Abstract

We tested termite mound materials belonging to different
feeding groups: Cubitermes (soil-feeder), Trinervitermes (grassfeeder)
and Macrotermes (litter-feeder), as natural microbial inoculum to
promote plant growth and increase nutrient supplies from soil organic
matter and inorganic amendments (rock phosphate), through their effects
on soil microorganisms (functional diversity of soil microflora,
arbuscular mycorrhizal fungi, rhizobia, fluorescent pseudomonads,
actinomycetes and saprophytic fungi). Experiments were made in a pot
experiment with Acacia seyal, a leguminous tree abundant in West Africa,
with a sandy soil amended or not with rock phosphate. Results indicated
a stimulation of plant growth with Cubitermes and Trinervitermes mound
powder (plant height and shoot biomass), similar to what was obtained
with rock phosphate alone. Leaf content in N was also increased in the
termite treatments (except in Macrotermes soil), whereas mycorrhizal
colonization was inhibited as compared to the control. The development
of saprophytic fungi was significantly higher in the soils amended with
rock phosphate and this effect was hypothesized to be related to the
production of large quantities of oxalic acid by fungal populations. The
fluorescent pseudomonad populations notably increased in the soils
dually amended with mound powders and rock phosphate, and this could be
due to the fact that some species of this bacterial group are able to
dissolve rock phosphate. The organic and inorganic amendments decreased
the soil catabolic evenness in all the mound powder treatments. Among
the mound materials tested, Cubitermes mound powder had the most
promising effect, especially on SIR response to oxalate. It is concluded
that soils amended both with rock phosphate and Cubitermes mound soil
could promote the development of microbial communities, which could help
to metabolize this compound and consequently enhance plant growth.