Response of winter rape (Brassica napus L. ssp. oleifera Metzg., Sinsk) to foliar fertilization and different seeding rates

A field experiment in growing winter rape was carried out during the period 2009-2011 in a family farm (owned by Mr. M. Bednarczyk) located in Jaroszewice (Lublin region), on podzolic soil. Plant biometric features as well as yield and seed qualitative parameters (oil, protein and glucosinolate content) were evaluated depending on the following rates of soil NPK fertilizers and on foliar fertilization (autumn spraying with the fertilizer solution): 100% and 75% of NPK as well as urea + nickel chelate + MgSO4H2O; 100% and 75% of NPK as well as urea + Plonvit R + MgSO4H2O). Plots without foliar fertilization (only 100% of NPK) were the control treatment. The other experimental factor was the seeding rate (2.5 kg×ha-1 – 30 cm row spacing; 4 kg×ha-1 – 18 cm row spacing). Foliar spraying was done once in the autumn in the second decade of October. Tillage as well as mechanical and chemical control of agricultural pests in the plantation were typical for this plant species and consistent with the recommendations for winter rape protection. A hypothesis was made that the application of foliar fertilizers would have a beneficial effect on winter rape productivity, at the same time maintaining the high quality of raw material. It was also assumed that a reduction in the seeding rate of winter oilseed rape would result in reduced plant lodging and an increased number of siliques per plant; as a consequence, seed and oil productivity would be at a level not lower than that obtained at the higher seeding rate. The present study has proved that foliar fertilization of winter oilseed rape in the autumn period contributes to improved plant winter hardiness and increased productivity. The application of foliar fertilizers also enables the rates of basic mineral NPK fertilizers to be reduced by 25% without detriment to seed yield. Foliar fertilizers have been found to have a weaker effect on changing the chemical composition of rapeseed. The study has shown that, from the productive point of view, it is justified to use the lower seeding rate (2.5 kg×ha-1), since winter rape yield (seed and oil yield) did not significantly differ from that found in the case of the higher seeding rate (4.0 kg×ha-1).