Here's some more information on char studies in the southeastern US. These are related to the collaboration between the University of Georgia and Eprida.
Pickens County Charcoal Research Project
http://www.pickensmg.com/CharResearc...l-TextCopy.pdf
A gardening club got a hold of some bio-char and did their own field tests on tomatoes and blueberries. The report should be interesting for home gardeners who want to try this themselves. It's pretty well documented and includes pictures and diagrams of their setup.
...and from a conference this past November, there's some results coming in from university field trials. Char from peanut shells seems to perform better than char from forestry wastes.
Characterization of Pyrolysis Char for Use as an Agricultural Soil Amendment.
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Abstract: Sandy soils in the coastal plain of the southeastern United States typically have very low nutrient content and cation exchange capacity (CEC). Char produced from peanut hull (PN), pine chip (PC), pine bark (PB), sawdust (SD), and hardwood chips (HW) pyrolyzed at approximately 380, 400, and 420° C were analyzed for properties that could increase the agricultural productivity of these soils. The available nutrient content of char varied with feedstock and pyrolyzing temperature. PN char pyrolyzed at 426° C (PN 426) contained the highest amounts of Mehlich I P, K, and Ca (769, 8,142, and 1,562 mg kg-1 respectively). PN pyrolyzed at 371° C (PN 371) contained the highest total N (2.03 %), but only a very small fraction was plant available based on a 24-day N mineralization study. Cation exchange capacity (CEC) of the char varied with feedstock and pyrolysis temperature. CEC ranged from 44.0 cmol kg -1 char for PN 402 to 14.1 cmol kg -1 char for the HW pyrolyzed at 426° C. CEC was significantly lower for feedstocks pyrolyzed at 420° C. Peanut hull char had a significantly higher CEC than the other feedstocks.
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Effect of Pyrolysis Char on Corn Growth and Loamy Sand Soil Characteristics.
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Pyrolysis of biomass for hydrogen fuel produces a char byproduct that may be beneficial to plant growth, improve soil conditions, and contribute to stable soil carbon. We measured corn (Zea mays) growth response and CO2 efflux in microplots (1.8 x 2.2 m) amended with peanut hull and pine chip pellet char produced at 400o C. For each char type, the treatments were: 11.2 Mg char ha-1, 11.2 Mg char ha-1 plus fertilizer, 22.4 Mg char ha-1, 22.4 Mg char ha-1 plus fertilizer, a control, and a fertilizer check (4 replicates). Soil samples were taken before plots were amended, week 4, 16 after planting, and at harvest. Soils were analyzed for pH, nutrients and C. Soil moisture and CO2 efflux from the soil surface were measured periodically during the growing season. Analyses of the char indicated that the peanut hull char at the 11.2 Mg ha-1 rate added 213 kg total N ha-1, 1.3 kg P ha-1, and 56 kg K ha-1. Nutrient additions with the pine chip char were low. Small increases in CO2 evolution in the field were observed following char incorporation. Similar short-term increases in CO2 were seen in related laboratory incubations. There was not a significant total biomass or yield response due to the pine chip pellet char. There was a significant response of stover to peanut hull pellet char alone, but total biomass and yield were not significantly higher with the char plus fertilizer treatment compared to fertilizer alone.
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