Submitted to: Extension Publications
Publication Type: Other
Publication Acceptance Date: May 11, 2010
Publication Date: N/A
Technical Abstract: Humic products are extracts of lignite or leonardite, which are immature coals. Humic products are sold commercially; their advertisements claim they will improve plant growth when applied to plants or soil. They are bought by small proportions of row crop farmers and growers of flowers, vegetables, and turfgrass. Rigorous proof for their benefit to plant growth is scarce in the scientific literature. This presentation summarizes the existing knowledge on the field effectiveness of humic products for improving plant growth. It draws on scientific literature, an extensive 2009 evaluation of one humic product in corn (Zea mays L.) production fields of central Iowa, and reviews of their own field evaluations that were presented by humic product manufacturers at a recent conference. Key challenges facing the humic industry are also discussed, including the absence of a widely accepted procedure for verifying humic and fulvic contents of commercial products, the absence of quality control measures, and the lack of mechanistic understanding regarding how humic products improve plant growth.