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Abstract
This work based on two principal points, the first was to isolate the cyanobacteria isolates from different Egyptian rice soils at different governorates, i.e., Damietta, El- Sharkia and Kafr El- Sheikh. The isolated cyanobacteria isolates were then identified and tested for their nitrogen fixing ability and thereafter, the most efficient nitrogen fixing ones were used in the preparation of the cyanobacterial soil based inoculum. The second point was a pot experiment which carried out in the greenhouse at Sids Agric. Res. Station, Agric. Res. Center, Beni Suef Governorate to study the effect of cyanobacteria inoculation and nitrogen fertilization on rice productivity. The most important results can be summarized as the following:
1- Nineteen cyanobacteria isolates were isolated from the rice soils
2- Ten cyanobacteria strains were nitrogen fixing non-branching filamentous heterocystous, only one of them was having true branching (Haplosiphon hibernicus) and two were unicellular (Aphanocapsa pulchra and Chroococus minutus). Seven strains were belonged to Kafr El- Sheikh Governorate all of them were nitrogen fixing non-branching filamentous heterocystous. Two cyanobacteria strains belonged to El- Sharkia Governorate and they were nitrogen fixing non-branching filamentous heterocystous.
3- At 30 days after rice transplanting, the use of cyanobacteria + 50% N dose was comparable with the use of 100% N dose, since both treatments showed not significantly different values of NP & K- plant uptake.
4- At 30 days after rice transplanting, the use of cyanobacteria + 50% N dose was comparable with the use of 100% N dose., since both treatments showed not significantly different values of soil available N,P & K.
5- At 30 days after rice transplanting cyanobacteria inoculation enhanced the soil biological activity in terms of CO2 evolution, nitrogenase and dehydrogenase activities and both total bacteria count and total N2-fixing cyanobacteria count compared either to the control or the treatments received 25, 50 and 100% N dose alone.
7- At harvest the use of cyanobacteria + 50% N dose was comparable with the use of 100% N dose, since both treatments showed not significantly different values grain and straw yield, while no definite trend was observed for both 1000- grain weight and /or harvest index per cent.
8- Same trend for cyanobacteria inoculation against NP & k uptake for rice crop at harvest but the values was higher than those recorded at 30 days after rice transplanting.
9- Both soil available NP & K and soil biological activity increased in the remained soil after rice harvesting in response to cyanobacteria inoculation but the values was less than those attained at 30 days after rice transplanting.