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ideas ready to be refuted - step right up
Hello all, apologies for starting a brand new thread again, but I really hate tacking a long post with lots of questions onto the end of a different thread that no-one's reading (and this is a lonnnng post - sorry in advance). That said though, if a moderator wishes to move this this they're more than welcome.
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So then, I've become a bit obsessed with this tp thing since I discovered it at the weekend, and I've drawn my own conclusions that go against the prevailing opinion regarding tp. Now, if a neophyte like me comes into the fray with new ideas based on very little knowledge, they're almost certainly wrong and ill informed, which is why I'd really like to hear some peoples opinions
Here's my two conclusions so far:
1 - terra preta was created all in one go, by people who knew what they were doing and had done it many times before.
2 - the actual process of terra preta is rather more simple than many believe, but depth is critical
I believe 1 to be true because of the pot sherds, and I explained that in a post a few days ago so I won't bore you further by repeating it here except to summarise it: I think the pot sherds were placed flat deliberately while the soil was being built in order to slow the progress of water through the soil and give more contact with charcoal.
I believe 2 to be true in great part because of my belief in 1. I don't believe it was done over many decades/centuries. I don't believe you can turn barren soil into tp with the application of a small amout of charcoal tilled into the topsoil, and equally, if you could, why would they have continued to build up the layers with time? If I had inexhaustible, regenerative tp in my garden right now, I wouldn't keep adding charcoal to it. In effect, what I believe is that the charcoal, as is well established, "filters" the rain water and prevents leaching, meaning whatever organic material and other nutrients that go into the soil don't come out the bottom. All gardeners know what happens when you heavily water a pot containing a bit of manure - the water that comes out the bottom is brown and you see all the precious goodness flowing away. The charcoal stops this, but ONLY (in my opinion) in proportion to the depth.
No doubt this is all sounding very simplistic, but bare with me because it's about to get worse. I'm not convinced that the temperature at which the charcoal is formed, nor the materials it's made from, is particularly important. It may be that low temperature charcoal works better, but I would say that 1 foot of perfectly cooked charcoal is not going to be as good as 1 meter of bad charcoal. Depth is the key - if there's one thing I've learned about gardening it's that you can't do it down a microscope. It seems to me that tp is little more than a massive water filter, and if so can be reproduced anywhere with fairly similar results. All you need is enough charcoal. The effect of the pot shards, in my opinion (I'll stop saying this from now on, it's very annoying), acts only to reduce the depth of charcoal needed, and could be replicated with any impervious material, though I don't doubt that terracotta is also is a great refuge for little beasties in the soil.
However, as stated, this is all contrary to the general thinking on tp, so I'd be very interested to hear why I'm wrong. With that in mind, I have some specific questions that I'd like answered:
1 - How do we know they charred food, leaves and other waste products as is often suggested, rather than just wood?
2 - What evidence is there that these soils were built over a great deal of time that I may have missed?
3 - what is the evidence that the soil regenerates apart from what the farmers say? Photos?
4 - what experimental/anectdotal evidence do we have about removing tp from its surroundings?
Regarding 1 and 2, I'd really like some specific, scientifically tested results, not just what seems to be scientific speculation repeated as fact by journalists.
Regarding question 3 - I'm not really convinced about this whole regeneration thing. Has anyone done any experiments? Not that I'm doubting the people who say it appears to grow back, but I think the word "regenerate" is a bit misleading. It clearly doesn't "grow" outwards, else the world would be covered in it, and equally, if it "grows" upwards then the areas of terra preta that are thousands of years old should be hundreds of meters high by now. I don't believe it grows at all, and I don't believe it's as inexhaustible as people think - I'm more inclined to believe it's just got a hefty storage capacity. An additional question on this would be: if they harvest the terra preta with pot shards in it, does the new stuff grow back without potshards, or are the potshards from below moved up over time? How is the "regenerated" tp different? Presumably the percentage of carbon is less?
Regarding question 4 - we know terra preta is being bagged and sold in brazil, but it's damn hard to find info about anyone using it. We know it grows nice flowers at the airport, but what else is there? Surely people have done the obvious and tested it out in different amounts and depths? My hunch, again, is that as soon as you start to reduce the depth, the effects diminish - I don't believe there's any "magic" going on here, and I'm not convinced on the specialized microbes line of thinking either.
So, what have we learned so far then, apart from the fact that I'm developing a slightly unhealthy obsession? Well, to summarise my theory, I believe depth of charcoal is the one critical factor that everyone seems to be ignoring. I've seen so many theories put forward about how it's formed and how to make it, and many far fetched ideas, but nothing so far that treats the depth (and the "slowing" effect of the pot sherds) as important. One of the reasons for that is the simple fact that, lets face it, making charcoal is a pain in the arse. It's slow, messy, uses lots of fuel, has to be watched for a long time and at the end of it all has to be crushed up. Therefore, I think the people who are adding charcoal to the soil are simply not adding enough at a great enough depth. At the other end of the scale, people who are buying the stuff can't afford to buy it by the truckload and then dig it down to two meters depth. After all, as a couple of people on here have pointed out, crop roots only go down a foot or so, so why would you need charcoal any deeper? That's a sensible question, but unfortunately soil doesn't work like that. I expect most people here have heard of the deep bed method, and certainly you are all aware of the problem of compaction in soil. The point is, even though the crop roots only go down a foot or so (though often much much more, especially when using a deep bed no till system), the entire soil is alive and organic matter and nutrients are constantly moving, right down to the subsoil and beyond.
Sorry, I'm digressing again, I should get to the point here. I'm going to do a little experiment on a small patch of land. I'm going to dig down to a depth of at least a meter and a half, and then fill it back up in the way I think the original tp people did - i.e. with a heck of a lot of charcoal, some manure to activate it, soil, bits of pan tile laid flat, and probably a few other things I've forgetten. For the charcoal, to make things a bit easier, I'm going to cheat by using something I haven't yet seen discussed anywhere - namely sawdust. Now I certainly don't think the indians ever had access to a friendly carpinter with a bandsaw, and I'm sure that the effect of charring large lumps of wood is very different to wood dust, but I'm trying to make things easy enough that I don't get bored of it and give up half way. I experimented last night with charring sawdust in a fire and the results were spectacular - a beautiful fluffy pitch black material. Plus, because the sawdust was so fine I didn't even need to seal the top (though the top went to ash, the rest was fine). For a test I put a tiny amount in a pot and then urinated in it, and it's sitting here right now on my desk (I'm not married) and doesn't smell in the slightest. Quite astonishing. I've been humanuring for a few months with sawdust, and had I used the same ratio of urine to sawdust rather than charcoal it would stink to high heaven. It's basically 95% urine, with bits of dust floating in it, yet even after 24 hours I can't smell a thing. Remarkable.
OK, so I think that's it. I have dozens of other questions that I haven't made explicit here, so please jump in if you see that I'm way off in any of my thinking. Oh, I have one other question that I would love a definite answer to - what's the big deal about using plywood/chipboard in the charcoal? The carpenter I got the sawdust from mostly uses untreated woods, but also various pressure treated stuff on occasion. I can understand why this would not be wanted in humanure, since despite the astonishing "eating" power of thermophillic bacteria, you really don't want chemicals designed to stop bacterial growth sitting in your topsoil, but is that really such an issue if it's been charred?
If you've read this far, I apologise for my obvious incapacity to keep to the point when I'm excited about something.
Gaudencio
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