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- cites Karhu et al., 2011 source
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- cites Kimetu and Lehmann, 2010
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- cites Lehmann et al., 2011b
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Premisecitation
Biochar has a high surface-area and is a highly porous material, these qualities may offer an opportunity to retain and adsorb plant nutrients and consequently improve soil fertility.
“Biochar has a high surface-area and is a highly porous material, these qualities may offer an opportunity to retain and adsorb plant nutrients and consequently improve soil fertility (Lehmann, 2007b).”
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- cites Lehmann, 2007b
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Premisenone given
Recent evidence suggests that in addition to carbon sequestration, biochar amendment positively impacts soil quality and fertility, improves nutrient cycling, reduces nutrient leaching from soil, and stimulates soil microbial activity.
“Recent evidence suggests that in addition to carbon (C) sequestration, biochar amendment positively impact soil quality and fertility, improve nutrient cycling, reduce nutrient leaching from soil, and stimulate soil microbial activity.”
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Premisecitation
The low bulk density of biochar (~300 kg m−3) and its highly stable organic carbon to soils has the potential to reduce soil bulk density and penetration resistance, and accordingly increase total soil porosity.
“It has been suggested that the low bulk density of biochar (~300 kg m À3 ) and its highly stable organic carbon to soils has the potential to reduce soil bulk density and penetration resistance, and accordingly increase total soil porosity (Gwenzi et al., 2014).”
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- cites Gwenzi et al., 2014 source
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Premisecitation
As biochar ages, biotic and abiotic oxidation results in increased surface carboxyl groups, and subsequently increases the soils ability for cation adsorption.
“As biochar ages, biotic and abiotic oxidation results in increased surface carboxyl groups, and subsequently increases the soils ability for cation adsorption (Cheng et al., 2008).”
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- cites Cheng et al., 2008 source
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Premisereasoning
Varying experimental studies indicate that different amendment rates, biochar grain size, soil properties, and/or threshold effects of amendment rate or grain size can all produce drastically different result in terms of biochar effects on soil hydrological characteristics.
“Varying experimental studies indicate that different amendment rates, biochar grain size, soil properties, and/or threshold effects of amendment rate or grain size can all produce drastically different result in terms of biochar effects on soil hydrological characteristics.”
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Premisecitation
Biochar addition to agricultural soil has been shown, in many studies, to induce soil alkalization by increasing soil pH in acidic soil, which corresponded to the increased concentration of alkaline metal oxides in the biochars and a decreased soil exchangeable Al3+ and consequently reduced the potential toxicity of Al in acidic soils.
“Biochar addition to agricultural soil has been shown, in many studies, to induce soil alkalization by increasing soil pH in acidic soil, which corresponded to the increased concentration of alkaline metal (i.e., Ca 2+ ,Mg 2+ , and K + ) oxides in the biochars and a decreased soil exchangeable Al 3+ and consequently reduced the potential toxicity of Al in acidic soils (Lehmann et al., 2003;Steiner”
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- cites Lehmann et al., 2003 source
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- cites Steiner et al., 2007b
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- cites Van Zwieten et al., 2010a
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Premisecitation
Since most of biochars show high C/N ratios (vary widely between 7 and 400), application of biochar may, indeed, increase soil C/N ratio, which may lead to N deficiency in plants and that may be reflected in lower plant yield.
“Since most of biochars show high C/N ratios (vary widely between 7 and 400), application of biochar may, indeed, increase soil C/N ratio, which may lead to N deficiency in plants and that may be reflected in lower plant yield (Kloss et al., 2014;Rondon et al., 2007).”
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- cites Kloss et al., 2014 source
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- cites Rondon et al., 2007 source
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Premisecitation
Increasing rates of biochar addition (0, 30, 60, and 90 kg ha−1) increased N2 fixation, which consequently lead to 30-40% increase in beans (Phaseolus vulgaris L.) yield.
“Increasing rates of biochar addition (0, 30, 60, and 90 kg ha À1 ) increased N 2 fixation, which consequently lead to 30À40% increase in beans (Phaseolus vulgaris L.) yield (Rondon et al., 2007).”
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- cites Rondon et al., 2007 source
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Premisecitation
In a critical review by Clough et al. (2013) for a variety of biochar and soils, biochar has been found to increase net nitrification rates, remove NH3 via adsorption, and stimulate N mineralization and immobilization.
“In a critical review by Clough et al. (2013) for a variety of biochar and soils, biochar has been found to increase net nitrification rates, remove NH 3 via adsorption, and stimulate N mineralization and immobilization.”
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- cites Clough et al., 2013 source
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Premisecitation
Biochar is hardly mineralized, and N immobilization is expected to be either negligible or transient despite the high C/N ratio.
“Biochar is hardly mineralized, and N immobilization is expected to be either negligible or transient despite the high C/N ratio (Chan and Xu, 2009).”
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- cites Chan and Xu, 2009
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Premisecitation
According to the biomass feedstock and the pyrolysis conditions, biochars can be produced at any pH between 4 and 12 and after short-term incubation of four months at 70 °C can decrease to a pH value of 2.5.
“Nevertheless, according to the biomass feedstock and the pyrolysis conditions, biochars can be produced at any pH between 4 and 12 (Lehmann, 2007b) and after short-term incubation of four months at 70 °C can decrease to a pH value of 2.5 (Cheng et al., 2006).”
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- cites Lehmann, 2007b
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- cites Cheng et al., 2006 source
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Premisecitation
Addition of biochar to soils can stimulate soil microbial activity and affect soil microbiological properties.
“The available literature so far show that the addition of biochar to soils can constitute a medium that stimulates soil microbial activity, and thus affecting soil microbiological properties.”
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Premisecitation
Addition of 10% (w/w) poultry litter biochar decreased the number of leaves, plant height, stem diameter and number of achenes for each head of sunflower (Helianthus annuus L.) plants.
“In contrast, addition of 10% (w/w) poultry litter biochar decreased the number of leaves, plant height, stem diameter and number of achenes for each head of sunflower (Helianthus annuus L.) plants (Furtado et al., 2016), while biochar (corn cob biochar produced at 450 °C by slow pyrolysis technique) applied at 20 t ha -1 did not significantly improve growth of Soybean (Glycine max L.) on a sandy”
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- cites Furtado et al., 2016 source
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Premisecitation
The density of nodule increased by 72% and 80% at 10 t ha−1 and 50 t ha−1 respectively.
“The density of nodule increased by 72% and 80% at 10 t ha À1 and 50 t ha À1 respectively (Mia et al., 2014).”
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- cites Mia et al., 2014 source
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Premisecitation
Soil application with biochar at a level of 68 t ha−1 increased biomass of rice (Oryza sativa L.) and cowpea (Vigna unguiculata (L.) Walp) by 20 and 50%, respectively, and increased cowpea biomass by 100% when biochar was applied at a level of 137 t ha−1.
“In addition, soil application with biochar at a level of 68 t ha À1 increased biomass of rice (Oryza sativa L.) and cowpea (Vigna unguiculata (L.) Walp) by 20 and 50%, respectively, and increased cowpea biomass by 100% when biochar was applied at a level of 137 t ha À1 (Glaser et al., 2002).”
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- cites Glaser et al., 2002 source
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Premisecitation
Adding biochar at 0.5 and 2.5 kg m−2 to soil increased seed germination of Palmer amaranth, but had no effect on sicklepod and southern crabgrass.
“Adding biochar at 0.5 and 2.5 kg m -2 to soil increased seed germination of Palmer amaranth (Soni et al., 2014), but had no effect on sicklepod and southern crabgrass (Soni et al., 2014).”
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- cites Soni et al., 2014 source
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Premisecitation
Biochar application for poor sandy soils improved maize plant growth by improving soil-plant water relations (improved relative water content and leaf osmotic potential) and photosynthesis (reduced stomatal resistance and stimulated photosynthesis by increasing the electron transport rate of photosystem II).
“In addition, Haider et al. (2015) have reported that biochar application for poor sandy soils improved maize plant growth by improving soil-plant water relations (improved relative water content and leaf osmotic potential) and photosynthesis (reduced stomatal resistance and stimulated photosynthesis by increasing the electron transport rate of photosystem II).”
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- cites Haider et al., 2015 source
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Premisecitation
The total amount of N fixation increased significantly by 117% (average of both single and mixed cultures) with the application of 10 t ha−1 when compared to controls, whereas the amount of N fixation was lowest at the rate of 120 t ha−1.
“They observed the total amount of N fixation increased significantly by 117% (average of both single and mixed cultures) with the application of 10 t ha À1 when compared to controls, whereas the amount of N fixation was lowest at the rate of 120 t ha À1 .”
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- cites Mia et al., 2014 source
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Premisecitation
In foliar pathogen pathosystems, only 2 out of 6 (about 33%) showed potential U-shaped relationships, whereas in soilborne pathogen pathosystems, 20 out of 24 (about 83%) showed such relationships.
“These effects were less evident in foliar pathogens where only 2 out of 6 pathosystems (about 33%) showed potential U-shaped relationships (Elad et al., 2011(Elad et al., , 2010)), whereas the relationships were very common in the soil borne pathogen pathosystems (20 out of 24 pathosystems, about 83%).”
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- cites Elad et al., 2011
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- cites Elad et al., 2010 source
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May combine two claims.
Premisereasoning
Prior works on foliar pathogens showed milder susceptibility response, essentially for only Botrytis cinerea, and were not tested at levels relevant to partial peat replacements (>10%).
“As the works on the foliar pathogens showed milder susceptibility response (essentially for only one pathogen; Botrytis cinerea) and were not tested at levels relevant to partial peat replacements (> 10%)”
Quote in the paperSubstantial claim
May combine two claims.
Premisecitation
Durum wheat (Triticum durum L.) and maize (Zea mays L.) biomasses were increased up to about 30% and 44%, respectively by biochar application.
“Further with gramineae crops, durum wheat (Triticum durum L.) and maize (Zea mays L.) biomasses were increased up to about 30% and 44%, respectively by biochar application (Oguntunde et al., 2004;Vaccari et al., 2011).”
Quote in the paperNot a substantial claim0 of 2 sources checked
- cites Oguntunde et al., 2004 source
  Not checked in the free run.
- cites Vaccari et al., 2011 source
  Not checked in the free run.
May combine two claims.
Premisecitation
Biochar has been reported to either increase or decrease plant growth, based on studies with varying factors including soil and biochar types and pyrolysis conditions associated with the biochars tested.
“Biochar has been reported to either increase (Chan et al., 2008;Yamato et al., 2006) or decrease (Deenik et al., 2010) plant growth, based on studies with varying factors including soil and biochar types and pyrolysis conditions associated with the biochars tested.”
Quote in the paperSubstantial claim0 of 3 sources checked
- cites Chan et al., 2008 source
  Not checked in the free run.
- cites Yamato et al., 2006 source
  Not checked in the free run.
- cites Deenik et al., 2010 source
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.
Interpretationnone given
The other mechanisms by which biochar improved plant growth may include improved moisture retention and availability, and reduced soil bulk density.
“The other mechanisms by which biochar improved plant growth may include improved moisture retention and availability, and reduced soil bulk density.”
Quote in the paperNot a substantial claim
May combine two claims.
Premisecitation
Biochar generally increased wheat seed germination at the lower rates of biochar application (10-50 t/ha) and decreased or had no effect at higher rates of application (50-100 t/ha).
“Biochar generally increased wheat seed germination at the lower rates of biochar application (10À50 t/ha) and decreased or had no effect at higher rates of application (50À100 t/ha).”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites Solaiman et al., 2012 source
  Not checked in the free run.
May combine two claims.
Premisecitation
Biochars derived from paper mill waste when applied at 10 t/ha (~1% on weight basis) significantly improved germination of wheat in a Ferrosol, but had no significant effect on other indicator crops including radish or soybean in either Ferrosol or Calcarosol soils.
“For instance, biochars derived from paper mill waste when applied at 10 t/ha (~1% on weight basis) either significantly improved germination of wheat in a Ferrosol, but had no significant effect on other indicator crops including radish or soybean in either Ferrosol or Calcarosol (Van Zwieten et al., 2010b) soils.”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites Van Zwieten et al., 2010b
  Not checked in the free run.
May combine two claims.
Premisecitation
Biochar addition to a fertile sandy clay loam in a boreal climate relieved temporary water deficit stress and improved harvestable yield.
“In another study, biochar addition to a fertile sandy clay loam in a boreal climate relieved the temporary water deficit stress, and improved the harvestable yield (Tammeorg et al., 2014b).”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites Tammeorg et al., 2014b
  Not checked in the free run.
May combine two claims.
Premisecitation
Biochar increased the amount of water retained at field capacity to a larger extent than water held at permanent wilting point, thereby increasing plant available water.
“while the amount of water retained at field capacity improved to a larger extent compared to the water held at permanent wilting point, i.e. increased the plant available water.”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites Abel et al., 2013 source
  Not checked in the free run.
- cites Cornelissen et al., 2013 source
  Not checked in the free run.
Probably not a substantial claim: may not pass S4 (based).
Interpretationnone given
Certain biochar/crop combinations have proven to be detrimental to plant production.
“However, certain biochar/crop combinations have proven to be detrimental to plant production.”
Quote in the paperNot a substantial claim
May combine two claims.
Interpretationcitation
Different biochar types have the potential to mitigate salinity-induced reductions in mineral uptake and may be a novel technique to mitigate adverse effects of salinization in arable and contaminated soils.
“Therefore, different biochar types have the potential to mitigate salinity-induced reductions in mineral uptake, and may be a novel technique to mitigate the adverse effects of salinization in arable and contaminated soils (Kim et al., 2016;Thomas et al., 2013).”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites Kim et al., 2016 source
  Not checked in the free run.
- cites Thomas et al., 2013 source
  Not checked in the free run.
May combine two claims.
Premisecitation
Addition of biochars significantly improved soil capacity to retain and adsorb plant nutrients and decrease leaching nutrient losses.
“It has been reported that addition of biochars significantly improved soil capacity to retain and adsorb plant nutrients and decrease leaching nutrient losses (Glaser et al., 2002;Lehmann et al., 2003;Uzoma et al., 2011b).”
Quote in the paperSubstantial claim0 of 3 sources checked
- cites Glaser et al., 2002 source
  Not checked in the free run.
- cites Lehmann et al., 2003 source
  Not checked in the free run.
- cites Uzoma et al., 2011b
  Not checked in the free run.
May combine two claims.
Interpretationnone given
Composition of biochar can affect plant growth, production and soil biota; in some cases increasing soil microbial composition and in other cases causing toxic effects.
“Composition of biochar can also affect plant growth, production and soil biota; in some cases increasing soil microbial composition and in other cases causing toxic effects.”
Quote in the paperSubstantial claim
May combine two claims.
Premisecitation
Biochar additions to soils might modify some chemical soil properties, i.e. cation exchange capacity and soil acidity, thus reducing the availability of heavy metals to plants.
“Biochar additions to soils might modify some chemical soil properties (i.e., cation exchange capacity and soil acidity), thus reducing the availability of heavy metals to plants (B rendov a et al., 2015;Park et al., 2011).”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites B rendov a et al., 2015
  Not checked in the free run.
- cites Park et al., 2011 source
  Not checked in the free run.
May combine two claims.
Premisecitation
In a pot and field study on sandy loam or boreal sandy clay loam, biochar amendments at 20 or 10 t ha-1 improved seedling growth and grain yield of soybean and wheat, respectively, probably by mitigating water deficit stress.
“In a pot and field study carried out on a sandy loam or a boreal sandy clay loam, biochars soil amendments at levels of 20 or 10 t ha À1 improved seedling growth and grain yield of soybean and wheat, respectively, probably by mitigating the water deficit stress (Hafeez et al., 2017;Tammeorg et al., 2014a).”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites Hafeez et al., 2017
  Not checked in the free run.
- cites Tammeorg et al., 2014a
  Not checked in the free run.
May combine two claims.
Premisecitation
Surface functional groups and adsorption sites on biochars could increase soil CEC and consequently increase metal exchange capacity of soil through formation of complexes with cationic heavy metals.
“Paz-Ferreiro et al. (2014b) have demonstrated that the surface functional groups and adsorption sites on biochars could increase the soil CEC and consequently increase metal exchange capacity of soil through the formation of complexes with cationic heavy metals.”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites Paz-Ferreiro et al., 2014b
  Not checked in the free run.
Classified as probably not a substantial claim. May combine two claims.
Interpretationnone given
Biochars have tremendous potential in crop production both at the large-scale field production level, as well as in greenhouse pot production.
“Biochars have tremendous potential in crop production both at the large-scale field production level, as well as in greenhouse pot production.”
Quote in the paperSubstantial claim
May combine two claims.
Premisecitation
Several studies have shown that biochars improve crop productivity under normal conditions and also improve crop yield under adverse conditions such as salinity, drought and heavy metals.
“Several studies in last decades have shown that biochars not only improve crop productivity under normal conditions, but also improve crop yield under the adverse conditions such as salinity, drought and heavy metals (Haider et al., 2015;Joseph et al., 2013;Park et al., 2011;Pressler et al., 2017).”
Quote in the paperSubstantial claim0 of 3 sources checked
- cites Haider et al., 2015 source
  Not checked in the free run.
- cites Joseph et al., 2013 source
  Not checked in the free run.
- cites Park et al., 2011 source
  Not checked in the free run.
May combine two claims.
Interpretationnone given
Biochars are widely varied and can have various effects on crop growth, production, and soil properties.
“Biochars are widely varied and can have various effects on crop growth, production, and soil properties.”
Quote in the paperSubstantial claim
May combine two claims.
Premisecitation
Top dressing with biochar at 50 t ha-1 mitigated salt-induced mortality in Abutilon theophrasti and prolonged the survival rate of Prunella vulgaris.
“For instance, top dressing with biochar at 50 t ha À1 mitigated saltinduced mortality in Abutilon theophrasti and prolonged the survival rate of Prunella vulgaris.”
Quote in the paperNot a substantial claim
May combine two claims.
Premisecitation
Biochar addition significantly decreased NH4OAc- or AB-DTPA-extractable heavy metal concentrations of soils, indicating metal immobilization, and increased shoot dry biomass of maize plants by 54.5-102% at 75% FC and 133-266% at 100% FC.
“Biochar addition significantly decreased NH 4 OAc-or AB-DTPAextractable heavy metal concentrations of soils, indicating metal immobilization, increasing shoot dry biomass of maize plants by 54.5À102% at 75% FC and 133À266% at 100% FC.”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites Al-Wabel et al., 2015 source
  Not checked in the free run.
May combine two claims.
Premisecitation
Biochar application at 5% (w/w) ameliorated salt stress by adsorbing Na+ and increasing xylem K+ content, thereby increasing tuber yield in potato.
“where biochar application ameliorated salt stress by adsorbing Na + and increasing xylem K + content thereby increasing tuber yield in potato.”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites Akhtar et al., 2015a
  Not checked in the free run.
May combine two claims.
Interpretationnone given
Many of the effects of biochar have been shown to be beneficial, including growth and yield increases, adsorption of heavy metals, water holding capacity, and plant physiological responses.
“Many of the effects have been shown to be beneficial; i.e. growth and yield increases, adsorption of heavy metals, water holding capacity, and plant physiological responses.”
Quote in the paperSubstantial claim
May combine two claims.
Interpretationcitation
In the nursery tray experiment, biochar had no positive effects at any investigated level and had negative effects at the highest level.
“not only did the biochar have no positive effects at any investigated level, but it had also negative effects at the highest levels”
Quote in the paperSubstantial claim
May combine two claims.
Premisecitation
Applying biochar significantly reduced shoot heavy metal concentrations in maize plants, except Fe at 75% FC, in response to increasing application rates, with highest decreases of 51.3% and 60.5% for Mn, 28% and 21.2% for Zn, 60% and 29.5% for Cu, 53.2% and 47.2% for Cd at 75% FC and 100% FC, respectively.
“In addition, applying biochar significantly reduced shoot heavy metal concentrations in maize plants (except for Fe at 75% FC) in response to increasing application rates, with a highest decrease of 51.3% and 60.5% for Mn, 28% and 21.2% for Zn, 60% and 29.5% for Cu, 53.2% and 47.2% for Cd at soil moisture levels of 75% FC and 100% FC, respectively (Al-Wabel et al., 2015).”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites Al-Wabel et al., 2015 source
  Not checked in the free run.
May combine two claims.
Interpretationnone given
Rate of biochar addition has a great impact on crop growth and yield, but this varies by culture system and crop.
“Rate of biochar addition has a great impact on crop growth and yield, but this varies by culture system and crop.”
Quote in the paperNot a substantial claim

57 of 57

The paper relies on this without support.
Biochar application to soils is an accessible input for sustainable agriculture.
“Among the wide range of the conservation agricultural practices, biochar may prove a key and accessible input for sustainable agriculture, as it could efficiently sequester large amount of carbon in soil over the long-run, thus improving soil fertility, crop productivity, and mitigate global warming.”
The paper relies on this without support.
The use of biochar in agriculture is environmentally sustainable.
“Among the wide range of the conservation agricultural practices, biochar may prove a key and accessible input for sustainable agriculture, as it could efficiently sequester large amount of carbon in soil over the long-run, thus improving soil fertility, crop productivity, and mitigate global warming.”

2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Biochar application has positive as well as negative effects on CH4 and N2O emissions, specific to cropping system and type of biochar and processing conditions.
“Although the literature shows a positive impact in many occasions, in terms of reduced emissions, Semida et al. present mixed results, where the application of biochar has positive as well as negative effects on CH 4 and N 2 O emissions.This is specific to the cropping system as well as the type of biochar utilized and its processing conditions (Semida et al. 2019).”
From Strategies for mitigation of climate change: a review (2020) · cites this paper as Semida et al. 2019

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

Maize yield falls at the higher application rate despite a claimed increasing trend
Minor
The stated maize grain-yield gain is 150% at 15 t ha -1 but only 98% at 20 t ha -1, contradicting the claim that yield increased with increasing biochar application rate.
Tomato photosynthetic rate is reported as both improved and unaffected
Minor
The same account of Akhtar et al. (2014) says biochar significantly improved photosynthetic rate and then says leaf photosynthetic rate was not significantly affected.
Soybean germination is reported as both significantly increased and unaffected
Minor
The Hafeez et al. table entry says 20 t ha -1 significantly increased soybean germination percentage, while the text says germination percentage was not significantly affected at either 10 or 20 t ha -1.

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References 218 · Cited by 234

Research works printed but not linked: 6

Barakat, 2015, Influence of potassium humate and ascorbic acid on growth, yield and chemical composition of common bean (Phaseolus vulgaris L.) grown under reclaimed soil conditions, International Journal of Academic Research, 7, 192
Burke, 2012, The effect of source of biochar on cotton seedling growth and development, AAES Res. Ser., 610, 85
Hafeez, 2017, Effect of biochar application on seed germination and seedling growth of glycine max (L.) merr. under drought stress, Pakistan Journal of Botany, 49, 7
Hubert, 2002, agricultures et développement durable enjeux de connaissances et attitudes de recherche, Doss. l'environnement l'INRA, 27, 41
Smith, P., Martino, D., Cai, Z., Gwary, D., Janzen, H., Kumar, P., McCarl, B., Ogle, S., O'Mara, F., Rice, C., Scholes, B., Sirotenko, O., 2007. Agriculture, in: climate change 2007: mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, pp. 497–540.
2013, World Population Prospects: The 2012 Revision [WWW Document]

Authors: Semida, W. M., Beheiry, H. R., Sétamou, M., Simpson, C. R., Abd El-Mageed, T. A., Rady, M. M., & Nelson, S. D.
Affiliations: Texas A&M University – Kingsville (US)
Texas Tech University (US)
Fayoum University (EG)
Corresponding author: Semida, Wael M.
ORCID: Semida, Wael M.
Beheiry, Hamada R.
Sétamou, Mamoudou
Simpson, Catherine R.
Rady, Mostafa M.
Nelson, Shad D.
Venue: South African Journal of Botany
Publisher: Elsevier BV
Published: 2019-12
Volume: 127
Pages: 333-347
ISSN: 0254-6299 (ISSN-L)
DOI: 10.1016/j.sajb.2019.11.015
OpenAlex: W2991571050
Semantic Scholar: f1a8eb715ac3d32e4c0ca3c1328e57a040b66eac
Cited by: 234
References: 218
Citations by year: 2026: 28 · 2025: 50 · 2024: 41 · 2023: 45 · 2022: 31 · 2021: 29 · 2020: 10
FWCI: 13.90
Type: journal article
Language: en
Open access: hybrid
doi.org
Licence: cc-by
www.elsevier.com/tdm/userlicense/1.0/ (tdm)
www.elsevier.com/legal/tdmrep-license (tdm)
creativecommons.org/licenses/by/4.0/ (vor, 731 d)
Locations: South African Journal of Botany (publishedVersion, cc-by)
Topics: Life Sciences › Agricultural and Biological Sciences › Soil Science › Soil Carbon and Nitrogen Dynamics
Life Sciences › Agricultural and Biological Sciences › Soil Science › Agricultural Science and Fertilization
Physical Sciences › Engineering › Biomedical Engineering › Thermochemical Biomass Conversion Processes
Keywords: biochar, sustainable agriculture, soil carbon sequestration, soil fertility, crop productivity, conservation agriculture, climate change mitigation, food security, soil properties, occupational health and safety, agricultural policy

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Biochar implications for sustainable agriculture and environment: A review

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