Stimulation de la croissance du maïs et de la laitue romaine par des microorganismes dissolvant le phosphore inorganique

Abstract

Phosphorus solubilizing microorganisms constituted 26 to 46% of the microbial population of the four Quebec soils studied. Among the microorganisms isolated 10 bacteria and 3 fungi were selected for their ability to form a large clarification zone on solid media containing different insoluble P salts. In a glasshouse assay, the inoculation of maize seeds with the 13 organisms selected did not significantly influence maize growth or P content, after 3 weeks of growth. In field trials, the Enterobacter sp. isolates 22a and 22c and the Pseudomonas sp. isolate 24 significantly increased (7–9%) plant height after 60 days of growth. After 108 days of growth, only isolate 22c caused a significant increase (23%) of shoots fresh mass. Field trials with Paris Island Cos lettuce seeds inoculated with the bacterial isolates 22a and 24 resulted in 14 and 18% increase in shoots fresh mass yields, respectively. Isolate 68 of Rhizopus sp. also increased lettuce yield by 11% over the control. The growth improvement observed in maize and lettuce probably did not result only from P solubilization activity but also, in part, from the ability of the four organisms inoculated to produce siderophores and auxins.Key words: microbial solubilization, phosphorus, corn, lettuce.