INFLUENCE OF SOME NITROGEN FERTILIZATION RATES AND APPLICATION METHODS ON GROWTH, YIELD AND YIELD COMPONENTS OF ONION

This investigation was conducted at Sids Agricultural Research Station, Bani-Swief Governorates, during two seasons of 2012/2013 and 2013/2014, to evaluate the effect of six nitrogen treatments (60 kg N without starter fertilizer, 60 kg N with starter fertilizer, 90 kg N without starter fertilizer,90 kg N with starter fertilizer, 120 kg N without starter fertilizer and 120 kg N with starter fertilizer) and three application methods (broadcasting, side dressing and top dressing) on vegetative growth characters, yield and yield components as well as quality and storability of onion.The obtained results could be summarized as follow:
• The obtained data revealed that plant height, No. of leaves/plant, bulb diameter, bulb length, bulb weight and No. of days to maturity were significantly affected by nitrogen dose in both seasons.
• Adding the highest nitrogen dose of 120 kg N with starter fertilizer gave the highest values of plant height, No. of leaves per plant, bulb diameter, plant weight and No. of days to maturity in both seasons.
• Adding of nitrogen by top dressing method appeared the largest values in respect to all vegetative growth characters, except for bulb diameter in the first season.
• Nitrogen dose significantly affected bulb weight, total yield/fed., marketable yield/fed.and culls yield in both seasons.
• The highest values of bulb weight, total yield and marketable yield were obtained under nitrogen dose of 120 kg N with starter fertilizer in both seasons.
• Application of nitrogen fertilizer by top dressing methods achieved the maximum values of bulb weight, total yield and marketable yield in both seasons.
• Adding of 120 kg N/fed. with starter fertilizer achieved the maximum values of TSS% in both seasons and dry matter % in the second season.
• The largest values of TSS% and dry matter % were obtained by adding nitrogen fertilizer by top dressing method in both seasons.
• After storing for two months the lowest values of weight loss % were observed under nitrogen dose of 60 kg N/fed. without starter fertilizer, in both seasons.
• Application of nitrogen by top dressing appeared the lowest values of weight loss% after storing for 2, 4 and 6 months in both season.
• Based on the current experimental results, with regards to the production as well as economic analysis, application of 120 kg N/fed. with starter fertilizer by top dressing method may be suggested for maximizing onion production
under similar conditions of this work and further investigations are needed to be conducted in other agro ecological zones of Egypt.