“Biochar” has specific characteristics (i.e.”micropores”) that appear to be quite useful for soils (and Soil Organisms and Nutrient Cycling) that only appear when biomass (i.e. clean, woody plant matter) is Pyrolyzed (or gasified).
Up close, biochar looks something like this under a microscope [the one of the far right]:
This micro-porous structure comes as a result of the “vascular” structure of plant cells in the original biomass:
Soil Bacteria, Actinomycetes, and Fungi — including Mycorrhizae — tend to really like the ‘micro habitats’* that Biochar creates, especially if the biochar is “inoculated”, i.e. if the Biochar is mixed in with healthy soil (that already has mycelia), or if the biochar is co-composted (along with wet “green waste” — from harvest residuals).
Note: It is not recommended that biochar be inoculated with urban-derived mixed compost since there may be too much salt content, which may hinder plant growth and inhibit micro-organism interactions with the biochar.
Of course, one can also apply additions of other things like urea, molasses, and perhaps even “rock dust” (or “pottery shards”) to provide even more beneficial ‘food’ for the microorganisms that are living in all soils.
* Some biochar practitioners have also indicated that biochar has a structure that serves a function similar to that of a “coral reef” in the ocean… but for the soil. Although rarely captured (on film), it is suspected that the intricate, complex structures and high ‘surface area’ tends to create a lot of “hiding places” for the soil micro-organisms, which will interact with both nutrients, minerals, water and other biological residues – as well as with each other.
Root hairs ~ and in particular, the mycelia of Mycorrhizae, do seem to prefer this type of complex “habitat”:
Thus, if you “plant” the char into the root zone along with the crops (and green manures and other ‘organic fertilizers’), biochar seems to be able to accelerate the process of creating amazingly healthy soils.
Without all those little ‘pores’ in the biochar there will be far less water holding capacity (when the soil is dry) … as well as fewer air-filled pores available (when the soil is wet).
Anytime there is low water holding capacity and reduced air-filled pores in a soil, this is symptomatic of a similar condition called “soil compaction”**, where the increased bulk density of the soil causes poor soil structure, which means that it becomes more difficult for plants – or any living things – to survive.
Compaction is caused by the cohesion of clay particles, and can prevent plant roots from being able to penetrate into soil layers that may otherwise contain available water, causing stress on the plants.
Compaction can sometimes be quite severe in cities and other urban areas, thus biochar is likely to be quite useful in urban soils, as well as in any other soils where compaction is an issue, since biochar should also be able to loosen the texture of soils and prevent severe compaction, even in “high traffic” areas.
Char acts more like sand than clay in this respect [it has very poor cohesion], however, unlike sand, which has a very low surface area, biochar has a relatively high surface area, which is more like clay.
Thank you for reading “Biochar 101”. Of course there is much more to biochar than this… but it’s a start.
© 2013 Lloyd Helferty, Biochar Consulting