The research was conducted during the years 2000-2006 on the base of a long-term study established in 1957, at the Experimental Station Brody (52^o26’ N; 16^o18’ E) belonging to the University of Life Sciences in Poznań. Potato was grown continuously and in seven-course crop rotation at four levels of fertilization: control without fertilization, farmyard manure, farmyard manure + NPK, NPK. In continuous cropping the mean yield of potato was lowered by 50.8% as compared with crop rotation for 7-year period. The highest yield of potato tubers was obtained after combined treatment with farmyard manure and NPK. Fertilization only with farmyard manure or NPK decreased the tuber yield by 14.6 and 22.8 per cent, respectively. Combined farmyard manure and NPK treatment had a favourite effect on N, P, K and Mg content in tubers compared to NPK plots, but decreased dry matter, Ca and starch contents.

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