I had a brief correspondence with Dr N. Sai Bhaskar Reddy from India on his trials on alkaline soils which I am copying here.
I think that sizing is not a particularly critical factor, except for convenience. This is a bit of a surprise as I would have expected that fine grained powder would maximize the overall homogeneity of the soil. What appears to be happening is that the root system responds to the presence of the charcoal even at some tangible remove. This clearly suggests that while fines are likely preferred in special cases, they are not at all necessary.
My reading on the terra preta soils showed that the majority of carbon was very fine grained as would be expected from a corn stover. This also accounts for the high percentage of carbon in the soil. There never was a reason to quit adding carbon.
On the other hand, using wood charcoal is obviously totally feasible with a preliminary screening to create an easy to spread product.
One of the concerns with fresh charcoal is that there is still sometimes a residue of acids that seem to slow integration into the soils. It seems that alkaline soils would naturally offset this particular temporary effect.
The important observation is that from fields that were essentially barren, he is abruptly getting good results. This gives us a simple protocol to reverse alkaline damage to soils. I do not know if the source of the alkalinity is actually removed over time but we now know that it may no longer matter.
The take home lesson is to take your poorest field and get it treated with a dressing of charcoal, however obtained. You will quickly gain confidence and the results will be very pronounced. So far, absolutely no special nonconforming soils have been discovered, but the real test will come when someone tries this out on a salt rich soil. I am not optimistic regarding those conditions but it may still be possible to make something work even there were common sense says no.
One thing that I should comment on, that is not too obvious is that the effect of powdering causes the surface area in contact with the soil to climb exponentially. A simple grind has a huge increase in the availability of active contact. Taking the grind down to the nanometer scale generates a massive increase in effectiveness. The problem is usually that it is not cost effective to reach this scale and I suspect that the biology quickly surrounds the particle, perhaps then inhibiting the effects.
The corn char derived terra preta likely demonstrate this effect when compared to far coarser wood derived charcoals. A soil containing 15% finely powdered as in the terra preta should do far better than our wood based soils of the same carbon percentage.
Dear Robert Klein,
In the alkaline soils, I got very good results for two seasons. The soil condition has improved and expected to get better results in the next 4 years. The charcoal located within a depth of 8 inches, breaks during ploughing and other activities done in the farm. Regarding using powder charcoal / lumps of charcoal, I prefer lumps of charcoal for the following reasons. A part from the reason mentioned by you.
- The recent report clearly shows that the roots prosper about a piece of charcoal.
- Lump can provide better environment
- Lump is heavy so less chance of moving due to wind or water away from the field
- Adds texture to the soil
- Soil microbes and soil fungus would find convenient place in a lump of charcoal and can live as a community.
There could be many more reasons.
Dr. N. Sai Bhaskar Reddy
On 6/24/08, Robert Klein <firstname.lastname@example.org> wrote:
Hello Dr Reddy
I am curious how your experiments have been working out on alkaline soils.
As an aside, you are using wood charcoal obviously. Can you get it to break up in the soil when you hoe the ground?
I am thoroughly convinced that the amazonians used corn stover primarily for their biochar and that would have yielded a finely powdered carbon. Check with me if you want to know how this was done.
The recent report clearly shows that the roots prosper about a piece of charcoal. I actually knew that from my own boyhood. Whoever thought that that would be important?