ARS | Publication request: Germination tests for assessing biochar quality

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 13, 2011
Publication Date: N/A

Interpretive Summary: Biochar are co-products of renewable fuels created during pyrolysis of biomass and a new soil amendment offering increase productivity to marginal soils. However, their acceptance as soil amendments is dependent on their agronomic quality that varies depending on source material and conditions used during pyrolysis. Methods need to be develop that can rapidly determine the agronomic value of a biochar. Seed germination and growth characteristics were used to assess the agronomic quality of six different biochar samples. The seed germination tests proved to be a reliable procedure to differentiate between effects of biochar on corn seedling growth. Research results described in this report provides needed information for growers, soil scientist, engineers, and regulatory officials determining.

Technical Abstract: Understanding the impact of biochar quality on soil productivity is crucial to the agronomic acceptance of biochar amendments. Our objective in this study was to develop a quick and reliable screening procedures to characterize the quality of biochar amendments. Biochars were evaluated by both seed germination and seedling growth. Six biochars created from varied feedstocks, thermochemical processes, and temperatures were used in this assessment. The tests included corn (Zea Maize) seed germination rate and growth of both shoot and radicle in biochar extracts and the capacity for biochar extracts to protect seedlings from allelochemicals present in corn residues. Biochars had no effect on percent germination rates; however, high temperature biochars inhibited shoot growth by an average of 16%. Germination of corn seeds in extracts of corn residue showed 94% suppression of radicle growth compared to those exposed to DI, however, biochar extracts increased radicle length 6 to 12 times relative to the corn residue extract. Biochar produced from hardwood by slow pyrolysis exhibited the greatest sorption capacity. Overall, germination tests appear to be a reliable procedure to differentiate between effects of different types of biochar on corn seedling growth.