Abstracts |
Arbuscular mycorrhizal [AM] fungi are potentially important tools in sustainable
agriculture due to their roles in crop nutrient uptake, disease resistance, and water relations
and in stabilizing soil aggregates. Inocula of these fungi can be effectively produced on-farm in
mixtures of compost and vermiculite with a suitable plant host, such as bahiagrass (Paspalum
notatum Flugge). Success of this method, however, depends upon utilizing the optimal compost and
vermiculite mixture ratio. Experiments were conducted over two years utilizing a complete
factorial design with three composts, four mixture ratios, and three AM fungi with the objective
of producing regression equations to predict optimal mixture ratios using routine measures of
compost nutrient analyses as independent variables. Growth of colonized P. Notatum in yard
clippings and dairy manure + leaf composts; which were high in N, low in P, with moderate K
levels; produced more spores of AM fungi at mixture ratios of 1:2 to 1:4 [v/v compost:
vermiculite] relative to higher dilutions. Dilution ratios of 1:19 and 1:49 were best for
controlled microbial compost, which was high in P, low in N, and moderately high in K. Simple
equations were developed which predict the optimal fraction of compost in the mixture for each of
the three AM fungi studied (Glomus intraradices, Glomus mosseae, and Gigaspora rosea). Percent N,
P, and K and N:P ratio were the significant independent variables. These equations allow a farmer
to choose a mixture ratio for the on-farm propagation of AM fungi knowing only the nutrient
analysis of the compost to be used. |