U.S. Department of Agriculture’s science magazine (November/December 2011 issue) have a interesting article about scientific trials using various types of Biochar.

The html Article is available here >>>>

I have to say that from my many years of using many different types of Biochars in my own sandy loam soils that I now never apply Biochar directly to my soils, apart from Biochar made in continuous flow pyrolysis using poultry litter as the feedstock as the process retains a lot of the manure nutrients and I always soak it in biological nutrient liquids before applying.
The idea of tipping 50 tonnes of wood Biochar per hectare in one hit is not the way to do it from my point of view. Biochar needs to be blended with high biological and nutrient blends, good quality humus compost is my preferred blend. It needs to be applied slowly over many seasons. Adding something as complex as Biochar in such high rates would seriously effect soil biota which may take years to balance and start to produce positive results.

My other issue is trialling 50 tonnes per hectare. Going on a low price of $500 per tonne of Biochar that’s $25,000 per hectare. I think some of these soil scientists need to get a better idea of what agribusinesses could really afford and focus their budgets on realistic trials.

From what I have read on the Amazon Terra preta soils, it is a blend of both char and other organic nutrient elements, we should be focusing our research on blending Biochar in useful ways which are economically viable.