Two field experiments were carried out during the two successive winter
seasons of 1999/2000 and 2000/2001 at the experimental farm. Faculty of Agriculture,
Alexandria University in Damanhour, El-Behira govemorate. The objectives of this
investigation was to study the main effects of Six N fertilizer levels (0, 18, 36, 54, 72
and 90 kg N fed") and three different biofertilizer types Microbein (a mixture of
Azotobacter, Azospirillum , Pseudomonas, Rhizobium and Bacillus), Rhizobacterin (
a mixture of Azotobacter and Azospirillum) and Halex-2 (a mixture of Azotobacter,
Azospiillum and Kebsiella) as well as their interaction on vegetative growth characters
,leaf chlorophyll contents and N content of storage leaves of onion (Allium cepa L.) cv.
Giza 20. The obtained results indicated that application of mineral N, significantly
increased plant length, plant fresh weight, leaves fresh weight plant", leaves dry
weight plant" and I eaves d ry matter percentage over the untreated plants, in both
seasons. Meanwhile application of N fertilizer irrespective of the level used, did not
affect number of leaves plant". The highest two N rates 72 and 90 kg N fed" were
remarkable and associated with the highest mean values for the most studied
characters, but the differences between them were not found significant. Mean values
of all the studied growth characters except leaves number, showed significant
increments with the inoculated plants comparing with untreated ones. Moreover,
Halex-2 application 0 f I he b iofertillzer r ellected the highest mean values r or a II the
stcdled growth parameters, leaves chlorophyll content and storage leaves N content.
Fertilization of onion plants with 72 or 90 kg N fed·¹ combined with Halex-2 was the
best interaction treatment for all the growth parameters.