Field trials, on rice crop ( Oryza sativa ), variety Giza 178, cultivated at EI-
Serw Agricultural Research Station, were conducted in two successive seasons (2002
and 2003). Microbial inoculation with two strains of nitrogen fixers namely Bacillus
polymyxa or Azotobacter chroococcum as well as yeast strain (Saccharomyces
cerevisiae) was applied. Effect of inoculation time (rice nursery , transplanting and
twice in the nursery and after transplanting stages) under three levels of N fertilization
(20, 40 and 60 kg N/fed) as ammomium sulfate 20.5% N were studied. Split plot with
4 replicates was designed. Plant ;,eight, number of productive tillers, panicle length
and weight and 1000-grain weight were recorded. Grains and straw yields were also
measured. Nitrogen and phosphorus contents and uptake of grains and straw were
determined. Microbial incculatlon of nursery and transplanting str--ges revealed a
positive signifi~nt effect on both yield and plant growth parameters in the presence of
two thirds and full recommenced dose of nitrogen in comparison with other
treatments. Utiliz!ng PGPR inoculation in rice cultivation can save about 2G kg
N/fedd,m, which is very important from economical pcint of view. The highest Nand P
contents and uptake in beth rice grain anc straw resulted from the diazctrophs
inoculation under using 60 kg N/fed. Similar response was detected with yeas!
inoculation except nitrogen content of grains. If plant growth promoting rhizobacteria
(PCPR) .nocul ..• tion tec!';nolcgy introduced to even 50% of the rice cultivated area in
Egypt, it may result in saving about 10.000 tons of nitrogen element and conserve
environment 1:1 reducing pollution hazards,