Optimizing rapeseed (Brassica napus L. var. oleifera) yield, nutritional profile, and functional traits: dominant role of seasonal conditions and fertilization strategy over cultivar effects

BACKGROUND Rapeseed (Brassica napus L. var. oleifera) is a globally significant vegetable oilseed crop. Its seeds are sources of oil and protein for industrial applications and food. This study shows how rapeseed cultivar, and environmental and fertilization conditions influence the agronomic parameters, fatty acid composition, and polyphenol content of rapeseed.RESULTS Seasonality was the factor affecting grain yield the most, with variations attributed to sowing dates, rainfall patterns, and temperature trends. In 2020/21, earlier sowing (6 October) and higher precipitation during flowering (56 mm in April), resulted in a grain yield of 2.16 Mg ha-1, whereas delayed sowing (21 October), reduced rainfall (-52% in April), and higher temperature (+4.2 degrees C during vegetative growth) in 2022/23 caused a 79% yield decline. Higher nitrogen rates (140 and 190 kg N ha-1) increased the dry biomass at flowering and the grain yield at harvest, with intermediate rates (110 kg N ha-1), achieving comparable results to higher rates by optimizing timing, particularly in pre-sowing and early spring. Nitrogen fertilization also significantly impacted fatty acid composition and accumulation of polyphenols, with higher nitrogen rates related to increased levels of specific fatty acids. Phenolic compounds analysis revealed significant fluctuations depending on the year, with anthocyanins, flavanols, and flavonols being the most susceptible. In 2020/21, anthocyanins were the most abundant polyphenols, whereas in 2022/23, the highest levels were observed for fatty acids, specifically alpha-linolenic acid (10.9%) and eicosenoic acid (1.17%).CONCLUSION The results highlight the importance of strategic planning, environmental monitoring, and targeted nitrogen fertilization in optimizing rapeseed yield and quality under a changing climate, providing valuable insights for sustainable rapeseed cultivation. (c) 2025 Society of Chemical Industry.