A field experiment was conducted during the summer season of 2000-2001 at the Vegetable Research Farm of Indian Agricultural Research Institute (I.A.R.I.), New Delhi (India) to test the efficacy of three Azotobacter strains as a potential supplement to nitrogenous fertilizer in improving growth and yield of onion cv. Pusa Madhvi. The treatments consisted of factorial combination of four levels of nitrogen (0, 25, 50 and 75 kg N/ha) and three Azotobacter strains (CBD-15, AS-4 and M-4) with two uninoculated controls one with full dose of N (100 kg/ha) and the other without NPK. Application of 75 kg N/ha along with inoculation of CBD-15 was found to have significantly increased most of the growth and yield parameters, soil available nitrogen, and nitrogen content in the bulb followed by M-4 inoculation as compared to application of full dose of nitrogen without the inoculation. Days to bulb initiation were significantly reduced due to inoculation with CBD-15 or M-4 along with 50 kg N/ha whereas days to bulb maturity were significantly reduced due to inoculation with any of the strains along with the same N rate (50 kg/ha) as compared to application of full dose of nitrogen without the inoculation. The finding demonstrated a saving of 50 kg N/ha without significantly affecting yield and an average increase of 13.5% marketable yield due to Azotobacter inoculation in the presence of 75 kg N/ha. V letih 2000-2001 je bil na Vegetable Research Farm, Indian Agricultural Research Institute (I.A.R.I.), New Delhi (India) izveden poskus za preverjanje učinkovitost treh sojev Azotobacter kot mo_nih dodatkov k uporabi du_ičnih gnojil, da bi se izbolj_alo rast in pridelek pri čebuli cv. Pusa Madhvi. Poskus je vključeval faktorske kombinacije _tirih ravni preskrbljenosti z du_ikom (0, 25, 50 and 75 kg N/ha) in tri genotipe Azotobacter (CBD-15, AS-4 and M-4), z dvema neinokuliranima kontrolama, od tega eno z odmerkom N (100 kg/ha) in drugo brez gnojenja z NPK. Aplikacija 75 kg N/ha je skupaj z inokulacijo CBD-15 dala pomembno povečanje večine parametrov rasti in pridelka, v tleh dostopnega du_ika in vsebosti du_ika v čebulah po inokulaciji z M-4 , v primerjavi z aplikacijo polnega odmerka du_ika a brez inokulacije. _tevilo dni do začetka tvorbe čebul je bilo značilno manj_e pri inokulaciji z CBD-15 ali M-4 , skupaj z odmerkom 50 kg N/ha. _tevilo dni do zrelih čebul je bilo značilno manj_e pri inokulaciji s katerim koli genotipom pri enakem odmerku N (50 kg/ha), v primerjavi s polnim odmerkom du_ika brez inokulacije. Ugotovitve ka_ejo prihranek 50 kg N/ha brez značilnega zni_anja pridelka. Ugotovljeno je povprečno povečanje tr_nega pridelka za 13,5% pri inokulaciji z Azotobacter-jem in odmerku 75 kg N/ha.