Role of biochar in promoting circular economy in the agriculture sector. Part 2: A review of the biochar roles in growing media, composting and as soil amendment

Jindo, Keiji; Sánchez-Monedero, Miguel Angel; Mastrolonardo, Giovanni; Audette, Yuki; Higashikawa, Fábio Satoshi; Silva, Carlos Alberto; Akashi, Kinya; Mondini, Claudio

doi:10.1186/s40538-020-00179-3

Chemical and Biological Technologies in Agriculture

Table 2 Impact of biochar application on main soil properties affecting crop productivity

From: Role of biochar in promoting circular economy in the agriculture sector. Part 2: A review of the biochar roles in growing media, composting and as soil amendment

Property class	Property	Effect	Mechanism/explanation	References
Positive impacts
Physical	Structure	Increased aggregation	Enhanced cohesion by binding of biochar to organo-mineral complexes	[62]
	Porosity	Increase	Porosity of biochar, increased aggregation and reduction of soil packing	[64]
	Density	Decrease	Low density of biochar particles and interaction of biochar with soil increasing aggregation	[63]
	Water-holding capacity	Enhancement	Large specific surface area and porosity of biochar	[63]
	Infiltration rate	Increase	Increase in pore space and water flow by mixing of large biochar particles with smaller soil inorganic particles	[63]
	Colour	Dark colour	Alteration of thermal dynamics that favours rapid germination	[66]
Chemical	Soil organic matter	Increase	Input of highly recalcitrant C	[57]
	Element cycling	Regular functioning	Increase in the pool size and turnover of labile organic nutrients, surface adsorption and effects on soil biota	[65]
	Nutrient availability	Enhancement	Direct supply of nutrients surface adsorption of elements	[54, 67]
	Cation exchange capacity	Enhancement	Porous structure, large and mainly negative surface area of biochar. Adsorption of highly oxidized organic matter on biochar surfaces. Biotic and abiotic oxidation of biochar organic functional group	[65]
	pH	Increase	Biochar alkalinity, high pH buffer capacity, biochar functional groups	[64]
Biological	Soil habitat	Refuge of microorganisms against predators	Biochar pores fits microorganisms but not micro-arthropods predators	[64]
	Microorganism abundance	Increase in microbial biomass	Biochar improvements to soil habitat, bulk density, pH and elements and water cycling	[51]
	Microorganism diversity	Increased abundance of bacteria over fungi	Modification in the c/n ratio of readily mineralizable substrate	[62]
	Microorganism activity	Increase in Co₂ and enzyme activity	Degradation of available substrates from biochar	[76]
	Plant growth	Increase in root biomass	Increase in the content of plant growth-promoting hormones	[68]
	Plant disease resistance	Induction of systemic resistance	Input of chemical elicitors	[69]
Negative impacts
Chemical	Nutrients (P, N, Fe, B)	Immobilization	Excessive alkalinity	[58]
	N availability	Decrease	Microbial N immobilization	[67]
	Heavy metal and metalloids	Enhanced mobility	Excessive pH increase	[71]
Biological	Microbial and plant activity	Decline	Excessive content of toxic substances	[58]

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