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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Cation exchange, pH and soil solution chemistry / Biochar and charcoal in soil

Biochar and charcoal in soil

How biochar and charcoal persist in soil, change pH, water and nutrient retention, and affect microbes and carbon storage.

Boundary: where this process starts

Starts with: Pyrolysis or wildfire turns biomass into aromatic carbon charcoal

Boundary: where it ends

Ends after: Soil and char type decide the response; Pores shelter microbes and N2O emission falls

PARTICIPANTSRESOURCESBiocharSoil microbesPlant rootsFireSoil solutionCarbonBiocharWaterHydrogen ionsPlant litterImpact +3 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.40% acidic or infertile soilImpact +3 of 5. Click for details and evidence.25% sandy soilImpact 01 of 5. Click for details and evidence.35% fertile, neutral soilImpact +2 of 5. Click for details and evidence.Impact +2 of 5. Click for details and evidence.↻ reinforces · weak · 0.15Impact -1 of 5. Click for details and evidence.Impact -1 of 5. Click for details and evidence.↻ balances · weak · 0.1Impact +3 of 5. Click for details and evidence.Impact -1 of 5. Click for details and evidence.Pyrolysis or wildfire turns biomass into aromatic carbon charcoal: makes CarbonmakesPyrolysis or wildfire turns biomass into aromatic carbon charcoal: makes BiocharmakesPyrolysis or wildfire turns biomass into aromatic carbon charcoal: uses up Plant litteruses upCharcoal resists decomposition for centuries: uses CarbonCharcoal resists decomposition for centuries: uses BiocharSurface oxidises, gaining carboxyl groups and CEC; pores adsorb water and nutrients: uses WaterSoil and char type decide the response: uses Hydrogen ionsAsh carbonates raise pH and reduce Aluminum toxicity: uses up Hydrogen ionsuses upLower bulk density and higher water holding in sandy soil: uses Waterconverted to aromaticcarbonCarbon: converted to aromatic carbonformed as charcoalBiochar: formed as charcoalpyrolysed or burned intocharPlant litter: pyrolysed or burned into charresists decay forcenturiesCarbon: resists decay for centuriespersists as stablecharcoalBiochar: persists as stable charcoaladsorbed in internalporesWater: adsorbed in internal porescontrol soil acidityresponseHydrogen ions: control soil acidity responseneutralised by ashcarbonatesHydrogen ions: neutralised by ash carbonatesheld more in sandy soilWater: held more in sandy soilStart: Biochar andcharcoal in soilSTARTStart: Biochar and charcoal in soilEnd: Biochar andcharcoal in soilENDEnd: Biochar and charcoal in soilPyrolysis or wildfireturns biomass intoaromatic carb…👍1📄1Pyrolysis or wildfire turns biomass into aromatic carbon charcoalCharcoal resistsdecomposition forcenturies📄1Charcoal resists decomposition for centuriesSurface oxidises,gaining carboxyl groupsand CEC; pores adso…📄1Surface oxidises, gaining carboxyl groups and CEC; pores adsorb water and nutrientsSoil and char typedecide the response📄1Soil and char type decide the responseAsh carbonates raise pHand reduce Aluminumtoxicity📄1Ash carbonates raise pH and reduce Aluminum toxicityLower bulk density andhigher water holding insandy soil📄1Lower bulk density and higher water holding in sandy soilPores shelter microbesand N2O emission falls👍1📄1Pores shelter microbes and N2O emission fallsEarly positive primingof native soil carbon📄1Early positive priming of native soil carbon
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
Participant
Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
Resource
Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
Step
One thing that happens in a process. Every step has at least one participant and carries evidence.
Decision fork
A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
Loop
A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
Size of impact
Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
Evidence
The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
Boundary
Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
Subprocess
A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
Description
A plain-language summary of what a process is and what it covers.
Hypothesis
A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.

Every step, with its evidence

The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.

Pyrolysis or wildfire turns biomass into aromatic carbon charcoal
FireBiocharPlant litterCarbonBiochar
Evidence (1) · added by Fern
  • Lehmann & Joseph 2015, ch. 1: Charcoal is condensed aromatic carbon formed at 350-700 C without oxygen. (confidence 0.65)
Charcoal resists decomposition for centuries
BiocharSoil microbesCarbonBiochar
Evidence (1) · added by Fern
  • Wang, Xiong & Kuzyakov 2016, GCB Bioenergy 8:512: Meta-analysis estimated mean residence time of about 556 years for the stable biochar pool and about 108 days for the labile pool. (confidence 0.6)
Surface oxidises, gaining carboxyl groups and CEC; pores adsorb water and nutrients
BiocharSoil solutionCationsWaterDissolved organic carbon
Evidence (1) · added by Fern
  • Liang et al. 2006, Soil Science Society of America Journal 70:1719: Aged black carbon in Amazonian dark earths had higher CEC per unit carbon than neighbouring soil. (confidence 0.7)
⑂ Soil and char type decide the response
SoilBiocharHydrogen ionsNutrients
Evidence (1) · added by Fern
  • Jeffery et al. 2011, Agriculture, Ecosystems and Environment 144:175: Meta-analysis showed an average 10% productivity increase, largest in acidic and coarse-textured soils. Shares are estimates (+-10 points). (confidence 0.5)
Ash carbonates raise pH and reduce Aluminum toxicity
BiocharAluminumHydrogen ionsAluminumCalcium
Evidence (1) · added by Fern
  • Van Zwieten et al. 2010, Plant and Soil 327:235: Papermill biochar raised soil pH and cut exchangeable Al, improving wheat and radish growth in an acid soil. (confidence 0.7)
Lower bulk density and higher water holding in sandy soil
BiocharSoil poresWaterPore space
Evidence (1) · added by Fern
  • Omondi et al. 2016, Geoderma 274:28: Meta-analysis found biochar lowered bulk density and raised porosity and water holding capacity; effects larger in coarse soils. (confidence 0.6)
Pores shelter microbes and N2O emission falls
Soil microbesDenitrifying bacteriaNitrous oxideNitrate
Evidence (1) · added by Fern
  • Cayuela et al. 2014, Agriculture, Ecosystems and Environment 191:5: Meta-analysis found biochar reduced soil N2O emissions by about 50% on average. (confidence 0.7)
Early positive priming of native soil carbon
Soil microbesBiocharCarbon dioxideSoil organic matter
Evidence (1) · added by Fern
  • Maestrini, Nannipieri & Abiven 2015, GCB Bioenergy 7:577: Meta-analysis found pyrogenic carbon often caused short-term priming, with sign depending on soil and char. (confidence 0.6)