Effect of Arbuscular Mycorrhiza fungi application on distribution of phosphorus forms in rhizosphere soils of sunflower (Helianthus annuus L.)

Appropriate management of soil phosphorus (P) fertility in highly calcareous soils of Iran as around the world should rely upon sound knowledge about the phosphorus reserve and its bioavailability. Despite numerous reports on the positive effects of vesicular arbuscular mycorrhizae (VAM) fungi on phosphorus uptake which is associated to Ectomycorrhiza as a branch of two major branches of group of fungis from mycorrhizal association, surprisingly little data exist on impact of VAM fungi on distribution of soil phosphorus forms in soils. A greenhouse-based study was conducted to investigate the potential effects of Arbuscular Mycorrhizal (AM) fungi application on phosphorus inorganic forms of soil rhizosphere in sunflower plants (Helianthus annuus L.). Results indicated that there is a significant increase in Fe-P fractions (P < 0.001) in the rhizospher of the treated sunflowers with AM inoculums compared with untreated sunflowers. It could be potentially attributed to increases in secretion of specific–iron chelates such as hydroxamate siderophore from sunflower roots in +AM sunflowers treatments.