Terra preta For newbies

[mjodvis]

I have a couple of questions about terra preta that I'm posting on the newbie site since I definitely fall under that category. Hopefully, neither question is too naïve. My apologies if these questions have been answered elsewhere.

1. I've read numerous places about the remarkable (indefinite?) amount of time that charcoal will remain sequestered in the soil, continuing to replenish soil nutrients with microbial help. This got me thinking about the effects that earthworms might have on the amount of charcoal in the soil. Are there any data on earthworm consumption of charcoal in the soil? And, if so, does the charcoal become something else after passing through an earthworm, or is it still charcoal?

2. On another terra preta thread I read about how the pottery shards in the soil appeared to be made with a type of sponge that provided the pottery with tiny silica tubes or microfilaments that enhanced certain kinds of microbial activity (that was my understanding of it at least.) Have there been any studies on attempting to use plants with a high silica content, such as horsetails (equisetum), as a source of biochar or compost in modern terra preta experiments? I imagine that the silica in such plants would not be in the correct microtubule form, but then again, my knowledge of biochemistry is pretty minimal.

Thanks for any elucidation.

mjodvis

[erics2112]

I've got a friend looking for a pyrolysis unit to produce agrichar to replace his current stove that he uses to heat a greenhouse. Where can one be found? Or plans for building one?

TIA - Eric

[Philip Small]

Originally Posted by erics2112

I've got a friend looking for a pyrolysis unit to produce agrichar to replace his current stove that he uses to heat a greenhouse. Where can one be found? Or plans for building one?

TIA - Eric

I believe the solution is simply an airtight stove with either a catalytic converter or an optimized design.

An airtight stove restricts airflow sufficiently to support pyrolysis. It will have a sealed firebox and tight fitting door. It will have a manually operated or thermostatically controlled air-intake damper to allow air to circulate around the firebox and to control the rate of fuel consumption. It provides slow-burning heat for a long period with relatively little attention. Shutdown before the burn is complete will yield charcoal.

Because the airtight stove is slow burning, it may not ignite the wood gas generated. Air tight stoves have a reputation of sometimes causing heavy creosote buildup in the chimney and pipes. This leads to chimney fires, which btw are incredible: very impressive roar, extremely hot, shooting flames, and very intimidating. Keep a chimney fire extinguisher handy if you use an airtight stove. Chimney brushes or soot removers are normally relied upon to solve this problem. A solution that adds US$2-400 is a catalytic converter in front of the flue. This pdf has a good schematic on the last page. Be aware that these converters are susceptible to fouling and even with good care, won't last forever.

I had a housemate (1978) who constructed an airtight stove out of 0.25 inch plate steel that got around the creosote problem, and without using a catalytic converter. It produced charcoal - I wish we still had it. He designed it so that a horizontal baffle directed the wood gas away from the flue and past the air intake. This provided enough oxygen to mostly ignite the smoke, creating a marginal afterburner effect, sufficient to make the creosote problem more manageable.

The wide stove front was almost completely covered by a pair of doors for loading fuel, the flat steel provided a decent seal. The flue was off the top, back and to the right. The air intake was centered low on the left side and wan controlled by a "kick spin plate", a large round steel cover welded to a bolt threaded into the stove body, centered on the intake vent. You wore thick boots to spin it, thus the name. The baffle was the key, and my mate went through several iterations before he final welded the deal. First he had to put in a gated bypass damper in the baffle, placed under the flue - otherwise there was insufficient initial draft to start the fire and reloading would smoke out the house. The bypass was operated by an L-terminated rod projected out the right side of the stove. Then he put in a U-shaped cut-out in the left edge of the baffle where it lined up with the air-intake. This was needed to ease constricted airflow. In retrospect, he wished he had either added a second, afterburner air intake, or had simply bumped the air intake up higher, off the base plate and closer to the baffle. As it was, air supporting the afterburner effect also tended reduce the pyrolysis effect.

The final trick with this stove was arranging the fuel. A big horking air-diverting piece of wood went on the air intake side of the fuel placed under the flue. This seemed essential to get a fast start and an even burn. Perhaps if the air intake had been higher this wouldn't have been essential.

A neat feature with the stove is you could operate it with the huge front doors open (baffle bypass open) for short cheery runs. Nice option to have at times.

[Winkelix]

I just had a question about terra preta and cold climates. I know that in the Amazon it has been used. But I couldn't find anything about use in cold climates, such as Canada. I understand that special bacteria in the soil co-exist with the charcoal and slowly release nutrients. But does this work in cold climates? I was thinking maybe the bacteria are sensitive to cold and don't survive to well in a place like Canada.

[freeztar]

Originally Posted by Winkelix

I just had a question about terra preta and cold climates. I know that in the Amazon it has been used. But I couldn't find anything about use in cold climates, such as Canada. I understand that special bacteria in the soil co-exist with the charcoal and slowly release nutrients. But does this work in cold climates? I was thinking maybe the bacteria are sensitive to cold and don't survive to well in a place like Canada.

Good question!

The "wee-beasties" (microbial life in soil) in Terra Preta (TP) is specific to that region and climate.
Here in Georgia, we have a sub-tropical climate and perhaps some of the wee-beasties found in TP can be found in properly prepared soils here. Of course, some will not and other ones (more suited to this climate) will take the place, I think.

The abundance of life in Canada (most parts) suggests to me that wee-beasties specific to the regions and climates would be present in the soil. The question then becomes, "What is the relative effectiveness of TP synthesis in colder climates compared to traditional, tropical TP soils?".

An important thing to consider is that during summer (the growing season), temperatures rise, which gives life to dormant soil inhabitants. Unfortunately I've not come across an article dealing with this question.

Perhaps others will chime in.

[Philip Small]

Originally Posted by freeztar

The abundance of life in Canada (most parts) suggests to me that wee-beasties specific to the regions and climates would be present in the soil. The question then becomes, "What is the relative effectiveness of TP synthesis in colder climates compared to traditional, tropical TP soils?".

An important thing to consider is that during summer (the growing season), temperatures rise, which gives life to dormant soil inhabitants. Unfortunately I've not come across an article dealing with this question.

Perhaps others will chime in.

Most chars have a liming effect which can bring about dramatic changes in acid soil settings. Bacteria in particular appreciate the rise in pH. Alfalfa/lucerne and wheat can be very responsive to liming.

I'll hazard a guess that char-adapted fungi, bacteria, and archaea should be present in all but the most distressed soil. For those cases a biofertilizer approach is a reasonable tactic, ala Jeff Lowenfels' "Teaming With Microbes" (Recommended). You could inoculate a charcoal dominated compost pile with good soil to produce the biofertilizer needed for the distressed soil.

There will be differences between species in response to added char, but they should be in residence because soils generally contain charcoal, at least in settings which retain surface soils with a prolonged fire history.

From http://soil.scijournals.org/cgi/reprint/66/4/1249.pdf

High levels of charcoal C resulting from repeated historical burning of grasslands, open woodlands, and agricultural crop residues have been reported in soils from Australia and Germany. In this study, five U.S. soils were selected from long-term research plots in widely different agricultural areas. The charcoal C content was estimated...

These analyses showed that all five soils contained measurable amounts of charcoal C ... [which] constituted up to 35% of the soil total organic C (TOC).

The authors mention a similar high of 30% in Australia. Sad thing is that tillage seems to be responsible for increasing the Char-C% of TOC. The tillage oxidating influence has more effect on the less recalcitrant bits.

In Canada, the sweet spot for the desired response to charcoal may well be with smaller, incremental additions simply because the resident microbial community may be set back by single, large additions of new char. The liming potential of charcoal is a factor in this. Fungi can do some amazing things for soil quality. Where fungi species are significant to soil character, a reasonable scenario in Canada, jumping the pH up a click by incorporating 20 tonnes/ha charcoal is not necessarily the best option. Unless we're trying to grow copious amounts of lucerne, in which case jumping the pH up to just below neutral is hard to find fault with.

Soil, and simple. Not often used in the same sentence.

[Winkelix]

Thanks for that
I have another question about this.
Say I was to add a bunch of charcoal to a garden (assuming is works in a cold climate), how long would it take for any positive effects to take place? I read somewhere that it takes a few years for it to start working. I was just wondering whether any of you know about it, because I might try it on a garden, just to see how it works.

[Philip Small]

Originally Posted by Winkelix

...how long would it take for any positive effects to take place?

You could band seed with fine char and fertilizer. With a control to compare results against, you coukd determine if short term effects are happening. Banding char with wheat and fertilizer in Australia works the same season. You can also do comparative potted plant studies for a high degree of control. An outdoor native tree and shrub nursery has been using char as a carrier for biofertilizer at planting time, which makes good sense to me. My guess is that fairly immediate effects can be achieved in most circumstances, but it may take a few runs to figure out what actually works.

[DougF]

I just had a question about Terra Preta and the amount of char in a sandy soil?
I live in Florida and the soil is very sandy here I was thinking of putting char on my lawn, will this work here and how much should I use? I'm very new to this so if can help I would appreciate it, thanks DougF

[Philip Small]

Originally Posted by DougF

I live in Florida and the soil is very sandy here I was thinking of putting char on my lawn, will this work here and how much should I use?

I hope it will work because I am going to try it on my rocky sandy shallow soiled lawn. Planning to crush up some char and apply with my neighbors push-along fertilizer spreader. Going to hit the parts that cook in the sun the most. Hoping to start bumping up the water holding capacity, get a tad of a mulching effect, and boost the near surface microbial community. An aside, I find that mowing higher helps: drives the grass rooting depth deeper, keeps the crown a tad cooler/moister. Long term plan for the current lawned areas is a combo herb garden/thyme lawn - no grass.