Sulfur application has a significant effect on the yield of oil bearing plants of the family Brassicaceae, especially when the sulfur content of soil is low. Sulfur fertilization also affects the value of plant raw materials, reflected by the concentrations of mineral and biologically active compounds in biomass. The aim of this study was to determine the effect of sulfur application to soil on the concentrations of copper, zinc and manganese in the root residues, straw and oil cake of winter and spring rapeseed. A three-year (2005-2008) field experiment was conducted at the Agricultural Experimentation Station in Bałcyny (NE Poland). In both spring and winter rapeseed, oil cake contained the highest levels of copper and zinc, followed by root residues and straw. The highest concentrations of manganese per kg dry matter (DM) were found in the root residues of winter rapeseed and in the cake of spring rapeseed. The concentrations of micronutrients (Cu, Zn, Mn) were slightly higher in the roots of winter rapeseed, compared with spring rapeseed. Sulfur fertilization decreased copper levels and increased manganese levels in the root residues of spring and winter rapeseed. Sulfur application to soil increased zinc concentrations in winter rapeseed roots, and it had no significant influence on the zinc content of spring rapeseed roots. Spring rapeseed straw contained considerably higher levels of zinc and manganese than winter rapeseed straw. The copper content of straw was comparable in spring and winter rapeseed. Sulfur application to soil increased the concentrations of zinc and manganese in winter rapeseed straw, and it had no significant effect on the levels of those minerals in spring rapeseed straw. Spring rapeseed cake had a significantly higher content of copper and zinc, compared with winter rapeseed cake. Manganese concentrations in the cake of spring and winter rapeseed were similar. Sulfur fertilization contributed to a significant increase in the concentrations of zinc and manganese in winter rapeseed cake. The manganese content of spring rapeseed cake decreased significantly in response to sulfur fertilization, which had no effect on the concentrations of the other micronutrients.

19.2.2014