Synergistic effects of magnesium and zinc supplementation on yield performance and oil quality of canola (<i>Brassica napus</i> L.) in reclaimed soil environments

Abstract Canola ( Brassica napus L.) is an important oilseed crop with notable economic and nutritional value; however, its productivity in newly reclaimed soils is hindered by nutrient deficiencies and complex soil conditions. This study examined the combined effects of magnesium (Mg) fertilisation and zinc (Zn) foliar applications on the growth, yield and oil quality of canola in newly reclaimed soils in Egypt during the 2021/2022 and 2022/2023 growing seasons. A split-plot experimental design was utilised, featuring Mg rates (12, 24, 48 and 72 kg/ha) as main plots and Zn foliar applications (0, 3, 5 and 6 g/L) as sub-plots. The results indicated significant improvements in plant growth characteristics, yield components and oil parameters with elevated levels of Mg and Zn. The treatment combination of 72 kg Mg/ha and 6 g/L Zn consistently improved plant height, number of primary branches, siliques per plant and 1000-seed weight in both seasons. Seed yield increased by 71%, achieving 3.50 t/ha, while oil yield exhibited a 134.9% rise, reaching 1,377.43 kg/ha. Principal component analysis revealed that the increased application of Mg and Zn significantly enhanced agronomic performance, with the first two principal components accounting for 90.7% of the total variance. Correlation and path analyses revealed intricate interactions among traits, with the number of siliques per plant and oil content demonstrating the most significant direct effects on seed and oil yields. This study highlights the significance of balanced nutrient management for optimising canola productivity.