Full Length Research Paper

Response of Gliricidia sepium tree to phosphorus application and inoculations with Glomus aggregatum and rhizobial strains in a sub-Saharian sandy soil

Adama Diouf^1,2*,Tahir Abdoulaye DIOP^1,3, Ibrahima Ndoye³ and Mamadou Gueye^2,3

¹Laboratoire de Biotechnologie des Champignons, Département de Biologie Végétale, Faculté des Sciences et Techniques UCAD B.P 5005, Dakar, Sénégal

²MIRCEN/ISRA, Centre de recherche de Bel Air, B.P. 1386, Dakar, Sénégal.

³Laboratoire Commun de Microbiologie IRD/ISRA/UCAD, Centre de recherche de Bel Air, B.P. 1386, Dakar, Sénégal.

*Corresponding author. E-mail: adiouf97@yahoo.com.

Accepted 28 January, 2008

A pot experiment was carried out in a green house at Bel Air station to determine effect of phosphorus on the growth of Gliricidia sepium in presence of rhizobial strains and an arbuscular mycorrhiza fungus. A factorial 3 factors block was designed with arbuscular mycorrhizal fungus Glomus aggregatum, phophorus fertilization as triple super phosphate and rhizobial inoculation strains ISRA 604 and ISRA 605 applied on G. sepium seedlings. A non nitrogen fixing tree (NFT), Cassia siamea was used as reference tree for estimating the nitrogen fixation using the ¹⁵N isotope dilution technique. Mycorrhizal infection, nodulation, plant growth, P and N contents, ¹⁵N atom % excess (¹⁵Nae) and N fixed were determined. The results showed that the rhizobium strain ISRA 604 induced nodulation more than ISRA 605 in G. sepium with an increase of 38.28% for nodules number. Frequency (%F) and intensity (%M) of mycorrhization were highest at 0, 20 and 40 mg P kg^-1 soil applied however rhizobial inoculation has influenced frequency of mycorrhization. In the rhizobium- AM fungus interaction, plant shoot total N content increased when trees were inoculated with G. aggregatum whatever the rhizobial strain inoculated. Roots N fixed (Ndfa) increased when plant was inoculated with ISRA 604 and amended with 20 mg P kg^-1 soil. The inoculated plants exhibited the highest total nitrogen in whole plant as well as in shoots and roots than in non-inoculated and reference plants. G. sepium growth benefited from selected rhizobia and AM fungus inoculations and P application in a sandy soil.

Key words: Arbuscular mycorrhizal fungus, Gliricidia sepium, nitrogen fixation, phosphorus, rhizobium.