EFFECT OF TIME NITROGEN FERTILIZER APPLICATION ON THE SENESCENCE AND GRAIN YIELD OF FIVE DURUM WHEAT CULTIVARS (TRITICUM DURUM DESF.)

The experiment was conducted to evaluate the effects of time nitrogen fertilizer application on the senescence of durum wheat and its association with grain yield and its components. The experimental treatments were set up in a split-plot design with five durum wheat cultivars (Adnham, Grecale, Duma, Sardar, Svevo) as the main plots and the time nitrogen fertilizer application (100 % tillering, 100 % stem elongation and 50% tillering + 50 % stem elongation stages) under two locations in Northern Iraqi conditions. The results of this study indicate that late senescence cultivars (Grecale and Svevo) produced the highest flowering date, No head/m2, No. grain/10 head, grain yield g/m2 and harvest index %. Moreover, time nitrogen fertilizer application at the tillering stage (early application) influenced most of the studied traits. In conclusion, extending photosynthesis capacity during the grin-filling phases by delaying the rate of senescence might be a good approach to improve grain yield of wheat cultivars.