The yield and chemical composition of potato tubers is significantly diversified by fertilization with undersown crops and by the production system. The study presents research results from the years 2007-2010 whose aim is comparison of the yield and quality of potato tubers fertilized with undersown crops in an integrated and organic production system. Two factors were studied in the experiment: I – fertilization with an undersown crop: control (without fertilization with an undersown crop), manure, undersown crop – the biomassis ploughed in autumn (serradella, annual ryegrass), undersown crop – biomass left until spring in the form of mulch (serradella, annual ryegrass), II – production system: integrated and organic. Undersown crops were incorporated into spring triticale cultivated for grain. In the first year after applying undersown crops, edible potatoes were cultivated. While harvesting potato tubers, total and marketable yields were determined. In the collected tuber samples, the content of the following was determined: starch, vitamin C and true protein. Significantly, the highest yields of potato tubers were obtained from the plot fertilized with serradella in the form of mulch. Higher yields of potato tubers were obtained in an integrated than in an organic production system. Vitamin C content in potato tubers was significantly diversified by fertilization with an undersown crop, by the production system and their interaction. Significantly, the highest content of true protein was observed in potato tubers fertilized with serradella both ploughed in autumn, and left until spring in the form of mulch. Production system diversified the yield and chemical composition of potato tubers. The highest starch content was characteristic of potato tubers fertilized with annual ryegrass left until spring in the form of mulch, the highest vitamin C content was found in potato tubers fertilized with undersown crops left until spring in the form of mulch, and the highest true protein content in potato tubers fertilized with serradella both ploughed in autumn and left until spring in the form of mulch. Fertilization with serradella, both ploughed in autumn and left until spring in the form of mulch, fully substitutes manure in an integrated production system of potato.

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