Effects of bio, mineral nitrogen fertilizer management, under humic acid foliar spraying on fruit yield and several traits of eggplant (Solanum melongena L.)

To study the effect of nitrogen fertilizer and foliar spraying of humic acid on yield and yield components of eggplant, an experiment was conducted in factorial format based on randomized complete block design with three replications in Astaneh Ashrafiyeh (north of Iran) during 2011 farming year. Factors of experiment consist of humic acid foliar spraying in three levels; H1: control (without humic acid spraying), H2: 25 mg/L and H3: 50 mg/L, and nitrogen fertilizer management with six levels; N1: control (no nitrogen and no nitroxin), N2: 40 kg/ha pure nitrogen, N3: 80 kg/ha pure nitrogen, N4: roots inoculation with nitroxin, N5: 20 kg/ha pure nitrogen +roots inoculation with nitroxin and N6: 40 kg/ha pure nitrogen + roots inoculation with nitroxin. At maturity, fruit yield, number of fruits per square meter, number of branches per plant, plant height, fruit length and fruit width were measured. Results showed that, the effect of foliar humic acid spraying on all measured traits had significant differences at 1% probability level. Also, effect of nitrogen fertilizer management on fruit yield, number of fruit per square meter, plant height, fruit length and fruit width at 1% and on number of branches per plant at 5% was significant. Interaction effect of foliar humic acid spraying and nitrogen fertilizer management on fruit yield at 1% and on number of fruit per square meter, plant height, fruit length and fruit width at 5% was significant and on number of branches per plant was non significant. The highest fruit yield was obtained from use of 50 mg/L humic acid spraying and also from 80 kg/ha nitrogen fertilizer.   Key words: Eggplant, nitrogen, humic acid, yield, Iran.