The hypothesis that seed inoculation -vith the N-fixing bacteria: Azotobacter
ctucococcum and Azospiril/um brasilense cou d reduce the meniral N requirements
fer early and late sown cotton plantings was tested at the experimental farm of
II/allawi Agric: Res. Station, Agric. Res. Center, Minia. Egypt, during 2002 and 2003
Seasons, using Giza 83 cotton cultivar. Seed bacterial inoculation was combined with
five \ raded rates of chemical N; 0, 15, 30, 45 and 60 kgN/fed., while the control
treatment was 60 kgNlfed. without bacterial inoculation, The obtained results from that
study could be summarized as follow: Delaying cotton sowing tended to give taller plants with longer internodes,
but it markedy reduced most of yield compor ents and seed cotton yield/fed. While
sowing date had no effect on leaves content of chlorophyll. Across planting dates, reducing the chemical N rate to be 0 or 15 kgN/fed. at
earlv sowing, even with seed bacterial inoculation, significantly reduced leaves
content of chlorophyll, most of growth parameters and yield components, and seed
cotton yield/fed. However, with seed inoculation with N-fixing bacteria, leaves content
of chlrophyll a, b and total chlorophylls as well as seed cotton yield per fed. were not
significantly reduced with decreasing the meniral N rate to 45 kgN/fad., and all studied
growth parameters and yield components were not significantly reduced with reducing
the mineral N rateto 30 kgN/fad. at late sowing. The interactlon of planting date X N hac significant effects on leaves content
of total chlorophyll, number of open bolls/plant, and seed cotton yield/fad. as :h~
reduction in these traits due to reducing the rneniral N rate under early planting da>
was higher than under late one. It could be concluded from this study that due to inocutation of cotton seed
with N-fixing bacteria, the chemical N rate could be decreased to 45 N/fad. for early
planting and to 30kgN/fad. for late planting without significant reduction in seed cotton
yield, saving at least 15 kg/fad. from the recommended mineral N rate, reducinq the
costs of meniral N fertilizers and environmental pollution at the same time.