Submitted to: Bioresource Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/13/2009
Publication Date: 12/31/2009
Citation: Douds, D.D., Nagahashi, G., Hepperly, P.R. 2009. Production of inoculum of indigenous AM fungi and options for diluents of compost for on-farm production of AM fungi. Bioresource Technology. 101:2326-2330. Interpretive Summary: Arbuscular mycorrhizal (AM) fungi are beneficial soil fungi that form a symbiosis with most crop plants. Since the primary benefit to the plant is increased uptake of nutrients, optimal usage of these fungi is essential if the goal is to reduce or eliminate chemical fertilizer inputs. Earlier, we developed a method for the on-farm production of inocula of these fungi which required transplanting grass seedlings, already colonized by specific species of AM fungi, into bags filled with compost and vermiculite. Adoption of this method by farmers is inhibited because of 1) fears of asbestos contamination of vermiculite and 2) commercial unavailability of colonized grass seedlings. We conducted experiments to find substitutes for vermiculite and develop techniques to grow AM fungi indigenous to the farm so as to make precolonized grass seedlings unnecessary. Perlite and peat based horticultural potting media, both commonly used in agriculture, were satisfactory substitutes for vermiculite. Two methods of propagating AM fungi indigenous to the farm also were successful: 1) mixing field soil right into the compost and vermiculite media and 2) pre-growing grass seedlings, prior to transplant into the bags of compost and vermiculite, in a potting mix containing a small amount of field soil. The flexibility these modifications give will make it easier for farmers to produce inoculum of AM fungi on-the-farm and help them take advantage of the benefits of this symbiosis.
Technical Abstract: Technical Abstract On-farm production of arbuscular mycorrhizal [AM] fungus inoculum can be employed to make the benefits of the symbiosis more available to vegetable farmers. Experiments were conducted to modify an existing method for the production of inoculum in temperate climates to make it more readily adopted by farmers. Perlite, vermiculite, and peat based potting media were tested as diluents of yard clippings compost for the media in which the inoculum was produced using bahiagrass (Paspalum notatum Flugge) as host plant. All produced satisfactory concentrations of AM fungus propagules, though vermiculite proved to be better than potting media (89 vs. 25 propagules cm-3, respectively). Two methods were tested for the growth of AM fungi indigenous to the farm: 1) adding field soil into the vermiculite and compost mixture and 2) pre-colonizing the bahiagrass seedlings in media inoculated with field soil prior to transplant into that mixture. Adding 100 cm3 of field soil to the compost and vermiculite produced 465 compared to 137 propagules cm-3 for the pre-colonization method. The greater flexibility these modifications give will make it easier for farmers to produce inoculum of AM fungi on-the-farm.