types, but they were very specific chars for specific soil types. Essentially biochar properties vary by original substrate type and processing (as you've noted), which then changes the way these chars will interact with the soil chemistry. Soil chemistry obviously varies so the chars will react differently to different soil types. If it is the study I'm thinking of it would have been Paul Blackwell's work, worth looking it up. He did find that some biochars worked on some soil types, but they were very specific chars for specific soil types. Essentially biochar properties vary by original substrate type and processing (as you've noted), which then changes the way these chars will interact with the soil chemistry. Soil chemistry obviously varies so the chars will react differently to different soil types. Of course Aussie soils are a different beast to other soil types, so it appears that biochars may be a better fit in other areas of the world, but the same caveats apply. Sohi, S., E. Lopez-Capel, et al. (2009). Biochar, climate change and soil: A review to guide future research. CSIRO Land and Water Science Report 05/09. CSIRO Land and Water Science Report 05/09. 05/09 Tim, I think we are mostly on the same page. I concentrate on pushing the productivity line rather than the CFI line with soil carbon, the tipping point will come when the mechanism is simple enough and the price is high enough to give incentive to grow carbon levels for BOTH productivity gains