In 2-year field studies on light soil the effect of the microbiological preparation Blue N applied foliarly on the yield and content of selected components in potato tubers was determined. The microbiological preparation used in the research at a dose of 333 g ha-1 contained Methylobacterium symbioticum bacteria with properties of nitrogen fixation from the air. The experimental factors were: varieties (Hermes, Tajfun), objects (control object - without the use of microbiological preparation, object with the use of the Blue N preparation), doses of mineral nitrogen (basic dose - 100 kg ha-1, dose reduced by 30% - 70 kg ha-1. The studies assessed the level of total tuber yield and the content in tubers of dry matter, starch, vitamin C, nitrates, total nitrogen and the uptake of this component with the tuber yield. The highest increase in tuber yield in the object with the microbiological preparation was recorded after the application of a nitrogen dose of 70 kg ha-1 in relation to the Tajfun variety. On average, in the studies on the object after the application of the microbiological preparation, the tuber yield was higher by 6.1% compared to the control object, without its use. The microbiological preparation significantly reduced the level of nitrates, increased the content of dry matter and total nitrogen in tubers and the uptake of this component with the yield compared to the control object. Based on the yield of tubers, it was shown that the use of microbiological preparation Blue N enabled a reduction of the dose of mineral nitrogen by about 30 kg ha-1.