Yield, nitrogen use efficiency and grain quality in durum wheat as affected by nitrogen fertilization under a mediterranean environment

Limited information is available concerning the influence of nitrogen fertilization jointly on yield response, nitrogen use efficiency (NUE) and grain quality of durum wheat under semi-arid Mediterranean conditions. The study focused on evaluating, through a systematic study, over three seasons in southern Italy the effects of three nitrogen fertilization rates (0, 80 and 160 kg N ha^-1 - N<inf>0</inf>, N<inf>80</inf> and N<inf>160</inf>), on grain yield, yield components, nitrogen efficiency indices and grain quality characteristics of three durum wheat genotypes ('Creso', 'Trinakria' and 'Line 25') from different breeding eras to achieve a more sustainable fertilization management of the durum wheat crop. We found that nitrogen fertilization at 80 kg N ha^-1 was able to maximize the yield performances (2.1 t ha^-1 year^-1) of the crop and keep NUE index at an acceptable level (16.3 kg kg^-1). On the other hand, nitrogen fertilization at 160 kg N ha^-1 improved grain quality measured through protein (up to 14.3%) and dry gluten concentration (up to 12.8%), but had a detrimental effect on grain yield and nitrogen efficiency. Among the genotypes studied, 'Trinakria' showed the greatest potential to utilize nitrogen fertilization to improve grain yield and NUE (at N<inf>80</inf>) and quality (at N<inf>160</inf>), 'Line 25' made good use of N<inf>80</inf> both for yield and quality, whereas 'Creso' proved wholly unresponsive to nitrogen. The effect of N fertilization on grain yield and N use efficiency depends on rainfall distribution, giving the best results when about 80% of total rainfall occurred from sowing to heading. Overall, our data show that in seasons with regular rainfall in quantity and distribution, combining no more than 80 kg ha^-1 of nitrogen fertilization with genotypes characterized by a more efficient response to nitrogen, is a useful tool to improve the agronomic and quality performance of the crop, ensuring, at the same time, a more environment-friendly nitrogen fertilization.