Effect of fertilization on the Mo content in potato tubers (Solanum tuberosum L.) and sunflower biomass (Helianthus annuus L.) cultivated on a Luvisol formed from loess

Plant demand for molybdenum is small, but it is a micronutrient of great significance for the proper development and functioning of organisms. Its deficiencies may disturb the absorption and influence of other elements on living organisms. The availability of molybdenum for plants depends on many factors, including the fertilization used. The aim of the study was to determine the effect of liming and differentiated NPK mineral fertilization against the background of a constant level of Mg fertilization on the molybdenum content in potato tubers and in the green mass of fodder sunflower grown on loess soil in four and three rotations, respectively. The research was carried out as a long-term experiment on a field owned by the University of Rzeszow in Krasne near Rzeszow (Rzeszow Foothills). The soil on which the research was carried out was a Haplic Luvisols formed from loess. The experiment was set up in a random sub-block design with four replicates. The first variable factor was liming (A2) or its lack (A1), while the second one consisted of different doses of mineral fertilization (14 fertilizer objects) with constant magnesium nutrition. Triple superphosphate contained significant amounts of molybdenum: from traces to 18 mg Mo kg-1. Plant samples were collected after potato and sunflower harvest from four rotations. Molybdenum in dry plant material was determined colorimetrically with the thiocyanate method. The molybdenum content in potato tubers ranged from 0.147 to 0.573 mg kg-1, being much higher in the green mass of fodder sunflower, where it ranged from 0.467 to 2.280 mg kg-1. Liming increased the molybdenum content in the green mass of fodder sunflower. This treatment caused significant changes in the content of this lement in potato tubers. The mineral fertilization of NPK (regardless of liming) increased the molybdenum content in the green mass of fodder sunflower and in potato tubers compared to the object without mineral fertilization.