Depending on soil nitrogen availability and soil–climatic conditions, nitrogen application at the boot stage in wheat can help maintain the photosynthetic activity of the upper leaves and support grain development and filling, thereby contributing to increased yield and protein content. This study examined the impact of nitrogen applied at the booting stage on grain yield, protein content, grain N uptake, and nitrogen use efficiency (NUE) of common winter wheat (Triticum aestivum L.) in Transylvanian Plain conditions. The experiment included eight consecutive crop seasons (2018–2026), four varieties (Andrada, Codru, Luminiţa, Georgiana), and two nitrogen doses: N₅₀ and N₁₀₀. In the N_50- fertilization variant, 50 kg ha⁻¹ nitrogen active substance was applied in autumn before sowing as basic fertilization and in the variant N_100-, and other 50 kg ha⁻¹ nitrogen was applied at the booting stage in addition to the base fertilization. The results showed that the additional fertilization of 50 kg N ha⁻¹ at the booting stage, on top of the 50 kg N ha⁻¹ applied before sowing, increased grain yield by an average of 763 kg ha⁻¹ and grain protein content by 2.24 percentage points compared with the basic fertilization treatment (N₅₀). The magnitude of the response varied among growing seasons and wheat genotypes. The calculated nitrogen use efficiency values also varied across genotypes and crop season, reflecting differences in crop response under the tested fertilization treatments. Since the experiment did not compare alternative nitrogen application timings at equivalent total nitrogen rates, the results should be interpreted specifically in relation to the additional nitrogen treatment evaluated in this study.

This study aimed to investigate the effects of different nitrogen (N) fertilizer rates and sowing dates on grain yield, protein content, grain N uptake, and nitrogen recovery efficiency (NRE) in spring and facultative wheat (Triticum aestivum L.) cultivated in northwestern and central Romania from 2018 to 2020. The experiment was designed as a split–split plot study with two spring sowing dates (SDs): an optimal date (1–15 March) and a delayed date (postponed by two weeks). All treatments received a basal autumn fertilizer supplying 36 kg N ha⁻¹ and 92 kg P ha⁻¹. In spring, three N treatments were evaluated: no additional N (N₃₆), 72 kg N ha⁻¹ (N₁₀₈), and 105 kg N ha⁻¹ (N₁₄₁), with the supplementary N top-dressed at the booting stage. The results showed that delayed sowing significantly altered grain N uptake dynamics and reduced NRE, even under standard fertilization regimes. Specifically, delayed sowing reduced grain yield by 7.52% to 28.39% compared to optimal sowing, while adverse climatic interactions in delayed setups reduced the mean NRE to as low as 16.43%. These findings indicate that conventional N application strategies may be suboptimal under variable sowing conditions and highlight the importance of adaptive N management to improve both agronomic performance and environmental sustainability.

This study examined the impact of nitrogen applied at booting stage on grain yield, protein content, grain N uptake, and nitrogen recovery efficiency (NRE) of common winter wheat (Triticum aestivum L.) in Transylvanian Plain, in the period 2019-2026. The experiment included eight consecutively years, four varieties and, two nitrogen doses: N50 and N100. In the variant of fertilization N50, 50 kg ha-1 nitrogen active substance were applied in autumn before sowing as basic fertilization and in the variant N100, other 50 kg ha-1 nitrogen were applied at the booting stage in addition to the base fertilization. Our research has shown that, compared to other wheat growth stages, applying nitrogen at the booting stage (one week before heading) significantly improved yield and protein content. Nitrogen applied at the booting stage conducted to an increase of yield by an average of 763 kg ha⁻¹ and in grain protein content by 2.24%. The NRE values for all the studied varieties indicate an efficient utilization of nitrogen fertilizers applied at the booting stage, except the years marked by drought in May, such as 2019/2020 or when drought from June is accompanied by scorching heat, such as 2023/2024.