Content of macroelements in tubers of several potato varieties depending on the foliar fertilization applied

The aim of the study was to determine the effect of foliar fertilizers containing macro- and microelements, and used in the form of chelates, on the content of macroelements in tubers of several potato varieties. The study was based on a 3-year (2013-2015) field experiment conducted in Haczow (49°39′40″N, 21°53′49″E), on brown, slightly acidic soil. The experiment was established using the method of random subblocks, where the first order factors were foliar fertilization treatments with the following fertilizers: Fortis Duotop Zn Mn + Fortis Aminotop (A), Fortis B Mo + Ferti Agro (B), Fortis Zn Mn + Fortis B Mo (C) and the control object, without foliar fertilization. The second order factors were 4 potato varieties belonging to different classes of earliness (Agnes, Jelly, Viviana, Vineta). Foliar application of all fertilizer combinations contributed to an increase in the magnesium content, while the application of Fortis B Mo + Ferti Agro fertilizers increased the nitrogen and potassium content. Genetic traits differentiated the content of macroelements. Tubers of the cultivar Jelly were characterized by the largest accumulation of phosphorus, potassium, magnesium and calcium, while the Viviana cultivar had the smallest amounts of phosphorus, potassium, calcium. The meteorological conditions in the years of the experiment modified the content of macroelements. Under the dry summer conditions but very wet September in 2013, the tubers accumulated most magnesium and calcium, but contained the least nitrogen, phosphorus and potassium. With excess precipitation in 2014, the tubers were found to contain the most phosphorus, potassium and calcium, while in the dry 2015 year, with a significant shortage of precipitation during the potato growing season and air temperature higher than the long-term average, the tubers accumulated the highest nitrogen but the lowest calcium amounts