A two-factor pot experiment was carried out in the years 2009-2011 under a permanent plastic-covered tunnel greenhouse at the Mochełek Experimental Station of the University of Technology and Life Sciences in Bydgoszcz (POLAND). The subject of research was the traditional cultivar of yellow lupin, Mister. The design of the experiment included 5 levels of Nmin content in the plant growth medium: from 4.45 mg Nmin.kg-1.d.w.– very low content to 22.5 mg Nmin.kg-1d.w. – very high content. Seeds of yellow lupin were inoculated with agar inoculum containing Bradyrhizobium lupini with or without the addition of genistein. Along with the plant growth, gradual decrease in the mean content of Nmin was observed, especially in the nitrogenous form until the stage of full bloom of lupin plants. No significant effect of the Nmin content was found on the initiation of the nodulation process, number and dry weight of nodules, independently of seed inoculation with Bradyrhizobium lupini and application of genistein. Average or higher content of Nmin in the medium was the reason of the lack of survival in symbiotic bacteria Bradyrhizobium lupini capable of nodulation in the medium after lupin harvest. Only in the case of low and very low Nmin content in the medium, the addition of genistein to bacterial inoculum did affect the increase in the survival of symbiotic bacteria after lupin harvest.
