THE INFLUENCE OF SOIL REACTION ON THE EFFECTS OF MOLYBDENUM FOLIAR FERTILIZATION OF OILSEED RAPE

Thirty-three field trials have been carried out on soils of different acidity (pH=4.1-7.1) to investigate the effect of foliar fertilization with molybdenum on oilseed rape. Three rates of the element: 30, 60 and 120 g Mo.ha(-1), were applied on two dates: in the spring, a few days after the growing season started, and during the early stem formation stage. In the group of trials on very acidic and acidic soils, seed yields were on average 0.08 t.ha(-1) higher. The regression equation demonstrated that a relative seed yield increase obtained as a result of molybdenum fertilization depended on the concentration of manganese and percentage of the silt fraction in the soil. Oilseed rape grown on slightly acidic and neutral soils responded to molybdenum fertilization with an average seed yield increase of 0.02t.ha(-1). The rate of molybdenum had a significant effect on rape yields only in the group of trials set up on slightly acidic and neutral soils. No significant difference was found between 60 and 120 g Mo.ha(-1). However, both of these rates were more effective than the lowest dose of 30 g Mo.ha(-1). No evidence was found to support any relationship between the date of molybdenum application and seed yields or any interaction between Mo rates and application dates in either group of the trials.