Statistical analysis showed a significant influence of examined factors and their interaction on the commercial yield of potato tubers (table 3). The highest yields were obtained from objects fertilized white clover, a mixture of white clover and Italian ryegrass and phacelia both plowed in the autumn, and left till spring in the form of mulch. Only on object fertilized with Italian ryegrass and on control object marketable yield of potato tubers was significantly lower than that recorded in farmyard manure. Straw fertilization also significantly differentiate commercial yield of potato tubers. At the sub-block with straw marketable yield of potato tubers was significantly higher than obtained in the sub-block without straw. An interaction has been noted, which shows that indeed the highest marketable yield was obtained from the object fertilized with a mixture of white clover with Italian ryegrass and white clover with straw, and the smallest from the control object without organic fertilization.