Submitted to: Compost Science and Utilization
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2014
Publication Date: 10/15/2014
Publication URL: http://handle.nal.usda.gov/10113/59997
Citation: Douds, D.D., Lee, J., Uknalis, J., Boateng, A.A., Ziegler-Ulsh, C. 2014. Pelletized biochar as a carrier for AM fungi in the on-farm system of inoculum production in compost and vermiculite mixtures. Compost Science and Utilization. 22(4):253-262. Interpretive Summary: Arbuscular mycorrhizal [AM] fungi are naturally occurring soil fungi that form a beneficial symbiosis with roots of the majority of crop plants. Crops that are colonized by AM fungi are better able to take up nutrients from the soil and resist diseases and drought than plants not colonized. Optimal utilization of this symbiosis should be an essential aspect of sustainable agricultural systems. We have developed a method for farmers to grow their own inoculum of AM fungi on-the-farm for use as an amendment to potting media for the production of plants in the greenhouse. This is fine for vegetables, however, this inoculum is not amenable to mechanical application to the field for the production of large-scale crops such as corn and soybeans. We tested the idea that if the AM fungi would proliferate on and within pellets of charcoal mixed into the media in which AM fungi are produced in the on-farm inoculum system, those pellets could then be used as units of inoculum that could be delivered to the field by seeding or fertilizer spreading machinery. Results were very promising: microscopic analysis found AM fungus structures on the charcoal pellets and those pellets were found to produce colonization of new plants in the greenhouse. This work represents an important step in expanding the use of AM fungus inoculum and enhancing the sustainability of US agriculture.
Technical Abstract: On farm production of arbuscular mycorrhizal [AM] fungi is suitable for vegetable and horticultural crop production because the inocula may be efficiently mixed into horticultural potting media for plant production in the greenhouse. These inocula are not amenable for use in row crop production because they are not in a form suitable for mechanical application. Experiments were conducted in which light expanded clay aggregates [LECA] and pelletized biochar were used in the media for the on-farm production of AM fungus inoculum in utilizing compost and Paspalum notatum Flugge as the nurse host plant. Subsequent colonization assays using P. notatum failed to detect any infectivity of LECA granules, indicating that the AM fungi did not infest the granules. However, as little as 0.1 g fresh wt of biochar was sufficient to produce colonization of test plants. Biochar pellets recovered from the on-farm system used to propagate Glomus intraradices exhibited 24 propagules g-*1 fresh wt. These results indicate the promise of pelletized biochar as a carrier for AM fungi in inoculum production systems.