Effect of Different Levels of Nitrogen and Potassium Fertilizers on Grain Yield and Quality Properties of Two Durum Wheat [Triticum turgidum L. ssp. durum (Desf.) Husn.] Cultivars

To study the effect of different levels of nitrogen and potassium fertilizers on grain yield and quality properties of durum wheat cultivars, a field experiment was carried out in the research filed of the Seed and Plant Improvement Institute in Karaj, Iran, in 2019-20 and 2020-21 cropping seasons. Split plot arrangements in randomized complete block design with three replications was employed to assess the effect of nitrogen and potassium fertilizers levels on grain yield and quality properties of two durum wheat cultivars. Two durum wheat cultivars (Hana and Sana) were assigned to main plots, and different levels of urea and potassium sulfate fertilizers (control, 200, 300, 400 kg ha-1 urea (N) and each level of nitrogen fertilizer with 100 and 200 kg.ha-1 potassium sulfate (K)) were randomized in sub-plots. The results showed that the effect of year and different fertilizer levels on grain yield was significant (P ≤ 0.01). The grain yield increased by increasing nitrogen and potassium fertilizer levels. It was notable that the simultaneous application of these two fertilizers showed greater effect on grain yield. Therefore, grain yield at 300 kg ha-1 of urea fertilizer plus 200 kg ha-1 of potassium sulfate fertilizer was higher than sole 400 kg ha-1 urea fertilizer. Quality properties included; hectoliter weight, grain protein content, zeleny sedimentation volume, grain hardness index, grain wet gluten content, gluten index, SDS sedimentation height, semolina extraction rate and grain yellow berry percentage. The combined analysis of variance showed that there was significant differences among different fertilizer levels for all grain quality properties, and between years for wet gluten content, grain hardness, semolina extraction rate and grain yellow berry percentage. Wet gluten content, grain hardness and semolina extraction rate in 2019-20 were higher than in 2020-21 cropping season. Whereas, grain yellow berry percentage was higher in 2020-21 cropping season. In General, increasing the rate of fertilizers application increased all quality properties except grain yellow berry percentage that decreased by 76% at 400 kg ha-1 urea plus 200 kg ha-1 potassium sulfate as compared with control. It is concluded that application of 400 kg ha-1 urea plus 200 kg ha-1 potassium sulfate could be sufficient for optimizing grain yield and quality properties of durum wheat in Karaj region.