EFFECT OF NITROGEN FERTILIZATION LEVELS ON YIELD AND YIELD COMPONENTS OF DURUM WHEAT (TRITICUM DURUM DESF.)

The experiment was carried out during the winter agricultural seasons 2021/2022 at two locations in Mosul (Bashiqa and Balawat) to study the response of five durum wheat varieties (Duma, Gigamor, Maggi, Sardar, Zeina2) to three levels of nitrogen fertilizer (88, 174 and 264 kg/ha) applied as of urea 46% N for traits, flowering date, 1000 grain weight, number of spikes/ 1 m(2), number of grains/10 spikes, harvest index and grain yield using Randomized complete block design with a split plots system with three replications. The combined analysis of variance result showed significant differences between locations for flowering date, number of spikes per plant and harvest index, between varieties for all studied traits and between nitrogen fertilizer levels for for all traits except for the flowering date. The variety Zeina2 surpassed others for most traits including grain yield except flowering date followed in importance by Sardar variety. The level of nitrogen fertilizer 264 kg/ha surpassed for all traits according to Duncan's Multiple Range Test, but it was found through the results of trend analysis that the best levels of nitrogen fertilizer was 88, 183.75, 171.75, 134.99, 264.0 and 211.63 kh/ha for flowering date, 1000 grains weight, number of spikes per plant, number of grains per spike, harvest index and grain yield respectively, whereas, the appropriate regressive relationship for fertilizer levels was of first degree (linear) with flowering date and harvest index and of second degree (squared) with other traits. From combination between locations, varieties and nitrogen fertilizer levels it turns out that variety Zeina2 at the level of 264 kg/ha of nitrogen fertilizer in Balawat location had a good performance for most of studied traits, including grain yield.