Optimizing rapeseed (Brassica napus L. var.oleifera) yield, nutritional profile, andfunctional traits: dominant role of seasonalconditions and fertilization strategy overcultivar effects

Abstract

BACKGROUND: Rapeseed (Brassica napus L. var. oleifera) is a globally significant vegetable oilseed crop. Its seeds are sources ofoil and protein for industrial applications and food. This study shows how rapeseed cultivar, and environmental and fertiliza-tion 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, andtemperature trends. In 2020/21, earlier sowing (6 October) and higher precipitation during flowering (56 mm in April), resulted in agrain yield of 2.16 Mg ha−1, whereas delayed sowing (21 October), reduced rainfall (−52% in April), and higher temperature (+4.2 °Cduring vegetative growth) in 2022/23 caused a 79% yield decline. Higher nitrogen rates (140 and 190 kg N ha−1) increased the drybiomass at flowering and the grain yield at harvest, with intermediate rates (110 kg N ha−1), achieving comparable results to higherrates by optimizing timing, particularly in pre-sowing and early spring. Nitrogen fertilization also significantly impacted fatty acidcomposition and accumulation of polyphenols, with higher nitrogen rates related to increased levels of specific fatty acids. Phenoliccompounds analysis revealed significant fluctuations depending on the year, with anthocyanins, flavanols, and flavonols being themost susceptible. In 2020/21, anthocyanins were the most abundant polyphenols, whereas in 2022/23, the highest levels wereobserved for fatty acids, specifically ⊍-linolenic acid (10.9%) and eicosenoic acid (1.17%).CONCLUSION: The results highlight the importance of strategic planning, environmental monitoring, and targeted nitrogen fertilizationin optimizing rapeseed yield and quality under a changing climate, providing valuable insights for sustainable rapeseed cultivation.