الفهرس 
Agricultural Importance of Cyanobacteria.Only 14 pages are availabe for public view
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Abstract
Samples of two different soils were collected from the surface crust of El- Ismailia Research Station (sandy soil) (El- Ismailia Governorate) and Sids Res. Farm (alluvial clay loam soil) (Beni Swef Governorate), Agric. Res. Center, Giza Egypt. The soil samples were used for isolation of some cyanobacteria agents. The isolated cyanobacteria were purified and identified. Such cyanobacterial strains were identified as Nostoc muscorum, Nostoc commune. Nostoc linckia, Nostoc elloipsosporum, Anabaena variabilis and Anabaena orientalis. The identified cyanobacterial strains were then used to carry out some laboratory examinations and greenhouse experiment as followis: Laboratory Examinations 1- Evaluation of the ability of two cyanobacterial strains singly mixted to colonize the roots of 15-day old wheat seedlings.
2- Declaring the effect of both NaCl and phosphate on growth and nitrogen fixing ability of the isolated cyanobacterial strains. Greenhouse Expriments Studying the effect of cyanobacterial inoculation combining with varying nitrogen rates on the growth and N, P & K contents of wheat plants, as well as, the nitrogen use efficiency, at two sampling periods, i.e., 30 and 65 days after sowing. The experiment included the following aims to be declared: 1. Effect of cyanobacterial inoculation on nitrogen fixing efficiency (nitrogenase activity) in wheat soil rhizosphere.
2. Effect of cyanobacterial inoculation on soil contents of available N, P & K. 3. Effect of cyanobacterial inoculation on the soil rhizosphere biological activity in terms of dehydrogenase activity, carbon dioxide evolution. The obtained results can be summarized in the following:
A) Growth Biomass and Nitrogen Fixing Efficiency of the Isolated Cyanobacterial Strains Increasing the incubation period up to 5 weeks under continuous illumination increased both biomass production and nitrogenase activity for all isolated strains with priority of both Nostoc muscorum, Anabaena variabilis and N. linckia. - NaCl enhanced the growth and nitrogen fixation power of the isolated cyanobacterial strains up to 8000 ppm, after which they started to decline when exposed to higher NaCl concentration of 12000 ppm with priority to Nostoc muscorum, which seemed to tolerate high salinity. - Cyanobacterial cultures supplemented with P up to 60 mg P l-1 were characterized by high values of biomass yield and could fix more N2 as compared with the other ones supplied with limited levels of P. Raising phosphorus level in growth medium up to 100 mg P l-1 suppressed, to some extent, the dry weight and nitrogenase activity of all cyanobacterial strains at all the incubation periods. B) Effect of Cyanobacterial Inoculation on Wheat Plants
- Inoculation with cyanobacteria to wheat plants significantly increased the wheat plant dry weight at both tested periods and soils, compared to the control treatments without any addition. - Both nitrogen additions and cyanobacterial inoculation increased the N, P & K uptake by wheat plants grown on either soil and at both tested growth periods. Also, the values of N, P & K taken up by wheat plants in the alluvial soil were higher than those recorded for the sandy one. The treatment of 75% N + cyanobacteria gave the highest values of N, P & K contents in wheat plants, compared to other tested treatments at both growth periods. Nitrogen use efficiency by wheat plants was higher in the alluvial soil than that in the sandy one. Also, in both soils, cyanobacterial inoculation combined with lower nitrogen doses (50 and 75 % N) resulted in higher nitrogen use efficiency by wheat plants, compared to those shown by the recommended nitrogen rate (100% N). - Values of N2-ase activity detected in for the wheat plant rhizosphere soil in response to cyanobacterial inoculation, was higher in the alluvia soil than those recorded in the sandy soil. Likewise, the values of N2-ase activity at the second period (65 days) were higher than those scored at the first period (30 days) in both chosen soils. The highest N2-ase activity values occurred as a result of the treatment with 75 % N + cyanobacteria compared to those recorded by any of 100 % N or 50 % N + cyanobacterial treatments.
- Contents of the soil available N, P & K recorded for the alluvial soil were higher than those attained by the sandy soil at both wheat growth periods. Also, in both tested soils, values of the soil available N, P & K obtained in at 65 days were higher than those appeared at 30 days. The highest contents of the soil available N, P.