الفهرس 
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Abstract
Impact of Bio-fertilizers and Organic Phosphorus on Biological Nitrogen Fixation by Cereal Crops Using Nuclear Techniques
(Heba Gaber Hussein Attiat-Allah)
(Microbiology Department. Faculty of Science, Ain-Shams University)
Abstract
Phosphorus addition stimulates the process of biological nitrogen fixation. Maize (Zea mays L.) and pearl millet (Panicum miliaceum L.) crops may efficiently fix atmospheric N if an adequate amount of P is present in the soil. Because of the deficiency of phosphorus supply and availability remains a severe limitation on nitrogen fixation .So fungal species can be isolated and study it’s ability on organic matter (OM) degradation and phosphorus availability from organic sources to improve biological nitrogen fixation (BNF) process and the contribution of fungi and OM on growth parameters of maize and pearl millet crops . For these purposes twelve fungal strains were isolated from different parts in Egypt. from these isolates, only four fungal strains were chosen depending on their capacity to convert sparingly soluble P (tri-calcium–P ) to soluble one , clearing a halo zone on petri dish (A.niger, A.flavus, A. Ficuum and F.oxysporum) produced halo zone around the colonies. A.niger was the most efficient phosphate solubilizer on Pikovskaya’s agar plates (PVK) where solubilization index (PSI) as indicator for soluble P , 2.4 followed by A. flavus with PSI = 2.3. Because of A.niger and A.flavus showed maximum phosphate solubilization index (PSI) they were selected for further studies as qualitative and quantitative activities. The estimated soluble -P was recorded for A.niger (73.8 μg/ml), A.flavus (72.6 μg/ml) and study the effect of environmental and nutritional factors on phosphate solubilization , the more optimum conditions of P-solubility were : incubation periods 7 days and temperature 30 °C for maximum phosphate solubilization , acid and alkaline phosphatase activities . pH 7.0 for maximum phosphate solubilization, pH 6.0 for maximum acid phosphatase activity while pH 8.0 for maximum alkaline phosphatase activity for both A. niger and A.flavus , glucose as best carbon source , ammonium sulfate as best nitrogen source , tri-calcium phosphate (TCP) as phosphorus source and 2.5 g / L as best TCP concentration . Then an incubation experiment was carried out involved incubation of A.niger , A.flavus and A.niger+A.flavus with the poultry manure (PM) for different incubation periods (0,10,20,30,40,50,60 and 70 days ) . At the end , a greenhouse experiments were carried out in the green house of the Agricultural Department of Soil and Water Research , Nuclear Research Center, Atomic Energy Authority to study the effect of PM and phosphate solubilizing fungi (PSF) alone or in combination with nitrogen fixing Azotobacter chrococcum on the growth of two cereal plants (maize and pearl millet) . The results indicated that all growth parameters were increased under inoculation .Generally , PSF with PM alone or in combination with A. chrococcum plays a positive significant effect on growth parameter of the two tested plants and enhanced plant growth , shoot and root dry biomass and nutrients concentrations uptake (N , P and K) compared to control treatment .
Keywords: A.niger , Fungi , Phosphate solubilization ,Phosphorus , Acid phosphatase , Halo zone , A vailable phosphorus ,PSMs , TCP, Maize , Pearl millet , bio-fertilizer ,poultry manure , Optimization.