The paper presents the results from years 1998-2001, which aim was to describe the influence of stubble catch crops which were plowed down in autumn and left in the form of mulch till spring, in combinations with or without straw on the yield and the structure of yield of potato tubers. A field experiments were carried out at the Experimental Farm in Zawady, owned by the University of Podlasie in Siedlce. Two factors were taken into account: I - stubble catch crop fertilization (control object - without intercrop fertilization, farmyard manure, white mustard, phacelia, white mustard-mulch, phacelia-mulch); II - straw fertilization (without straw, with straw). The yield of spring barley straw was determined, the yield of fresh mass of stubble catch crop and its content of dry mass and macroelements (N, P, K, Ca and Mg). In the first year after organic fertilization the potatoes were cultivated. During the harvest the total and commercial yield, and also after harvest the structure of tuber yield was determined. The results pointed that, the highest yield of potato tubers was achieved from combinations fertilized with phacelia which was plowed down in autumn, and also phacelia left in the form of mulch till spring in combination with straw. Stubble catch crop and farmyard manure fertilization caused the increase of participation of medium and large tubers in yield.
