Receptiveness of some tropical soils from banana fields in Martinique to the arbuscular fungus Glomus intraradices

Tropical crops of great economic importance such as banana are known to benefit from mycorrhizal association. Development and survival of introduced mycorrhizal propagules depend not only on the crops but mainly on the edaphic conditions and soil types where the symbiosis is established. Seven soils from banana fields of Martinique were sampled and tested to determine their receptiveness to mycorrhizal inoculation. Biological tests involved cultivation of 10 leek plantlets in pots containing soil inoculated with a range of mycorrhizal propagule densities (3, 10, 30, 100, 300 propagules/100 g soil). Mycorrhizal colonisation was recorded after 2 weeks of growth and tentatively correlated with inoculum density. For each soil regression equations enable determination of the number of propagules needed to induce mycorrhizal colonisation of 50% of the leek plantlets. This measurement unit parameter value was called ‘the mycorrhizal soil receptiveness 50 (MSR 50) unit’. Values recorded varied from 22.7 (for Fafane, Enterrement, Parc à veaux soils) to 96.7 propagules/100 g (for the Morne-vidou soil). Soil receptiveness tended to decrease when the number of propagules increased. Multiple regression tests between MSR 50 unit values and soil parameters (pH, P, Cu, Zn, CEC, N) permitted development of mathematical equations enabling prediction of mycorrhizal soil receptiveness.