Importance of indigenous arbuscular mycorrhiza for growth and phosphorus uptake in tropical forage grasses growing on an acid, infertile soil from the Brazilian savannas

A pot experiment was conducted to examine the significance of indigenous arbuscular mycorrhizal fungi (AMF) for growth and phosphorus uptake in some important introduced forage grasses at different soil pH levels in a Brazilian Oxisol. Plants of Brachiaria brizantha (BB), B. decumbens (BD), B. humidicola (HU) and Panicum maximum (PM) were grown in a glasshouse for 70 days with or without inoculation with indigenous AMF at 3 levels of initial soil pH (4.3, 5.1 and 6.4). After the growth period, dry weight, concentration of phosphorus (P) and P uptake were determined in both shoots and roots. Inoculation with AMF increased both shoot and root dry weights in BD, BB and PM, but not in HU. Shoot and root P concentrations and total P uptake per pot in all species were improved by mycorrhizal inoculation. Plant growth and P uptake were directly related to soil pH in all grass species. All grass species showed the highest mycorrhizal dependency for dry matter production and P uptake at the lowest soil pH level.