The purpose of this study was to determine the effect of the soil conditioner UGmax on nitrogen, phosphorus and magnesium contents in potato tubers. A field experiment was carried out at the Zawady Experimental Farm in 2008-2010. The trial was set up as a split-plot design with three replications; the soil was classified as the very good rye complex of soil quality. The following factors were examined: factor I: table potato cultivars (Satina and Tajfun), and factor II: timing and method of UGmax application: 1 – control – no UGmax, 2 – 1.0 dm³·ha^-1 – applied once before planting of potato tubers, 3 – 1.0 dm³·ha^-1 – split application: ½pre-plant and ½ foliar application, 2.0 dm³·ha^-1 – split application: ½ pre-plant and ½ foliar application, 4 – 1.0 dm³·ha^-1 – split foliar applications at two dates. UGmax significantly increased nitrogen content in potato tubers compared with the control. Split application of UGmax at the rate of 2.0 dm³·ha^-1 (pre-plant spraying followed by two foliar applications) was the best method of application. Moreover, the weather conditions in the study years and potato cultivars had a significant effect on nitrogen content in tubers. Satina accumulated more nitrogen than Tajfun. By contrast, neither UGmax application, cultivars nor weather conditions influenced phosphorus or magnesium contents in potato tubers.

93-101