Field experiments were conducted to determine the effect of irrigation intervals combined with different types of fertilizers on the incidence of damping-off and charcoal-rot, percentage of fungi in rhizosphere and rhizoplane, yield and oil content of sunflower. Application of irrigation intervals combined with different types of fertilizers significantly affected incidence of diseases and density of fungi in the soil. The irrigation at 20 days intervals combined with gypsum as a fertilizer, significantly decreased incedence of damping-off and charcoal–rot diseases 4.66%, and 31.66%, respectively, followed by the same irrigation treatment combined with phosphoren 5.66% and 38.31%, respectively in the two successive growing seasons 2007 and 2008.
The irrigation interval treatments combined with farmyard manure stimulated the growth of some fungi in the rhizosphere and rhizoplane of sunflower plants compared to other fertilizers. Meantime, gypsum as fertilizer application under the irrigation intervales conducted decreased the percentage of micro-organisms in rhizosphere and rhizoplane, 42.8% and 40.8%, respectively, compared with other fertilizers. Penicillium sp < /em>. and Fusarium sp < /em>. were the dominant fungi in all tested rhizosphere and rihzoplane samples of sunflower. Also, irrigation at 20 days intervales combined with each fertilizers improved sunflower growth, yield and increased oil as well.