Effect of Times and Levels of Nitrogen Fertilization on the Characters of Vegetative Growth, Flowering and the Yield of Summer Squash (Cucurbita pepo L.) c.v. Mullah ahmad

This study was conducted at the vegetable field of department of horticulture and landscape design, college of agriculture and forestry ,Mosul university, during spring of 2007 and 2008, to study the effect of times and levels of nitrogen fertilization on some characters vegetative growth, flowering ,and yield of summer squash .Result indicated that, the time of nitrogen fertilization at the stage of fruit-set caused a significant increased in the leaf number /plant ,length of the plant and the fresh weight/plant. While the time of nitrogen fertilization wasn't affected significantly the total yield. The level at 320 kg.N/ha caused a significant increase of the characters vegetative growth and total yield. Also result revealed that, the interaction between the stage at fruit set and nitrogen fertilization at 320 kg.N/ha led to increase the total yield .The yield was found to positively correlation with the plant length ,fresh and dry weights of plant, leaf area, fruit weight, male and female flowers, and the sex ratio.