INTERACTIVE EFFECTS OF ZINC AND DIFFERENT NITROGEN SOURCES ON YIELD AND QUALITY OF ONION

and 2003 to investigate the interactive effect of Zn and different nitrogen sources, i.e., mineral nitrogen (ammonium sulfate) and organic nitrogen (poultry manure) on the growth and productivity of onion (Allium cepa) cv. Giza 20. Four levels of Zn application (0, 1, 2 and 3 ppm) in a sulfate form were foliar sprayed at 30 and 60 days after planting. Within each Zn application, three treatments of nitrogen dose were applied in different combination forms (mineral and organic sources). Nitrogen treatments were 100% mineral N; 75% mineral + 25% organic and 50% mineral + 50% organic. Organic-N source was poultry manure. All poultry manure treatments were applied during soil preparation. Data showed that all growth parameters of onion plants increased as the fraction of poultry manure increased. Zn had also a positive effect on all plant parameters except of plant length, and leaf dry weight. The interactive effect of Zn and poultry manure increased yield and quality of onion bulbs. The most effective treatments on bulb fresh weight, total yield and quality were the spraying with 1 or 2 ppm zinc and the application of N as 75% mineral and 25% organic, in both season