Yield and quality of winter oilseed rape in response to different systems of foliar fertilization

The aim of this study was to determine the effect of different systems of foliar fertilization on the yield of winter oilseed rape (Brassica napus L.), the mineral composition of post-harvest biomass and the processing suitability of seeds. In winter oilseed rape grown on boulder clay, intensified foliar fertilization increased seed yield (by 0.43-0.69 Mg ha-1 87% dry matter, DM), straw yield (by 0.59-1.69 Mg ha-1 DM), and decreased the harvest index (by 2-3%). The seeds of winter oilseed rape accumulated more N, P, Ca, Zn, Cu, Mn and Fe than straw. The concentrations of P, Mg and S were higher in straw than in seeds. Foliar fertilization increased the N, P and K content (by 2.0, 0.35 and 1.15 g kg-1 DM, respectively) and decreased the Mg and S content of straw (by 2.08 and 0.77 g kg-1 DM, respectively). A chemical analysis of seeds revealed significant changes only in the concentrations of K, S (increase by 0.57 and 0.55 g kg-1 DM, respectively) and P (decrease by 0.90 g kg-1 DM, respectively) under the influence of foliar fertilization. Intensified foliar fertilization increased the concentrations of Cu and Zn and decreased the levels of Mn and Fe in straw and seeds. The nutritional value of seeds deteriorated (crude fat content decreased by around 5.5 g kg-1 DM, but the composition of fatty acids (FAs), and the proportions of saturated FAs, monounsaturated FAs and polyunsaturated FAs were not significantly altered) with an increase in foliar fertilization levels. Foliar application of macronutrients and micronutrients improved the feed value of winter oilseed rape seeds. Intensified foliar fertilization reduced the content of alkenyl (by approx. 47%) and indole (by approx. 6%) glucosinolates in seeds, mostly due to a decrease in the concentrations of progoitrin, gluconapin and 4-OH-glucobrassicin.