الفهرس 
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Abstract
Due to alkal inity of Egyptian soils, the unavailability of phosphorus to plants is considered to be one of the important problems of fertilization in Egypt; thus phosphorus fertilizers can represent a significant component of variable costs in the cropping system Furthermore, phosphorus applied to the soil as water-soluble fertilizers is quicklv converted to forms not available to plants as indicated by its lower extract ability form the soil. Under these conditions, it is better to utilize less soluble and less expensive phosphorus sources, in association with microorganisms (i.e. phosphate dissolving bacteria, PDB) that can either solublize phosphate or enhance its absorption form slowly soluble forms in the soil. en the other hand, soil available water plays an importantrole on increasing the activity of POB and in plant growth and yield. Either over irrigation or shortage of water causes serious crop damage. In addition, sunflowe. seeds are rich source of oil. Great emphasis has been given to sunflower for oil industry due to its adaptability to various environmental conditions due to its short growing seasons and much need to fill the gap between the vegetative oil production and consumption.