Rock phosphate and vesicular-arbuscular mycorrhiza effects on growth and mineral nutrition of Zizyphus mauritiana Lam. in an alkaline soil

7The influence of vesicular-arbuscular mycorrhizae (VAM) and rock phosphate (RP) was studied on jujube (Zizyphus mauritiana Lam.), a multipurpose fruit tree in Sahelian agroforestry systems. Jujubes were inoculated or not by Glomus manihotis Howeler, Sieverding & Schenck in an alkaline sandy soil to which were added five levels of RP (12 % of P) : 0.00, 0.31, 0.62, 1.25 et 2.50 g P/kg of soil, equivalent to 0, 775, 1 550, 3 125 et 6 250 kg P ha(-1). The jujubes seedlings grew poorly without mycorrhizal colonization and without RP applications (figures 1a, b). Non-VAM jujubes were able to utilize P from PN efficiently (figure 1g). However, VAM jujubes with RP applications achieved better results in terms of height, biomass, concentrations of P and N in stem plus leaves. Mycorrhizal dependency varied from 78 % to 18 % when RP applications increased (figure id). Mycorrhizal colonization was comparable at all levels of RP applications and reached at lease 80 % (figure 1e). There were not additive effects of inoculation and fertilization on total biomass of jujubes at any RP applications. However, mycorrhizal jujubes took up more P and N at 0.62 g P kg(-1) of soil and above. These results suggest that VAM are able to absorb P from soil and rock phosphate for a better mineral nutrition of jujubes. (C) Inra/Elsevier, Paris.