Résumé:
The proper and sustainable management of nitrogen fertilization is one of the most
common problems of cereal cultivation in semiarid regions, which are characterized by a wide
variability in climatic conditions. The current work was conducted to evaluate the effects of
nitrogen fertilization on the agronomic and economic aspects of durum wheat cultivated under
rainfed semiarid conditions in Algeria and to determine the most efficient nitrogen use
efficiency (NUE) among seven genotypes that are widespread in the country (tall and short,
old and modern genotypes), and to evaluate the effect of weather conditions (the total rainfall
at vegetative period, the total rainfall at flowering and filling period and the mean
temperature) on grain yield and NUE under two contrast environments (Algeria and Italy) .
The seven genotypes, Bousselam, Waha, MBB, Sétifis, Megress, Massinissa and
Gtadur were investigated under four nitrogen rates from 0 to 120 uN ha-1 during three
cropping seasons (2016 to 2019). The results indicate that the total nitrogen uptake at maturity
(NM), nitrogen uptake by grain (NG), nitrogen harvest index (NHI), NUE and its
components, such as nitrogen uptake efficiency (NUpE) and nitrogen utilization efficiency
(NUtE), were significantly affected by year, genotype, and nitrogen level.
From this study, it appears that higher nitrogen rates improved NM and NG. However,
no effects on grain yield were observed; conversely, increased nitrogen levels produced a
12% reduction in the economic return. In other words, in the North African environment, the
response to nitrogen is more evident in quality than in yield, which in turn is dependent on the
yearly weather conditions and cultivated genotypes. Moreover, nitrogen negatively affected
NUE and its components (NUpE, NUtE). On average, NUE displayed low values (14.77 kg
kg-1), mostly irregular and highly dependent on weather conditions; in the best year, it did not
exceed 60% (19.87 kg kg-1) of the global average value of 33 kg kg-1. Moreover, the modern
genotypes Megress (tall) and GTAdur (short) showed the best capacity to tolerate different
nitrogen conditions and water shortages, providing relatively superior yields, as well as more
effective N use from fertilizers and the soil than the other two genotypes.
The total rainfall at the vegetative period (RVP) had the most significant effect on both
grain yield and nitrogen use efficiency (NUE). Adequate rainfall during this phase improved
N uptake efficiency (NUpE) and N utilization efficiency (NUtE), leading to higher NUE
