The Benefits of Charcoal in the Soil (Research Links)

Charcoal produced at exothermic range of temperatures, has a chemical structure with significantly less available carbon for microbial action.  However, the char structure of biomass appears to to provide safe haven to microbial communities (Pietikäinen) and increase nutrient availability.


  1. Selections from: Soil microbes in boreal forest humus after fire
  2. The nature of unextractable organic matter fractions in allophanic andosols

  3. The charcoal effect in Boreal forests: mechanisms and ecological consequences

  4. Nitrogen mineralization and phenol accumulation along a fire chronosequence in northern Sweden
  5. The 'Terra Preta' phenomenon: a model for sustainable agriculture in the humid tropics
  6. Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal - a review
  7. Method describing the use of rice hull ash and expected crop benefits
  8. The use of charcoal and rhizobia to stimulate nutrient uptake
  9. Selected information on effects of using charcoal as a soil amendment
  10. (selected text) Potential of Pyrolyzed Organic Matter in Soil Amelioration


1. Selections from: Soil microbes in boreal forest humus after fire

Surprisingly, the ecological significance of charcoal lay in the fact that the charcoal itself supported a microbial community which was small but more active than that of the humus. When all the adsorbents were provided with similar environmental conditions and substrate, it was found that the size and structure of the microbial community depended on the properties of the adsorbent. After the one-month incubation, the size of the microbial biomass in the adsorbents followed the order EmpCh > HuCh > ActC > Pum (V, Fig. 1). Activity, measured as basal respiration and rate of bacterial growth rate, were higher in both charcoals than in ActC or Pum. The specific growth rate, i.e. growth per bacterial cell, did not differ significantly between adsorbents, although the microbial communities established in the adsorbents differed with respect to their PLFA and their substrate utilisation patterns. Microbial communities of ActC and EmpCh resembled each other with regard to their PLFA patterns, while the community in Pum clearly differed from the first group (V, Fig. 3). Obviously, the microbes attached themselves to charcoal (or activated carbon) particles and degraded the adsorbed substrates like in biological activated carbon beds (De Laat et al. 1985, Kim et al. 1997). In conclusion, when moistened with substrate-rich litter extract, the charcoal formed by combustion was capable of supporting microbial communities.

The results of this microcosm study indicate that charcoal has the potential to support microbial communities. However, this does not imply that the same would also be true in the field; but the presence of microbial communities in the charcoal layer should be studied after a fire in natural conditions. Conditions similar to those simulated in the microcosms might be expected to occur from two years after burning onwards, when pioneer vegetation has covered the burned area and produces abundant litter. Charcoal might also be favoured by soil microbes because, as suggested by Zackrisson et al. (1996), the micropore structure of charcoal could shelter microbes against predators.

http://ethesis.helsinki.fi/julkaisut/maa/mekol/vk/pietikainen/soilmicr.html     TOP

2. The nature of unextractable organic matter fractions in allophanic andosols

Up to 50% of the organic matter in most soils is unextractable by standard methods. This unextractable matter contains undecomposed plant remains, remnants of apolar aliphatic polymers, charcoal, and strongly mineral-bound matter. In the light of global carbon dynamics, the very strongly bound fraction, which is very stable over time, is extremely important. This project aims to characterize this fraction. It is isolated through various extraction procedures. Characterization is by pyrolysis-GC/MS or equivalent methods.

http://www.dow.wageningen-ur.nl/ssg/educat/tsr1-6.htm      TOP

3.The charcoal effect in Boreal forests: mechanisms and ecological consequences

Abstract Wildfire is the principal disturbance regime in northern Boreal forests, where it has important rejuvenating effects on soil properties and encourages tree seedling regeneration and growth. One possible agent of this rejuvenation is fire-produced charcoal, which adsorbs secondary metabolites such as humus phenolics produced by ericaceous vegetation in the absence of fire, which retard nutrient cycling and tree seedling growth. We investigated short-term ecological effects of charcoal on the Boreal forest plant-soil system in a glasshouse experiment by planting seedlings of Betula pendula and Pinus sylvestris in each of three humus substrates with and without charcoal, and with and without phenol-rich Vaccinium myrtillus litter. These three substrates were from: (1) a high-productivity site with herbaceous ground vegetation; (2) a site of intermediate productivity dominated by ericaceous ground vegetation; and (3) an unproductive site dominated by Cladina spp. Growth of B. pendula was stimulated by charcoal addition and retarded by litter addition in the ericaceous substrate (but not in the other two), presumably because of the high levels of phenolics present in that substrate. Growth of P. sylvestris, which was less sensitive to substrate origin than was B. pendula, was unresponsive to charcoal. Charcoal addition enhanced seedling shoot to root ratios of both tree species, but again only for the ericaceous substrate. This response is indicative of greater N uptake and greater efficiency of nutrient uptake (and presumably less binding of nutrients by phenolics) in the presence of charcoal. These effects were especially pronounced for B. pendula, which took up 6.22 times more nitrogen when charcoal was added. Charcoal had no effect on the competitive balance between B. pendula and P. sylvestris, probably due to the low intensity of competition present. Juvenile mosses and ferns growing in the pots were extremely responsive to charcoal for all sites; fern prothalli were entirely absent in the ericaceous substrate unless charcoal was also present. Charcoal stimulated active soil microbial biomass in some instances, and also exerted significant although idiosyncratic effects on decomposition of the added litter. Our results provide clear evidence that immediately after wildfire fresh charcoal can have important effects in Boreal forest ecosystems dominated by ericaceous dwarf shrubs, and this is likely to provide a major contribution to the rejuvenating effects of wildfire on forest ecosystems.

D. A. Wardle, O. Zackrisson, M.-C. Nilsson    Department of Forest Vegetation Ecology, Swedish University of Agricultural Sciences, Faculty of Forestry, S-901 83 Umeå, Sweden

 http://link.springer-ny.com/link/service/journals/00442/bibs/8115003/81150419.htm       TOP

4. Nitrogen mineralization and phenol accumulation along a fire chronosequence in northern Sweden

Abstract. Scots pine (Pinus sylvestris L.) forests of northern Sweden are often considered to be N limited. This limitation may have been exacerbated by the elimination of wildfire as a natural disturbance factor in these boreal forests. Phenolic inhibition of N mineralization and nitrification (due to litter and exudates of ericaceous shrubs) has been proposed as a mechanism for N limitation of these forests, but this hypothesis remains largely untested. N mineralization rates, nitrification rates, and sorption of free phenolic compounds were assessed along a fire-induced chronosequence in northern Sweden. A total of 34 forest stands varying in age since the last fire were identified and characterized. Overstorey and understorey vegetative composition and depth of humus were analysed in replicated plots at all 34 sites. Eight of the forest stands aged 3-352 years since the last fire were selected for intensive investigation in which ten replicate ionic resin capsules (used to assess net N mineralization and nitrification) and non-ionic carbonaceous resin capsules (used to assess free phenolic compounds) were installed at the interface of humus and mineral soil. A highly significant correlation was observed between site age and net sorption of inorganic N to resin capsules. Net accumulation of NH4+ and NO3- on resin capsules followed a linear decrease (R2=0.61, P<0.01) with time perhaps as a result of increased N immobilization with successional C loading. NO3- sorption to resin capsules followed a logarithmic decrease (R2=0.80, P<0.01) that may be related to a logarithmic increase in dwarf shrub cover and decreased soil charcoal sorption potential along this chronosequence. A replicated field study was conducted at one of the late successional field sites to assess the influence of charcoal and an added labile N source on N turnover. Three rates of charcoal (0, 100, and 1,000 g M-2) and two rates of glycine (0 and 50 g N as glycine M-2) were applied in a factorial design to microplots in a randomized complete block pattern. Net ammonification (as assessed by NH4+ sorption to resins) was readily increased by the addition of a labile N source, but this increase in NH4+ did not stimulate nitrification. Nitrification was stimulated slightly by the addition of charcoal resulting in similar levels of resin-sorbed NO3- as those found in early successional sites. Resin-sorbed polyphenol concentrations were decreased with charcoal amendments, but were actually increased with N amendments (likely due to decomposition of polyphenols). Net N mineralization appears to be limited by rapid NH4+ immobilization whereas nitrification is limited by the lack of an appropriate environment or by the presence of inhibitory compounds in late successional forests of northern Sweden.

DeLuca, Nilsson, and Zackrisson (2002), Oecologia 133: 206-214 http://link.springer.de/link/service/journals/00442/contents/02/01025/s00442-002-1025-2ch002.html     TOP

5. The 'Terra Preta' phenomenon: a model for sustainable agriculture in the humid tropics

Abstract. Many soils of the lowland humid tropics are thought to be too infertile to support sustainable agriculture. However, there is strong evidence that permanent or semi-permanent agriculture can itself create sustainably fertile soils known as 'Terra Preta' soils. These soils not only contain higher concentrations of nutrients such as nitrogen, phosphorus, potassium and calcium, but also greater amounts of stable soil organic matter. Frequent findings of charcoal and highly aromatic humic substances suggest that residues of incomplete combustion of organic material (black carbon) are a key factor in the persistence of soil organic matter in these soils. Our investigations showed that 'Terra Preta' soils contained up to 70 times more black carbon than the surrounding soils. Due to its polycyclic aromatic structure, black carbon is chemically and microbially stable and persists in the environment over centuries. Oxidation during this time produces carboxylic groups on the edges of the aromatic backbone, which increases its nutrient-holding capacity. We conclude that black carbon can act as a significant carbon sink and is a key factor for sustainable and fertile soils, especially in the humid tropics.  


Glaser, Haumaier, Guggenberger and Zech (2001) Naturwissenschaften 88: 37-41 http://link.springer.de/link/service/journals/00114/contents/00/00193/s001140000193ch002.html   TOP

6.  Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal - a review

Abstract. Rapid turnover of organic matter leads to a low efficiency of organic fertilizers applied to increase and sequester C in soils of the humid tropics. Charcoal was reported to be responsible for high soil organic matter contents and soil fertility of anthropogenic soils (Terra Preta) found in central Amazonia. Therefore, we reviewed the available information about the physical and chemical properties of charcoal as affected by different combustion procedures, and the effects of its application in agricultural fields on nutrient retention and crop production. Higher nutrient retention and nutrient availability were found after charcoal additions to soil, related to higher exchange capacity, surface area and direct nutrient additions. Higher charring temperatures generally improved exchange properties and surface area of the charcoal. Additionally, charcoal is relatively recalcitrant and can therefore be used as a long-term sink for atmospheric CO2. Several aspects of a charcoal management system remain unclear, such as the role of microorganisms in oxidizing charcoal surfaces and releasing nutrients and the possibilities to improve charcoal properties during production under field conditions. Several research needs were identified, such as field testing of charcoal production in tropical agroecosystems, the investigation of surface properties of the carbonized materials in the soil environment, and the evaluation of the agronomic and economic effectiveness of soil management with charcoal.

Glaser, Lehmann and Zech  (2002) Biol Fertil Soils 35: 219-230 http://link.springer-ny.com/link/service/journals/00374/contents/02/00466/s00374-002-0466-4ch002.html  TOP


This technology is best suited to small-scale farming, and to sandy, acidic and relatively infertile soils. It is effective for such crops as soybean, cowpea, corn and sorghum. It is also worth trying for other field crops and vegetables.



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Cooperating agency for this topic: Association for International Cooperation in Agriculture and Forestry, Japan 19, Ichiban-cho, Chiyoda-ku, 102-0082 Japan

PDF Document

http://www.agnet.org/library/article/pt2001004.html   TOP

8. Utilization of Indigenous AMF by the Application of Charcoal

(selected paragraph) The idea that the application of charcoal stimulates indigenous arbuscular mycorrhizal fungi (AMF) in soil and thus promotes plant growth is relatively well-known in Japan, although the actual application of charcoal is limited due to its high cost. The concept originated in the work of M. Ogawa, a former soil microbiologist in the Forestry and Forest Products Research Institute in Tsukuba. He and his colleagues applied charcoal around the roots of pine trees growing by the seashore, and found that Japanese truffles became plentiful. He also tested the application of charcoal to soybean with a small quantity of applied fertilizer, and demonstrated the stimulation of plant growth and nodule formation (Ogawa 1983). His findings with regard to legumes were taken up for further study by the National Grassland Research Institute (Nishio and Okano 1991). 

Stimulation of Nutrient Uptake by Charcoal Application

The amount of nutrients (N, P, K) absorbed by the shoots showed a trend similar to that of the shoot fresh weight (Table 1). The amount of N fixed by the nodules and transported to the shoots was calculated by subtracting the N content of the shoots of the plants not inoculated with rhizobia from the N content of the inoculated plants ([F+R]-[F], [F+R+C] - [F+C]). The addition of charcoal increased this amount of N 2.8-4.0 times, and the ARA by 6.2 times (Table 2). Added charcoal also increased the nodule weight by 2.3 times.

PDF Version

Michinori Nishio, (1999) National Institute of Agro-Environmental Sciences - Japan

http://www.agnet.org/library/article/eb430.html#2    TOP

9. Selected information on effects of using charcoal as a soil amendment

Growth and Harvest of Soybeans

ITEM Areas Not Using Charcoal Areas Using Charcoal for Compost Areas Using Chemical fertilizer
No. of leaves 64 139 71
Avg. Leaf Length 5.76 7.68 6.04
Avg. of Leaf Width 3.25 4.08 3.26
Germination Rate (%) 80 90 85
Root Length 22 24 25.5
Stem Length 14.66 17.19 18.23
Stem Diameter 1.2 1.35 1.33
No. of Seeds 26 89 37
Weight of 100 Seeds 28.1 44.25 33.85

Utilization Experiment of Charcoal Tested in Indonesia
Data Provided by the Japanese Forestry Agency
All measurements are in centimeters.

http://www.murayoshi.com/en/practical.html   TOP

10. (selected text) Potential of Pyrolyzed Organic Matter in Soil Amelioration

12th ISCO Conference, May 26-31, 2002. Beijing, China, (Proceedings, Vol III, p421) Bruno Glaser , Johannes Lehmann , Christoph Steiner , Thomas Nehls , Muhammad Yousaf and Wolfgang Zech

(selection snipped)

The potential of Cpyr to increase crop yields

We investigated whether charcoal additions to highly weathered Ferralsols could increase plant growth. For this aim, three bioassays were done using cowpea (Vigna unguiculata), rice (Oryza sativa) and oats (Avena sativa) as test plants. For the first experiment, mineral fertilizer was compared to manure and charcoal applications on a Xanthic Ferralsol and a Fimic Anthrosol (Terra Preta) in Central Amazonia. The Anthrosol was a relict soil from pre-Columbian settlements with high organic C containing large proportions of black carbon. Only the Ferralsol received 10 % and 20 % (w/w) charcoal (67.6 and 135.2 Mg C ha –1 , respectively), which was produced by local farmers originating from secondary forests. The applied amounts of charcoal at 10 % were in the range of projected charcoal yields from the wood biomass of Amazonian forests (Fearnside et al., 1999; Fearnside et al., 1993) which calculate to 57—66 Mg C ha –1 for the topsoil (0m—0.1m) with an estimated mass loss of 70 % during charcoal production 74.8 % from (Correa, 1988). Charcoal additions increased biomass production of a rice crop by 17% in comparison to a control on a Xanthic Ferralsol (Fig. 3) which was shown to be largely an effect of improved P, K, and possibly Cu nutrition (Lehmann et al., 2002b). Increasing the amount of charcoal further increased above-and belowground biomass production (Fig. 4).

Fig.3 Biomass production of rice (Oryza sativa) after additions of charcoal and fertilizer to a Xanthic Ferralsol or a Fimic Anthrosol after 37 days in a greenhouse experiment at 28°C—32°C and 2,500 mm precipitation per year (means and standard errors; N=4; Lehmann et al., 2002a)

Entire article (mirrored)

http://www.tucson.ars.ag.gov/isco/isco12/VolumeIII/PotentialofPyrolyzedOrganic.pdf   TOP