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Posted at 8:19AM on 6 May 07. Permalink.

Fascinating stuff, many thanks. Meanwhile, an interesting piece on a very similar Australian initiative:

http://www.truthout.org/docs_2006/050307R.shtml

Very encouraging to see current Australian of the Year Tim Flannery (__The Future Eaters, The Weather Makers__) giving his support.

Posted at 9:05AM on 6 May 07. Permalink.

Great story- and thanks for the Aussie link, Joe.
I guess you can produce charcoal in vast quantities reasonably cleanly? (Not like the old charcoal works...)
It's interesting to speculate about charcoal, Banks Peninsula and the cocksfoot boom. After indescriminately burning off the bush, the forest soils- presumably somewhat charcoal-enriched- grew remarkable quantites of cockfoot for seed. But the soils were probably already fairly rich, and potash may have been the other factor. And soil depletion- in a fragile environment- started to reduce crops after 30-40 years. So possibly the charcoal was never worked it all.

Posted at 10:38AM on 6 May 07. Permalink.

Rob:

Very interesting about Bank's peninsula. As I understand it, the charcoal has to be worked about 30-40 cm deep for significant effects. Apparently, the soils in the Amazon can have charcoal worked up to 2 metres deep (but presumably that occurred over several generations).

Yes, the new technique for charcoal production is much cleaner and more efficient than previous methods. I'm told that the process is a net energy producer, as opposed to the previous methods which required an energy input. See the information on the energy-efficient production of charcoal at the University of Hawaii.

Joe:

Many thanks for the link to the report on the Australian Agrichar conference. I'll add that to the 'Further reading' section on Public Address Radio.

By the way, I am terribly impressed that you have the Muskrat as your gravatar. I hope you don't have mysterious forebodings too often...

"I am the Muskrat," said the wretched creature faintly. "A philosopher, you know. I should like to point out that your bridge-building activities have completely ruined my house on the river bank, and although ultimately it doesn't matter what happens, I must say even a philosopher does not care for being soaked to the skin."

Posted at 12:37PM on 6 May 07. Permalink.

I've been reading a few books on pre Columbian America, the most recent of which went into a bit of detail about this charcoal technique, and some other interesting techniques used by the Mayans.

Generally a pretty depressing read, but then a genocide by disease is never going to be high in lols.

Posted at 1:40PM on 6 May 07. Permalink.

By my everlasting tail, you're right, it COULD be the muskrat - darn tiny gravatars - but it's meant to be the Groke:

Then - they saw the Groke. Everybody saw her. She sat motionless on the sandy path at the bottom of the steps and stared at them with round, expressionless eyes. She was not particularly big and didn't look dangerous either, but you felt that she was terribly evil and would wait for ever. And that was awful.

Being something of a science klutz, I'm very appreciative of such marvellous communicators as Colin Tudge and Tim Flannery, who make the most vital and fascinating information accessable. Flannery's regular radio spot with John Doyle on Sydney's 2BL in the 90s was a must-listen for me. While I'm familiar with the account of aboriginal firestick farming from The Future Eaters, the 'Maori soils' stuff was news to me. What you're doing here is terrific, thanks again.

Posted at 7:10AM on 7 May 07. Permalink.

Another great story. I'm enjoying these public address science transcripts.

its quite good to think of all the stuff you can use to produce charcoal, like green waste and tyres. thats killing a lot of birds with one stone (to mangle an analogy)

Posted at 10:59AM on 7 May 07. Permalink.

I too am really enjoying the public address science transcripts.
Do you know if Aotearoa biocarbon are actually looking at liscencing the flash-burner from UH to make carbon for agriculture?
I was a bit worried about by-product pollution too, but it's nice to see that although they aren't claiming it doesn't produce smoke and tar, they've got a funding grant to investigate ways to adapt the tecnology to reduce the byproducts.

Posted at 11:17AM on 7 May 07. Permalink.

Jo S wrote:

Do you know if Aotearoa biocarbon are actually looking at liscencing the flash-burner from UH to make carbon for agriculture?

I think there's a degree of commercial sensitivity about some of Aotearoa Biocarbon's plans -- but I do know that they are very impressed with UH's work in this area. I'll see if I can get them to comment.

Joe Wylie wrote:

...it COULD be the muskrat - darn tiny gravatars - but it's meant to be the Groke

They do bear a remarkable similarity (when you can't see them actual size).

I must say that it takes a certain type of person to use the Groke as a gravatar, and not to overwhelm their fellow Public Address readers with nameless, inescapable dread. But you're doing quite a good job of it so far.

Posted at 11:33AM on 7 May 07. Permalink.

Finn Family Moomintroll! one of my favourite kids' series ever! I'd completely forgotten about them, thanks for the reminder David/ Joe...

Fascinating post, I'm willing to bet that solutions to global warming lie in the soil and the sea, as bacteria & fungi are the main regulators of global nutrient & energy cycles. It's all very tantalising, hope we hear more...

Posted at 11:45AM on 7 May 07. Permalink.

Really interesting
And it will be even more interesting to see how this would balence out in energy terms ie energy needed to produce charcoal, carbon released into the atmosphere compared with carbon locked up in the soil
And even more importantly how the deep burying of charcoal would effect the fertility of the various soil types in New Zealand especially the cropping types

Posted at 12:06PM on 7 May 07. Permalink.

Great post David!

And very topical considering the International Agrichar Initiative in Australia linked by Joe.

Would you be kind enough to add the energybulletin.net Terra Preta links page to your further information section?

cheers!

[**REPLY:** Thanks, Stephen, I've done that -- DH]

Posted at 2:41PM on 7 May 07. Permalink.

Raymond A Francis wrote:

And it will be even more interesting to see how this would balence out in energy terms ie energy needed to produce charcoal, carbon released into the atmosphere compared with carbon locked up in the soil

Not only to produce the charcoal, but also energy (and $) costs for transporting the wood/charcoal and incorporating it in the soil. Transport is one of the problems in dealing with wood waste and residues from the forestry sector.

What effects would mechanical tilling of very large areas to 40cm depth have on soil stability and sediment runoff?

Posted at 1:41AM on 8 May 07. Permalink.

Please excuse me for being off topic slightly, er perhaps more than slightly.
But could anyone confirm some anecdotal info I had lately - Hemp biomass is highest in cellulose, as well as an excellent nitrogen-fixer. Grows like a weed.
And if this is correct, why aren't we growing more of it ?

Posted at 10:56AM on 8 May 07. Permalink.

Jo S wrote:

Do you know if Aotearoa biocarbon are actually looking at liscencing the flash-burner from UH to make carbon for agriculture?

Yes, licensing is one option we are investigating at Aotearoa Biocarbon.

Posted at 11:03AM on 8 May 07. Permalink.

One of the really important things, well borne out by our own experiments as well as other results presented at the IAI, is that indigenous use of biomass was site specific. Soils do vary and the soils in Brazil and Japan where the biggest effects have been seen are what are known as soils of variable charge which will ring some bells for those who know anything about andasols and their distribution in Aoteaoa/New Zealand! Indigenous people used any local material that was effective in growing plants better. Indigenous people in Brazil used pottery chards in some instances. Maori in the Waikato used pumice sand. Now there is a challenge for you thinkers out there. I'll give you a week to think about it!!
Alfred Harris

Posted at 11:20AM on 8 May 07. Permalink.

paulalambert wrote:

... could anyone confirm some anecdotal info I had lately - Hemp biomass is highest in cellulose, as well as an excellent nitrogen-fixer. Grows like a weed.
And if this is correct, why aren't we growing more of it?

While I love universal panaceas, hemp is not a nitrogen fixer...

Posted at 3:34PM on 8 May 07. Permalink.

I wondered if there had been any link established between the incidence of Terra Preta soil sites and Maori cooking practices: i.e. hangi?

Posted at 5:12PM on 8 May 07. Permalink.

__ ... could anyone confirm some anecdotal info I had lately - Hemp biomass is highest in cellulose, as well as an excellent nitrogen-fixer. Grows like a weed.
And if this is correct, why aren't we growing more of it?__

While I love universal panaceas, hemp is not a nitrogen fixer...

It has many other virtues, though. And it is legal these days.

Posted at 10:21AM on 9 May 07. Permalink.

Hi David

Thanks for setting up the RSS feed for PAS. It's now on the AgResearch podfeeder page alongside New Scientist, Science, Nature, Heredity and USDA podcasts!

This story was very interesting - I already knew people were proposing it for carbon sequestration but I did not realise it was also really good for the soil.

Keep it up, I look forward to each one.

Benjamin

Posted at 1:27PM on 9 May 07. Permalink.

Posted on behalf of Foss Leach:

Regarding charcoal in pre-European Maori garden soils: What is important here is to consider the mental process involved. There is no direct evidence that any Polynesians (including Maori) deliberately set out to improve the fertility of dryland soils by adding things such as charcoal, human waste, or rotting vegetation. I have come across modern evidence that sharks were rotted in taro ponds as fertiliser on an atoll, Kapingamarangi, but just how ancient this activity is is unknown.
Polynesians fallowed soils when they were exhausted - that is a different mental template. In addition, Maori certainly did deliberately add coarse sand to garden soils. This has a number of useful effects, as has been shown experimentally, such as improving drainage and changing the thermal character of garden soils. Which one or more of these effects effects pre-European Maori had in mind when they did this is of course unknown. This is not a case of fertiliser.

In the case of charcoal, this is frequently found in archaeological soils known to have been planted for gardens. The distribution of charcoal is variable and from several sources - burning of vegetation during preparation of gardens, wind-blown charcoal from fires further afield, and cooking events within gardens. These activities do not involve the mental process of "I am fertilising this soil by putting charcoal in it". In archaeology, as in any other branch of science,
we try to keep guess work out of what we do.

Posted at 8:12PM on 9 May 07. Permalink.

Foss Leach wrote:

There is no direct evidence that any Polynesians (including Maori) deliberately set out to improve the fertility of dryland soils by adding things such as charcoal...

Thanks for posting Prof Leach's comments, Owen. From the papers I'd read there seemed to be very good evidence that the Amazonians deliberately used charcoal -- but, unfortunately, I must have got my wires crossed when it came to evidence of deliberate use of charcoal by Maori.

My apologies for that. I have emended the transcript and audio to change the words from:

...pre-European Maori also worked charcoal into the soil to improve fertility.

to:

...pre-European Maori also worked charcoal into the soil.

Please pass on my thanks to Prof Leach for pointing out my mistake. I do go to a lot of effort to prevent any error of fact in my journalism -- but (obviously) this one got past me.

I shall attempt to be more vigilant in future!

Posted at 3:04PM on 10 May 07. Permalink.

Hemp biomass is highest in cellulose, as well as an excellent nitrogen-fixer. Grows like a weed.
And if this is correct, why aren't we growing more of it ?

Don't know if it is the highest but there are a lot of plants that are very high in cellulose. Often it's not the cellulose that is the issue it's the other things like lignans that create problems with using the cellulose. Whatever processing system you want to use gets clogged up or the product devalued by the contaminants.

As for hemp in particular, my guess is the carbon economics would be aweful given the amount of papaerwork required to get through ther bureaucracy :).

cheers
Bart

Posted at 6:32AM on 29 May 07. Permalink.

Yes, a very, very good point. Kumara was one of the foods of chiefs. Karaka may well have been another. As such, most records show that the kumara brought to Aotearoa by Maori were tended as individual plants.
In the Amazonia, a lot of the beneficial charcoal effect seems to have come from the addition of animal fertiliser. No big mammal poopies in Aotearoa!! But what there was was cooking juice infused charcoal (new charcoal and probably under pressure!) I am sure that someone would have noticed very early on (if the knowledge wasn't brought from umu cooking in Hawaiki) that these charcoals made plants grow really well.

Posted at 6:41AM on 29 May 07. Permalink.

Foss Leach wrote:

There is no direct evidence that any Polynesians (including Maori) deliberately set out to improve the fertility of dryland soils by adding things such as charcoal...

Your comments are not supported by the archaeological literature. The critical paper, very kindly pointed out to me by Owen Wilkes, and completely missed in the recent DOC "Maori gardening" publication is : McNabb. J. W. Sweet potatoes and Maori terraces in the Wellington area. J. Polynesian Society. 1969 78: 83-111

This has a superb review of kumara production in Aotearoa, including clear evidence that 100's of acres in Waimea and the Waikato was systematically altered with charcoal, up to 40cm deep in the soil.

It is often the assumptions we make about "primitive" cultures that blinker us so that we miss the obvious, both archaeologically and rationally.

Posted at 6:45AM on 29 May 07. Permalink.

Revisions of history, in the absence of critical thinking, are a dangerous things. I stand by my original comments and look forward to Foss Leach's reply after reading the reference cited in the earlier posting.
Alfred Harris

Posted at 6:27PM on 14 Jun 07. Permalink.

On behalf of Foss Leach:
I am surprised at the comments made by your correspondent because there was nothing primitive about these ancient gardeners at all; on the contrary. I have great admiration for the way that pre-European Maori so quickly adapted their horticultural practices to the harsh New Zealand conditions when arriving here from the Pacific with tropical root crops. There is abundant archaeological evidence of the diligent and enterprising research which these people
carried out in order to find ways of successfully growing and storing these root crops in the face of great difficulties with this unfamiliar and generally unsuitable climate. Their experimental research on subterranean storage pits is an excellent example of this. So too, the way that they deliberately modified poorly drained soils by the addition of coarse sand and fine gravel. This practice had a number of beneficial effects on garden soil for tropical root crops, not all of which may have been anticipated.

Yes of course all archaeologists are familiar with the literature your correspondent cites; but I must point out that there has been a great deal of authoritative research on ancient gardens since these two papers were published so long ago (Rigg and Bruce 1923, and McNab 1969).
For example, Mike Burtenshaw of the Open Polytechnic of New Zealand is near the end of a ten-year research project examining changes in soil fertility in experimental garden plots growing traditional kumara cultigens. As far as the use of charcoal as a fertiliser is concerned, I can only suggest that my earlier comments on this matter should more carefully be read again.
There is no archaeological evidence, or for that matter any other form of evidence, that pre-European Maori deliberately added charcoal to garden soils in an effort to improve fertility.
Charcoal occurs in garden soils in dense localised patches where people were burning rubbish (this is not fertilising activity) just as we still do today. Charcoal also occurs as finely divided particles more evenly distributed in soils both inside and outside gardens due to forest fires nearby (again this is not a fertilising activity).

On the subject of `other forms of evidence', early Europeans in New Zealand were in an excellent position to observe and record at first hand the gardening activities and knowledge of Maori about such issues as the agencies of fertility. One of most astute of these observers was William Colenso, who had this to say: "One striking peculiarity, however, should not be omitted - in which, too, I think, they differed from all agricultural races - their national non-usage of all and every kind of manure ... They also never watered their plants, not even in times of great drought, with their plantations close to a river, when by doing so they might have saved their crops" (Colenso 1880: 11). Surely this should dispell any doubt on this subject?

Finally, on the question of "would adding charcoal to soil make it more fertile?" I asked a senior soil scientist at the Hill Laboratories in Hamilton this question and got the clear answer: "Charcoal No, but ash perhaps". And just to show that even experts don't always know everything, I refer the interested reader to some recent scientific research by Lehmann et al. (2003) which suggests that the addition of charcoal to soil may indeed do exactly what it is purported not to be able to do. The reasons for this are complex, not well understood, and the subject of ongoing research.

Colenso, W. 1880. On the vegetable foods of the ancient New Zealanders before Cook's visit. Transactions and Proceedings of the New Zealand Institute 13: 3-89.

Lehmann, J., Silva, J.P. de, Steiner, C., Nehls, T, Zech, W. and Glaser, B. 2003. Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the central Amazon basin: fertilizer, manure and charcoal amendments. Plant and Soil 249: 343-357.

McNab, J.W. 1969. Sweet potatoes and Maori terraces in the Wellington area. Journal of the Polynesian Society 78(1): 83- 111.

Rigg, T. and Bruce, J.A. 1923. The Maori gravel soil of Waimea west, Nelson, New Zealand. Journal of the Polynesian Society 32: 85-93.