Field studies were conducted in Poland, from 2001 to 2004, to evaluate the influence of undersown crop plowed down in autumn and of stubble crop plowed down in autumn and left in the form of mulch until spring in combinations with or without straw on potato tuber yield and its structure. The effects of 2 factors were assessed, i.e. intercrop fertilizer application, control object, farmyard manure and undersown crop biomass which was plowed down in autumn (white clover + Italian ryegrass), stubble crop-biomass plowed down in autumn (white mustard) and stubble crop-biomass left in the form of mulch until spring (white mustard) and straw fertilizer application, a sub-block with straw and a sub-block without straw. During harvest time, the total yield and commercial yield were assessed. The yield structure was determined after harvest. The highest yield of potato tubers was obtained from the object that had been fertilized with a mixture of white clover with Italian ryegrass. Fertilizer application with intercrops and farmyard manure had favourable influence on the shaping of tuber yield structure. The yield produced in sub-blocks with straw, compared to that produced in sub-blocks with no straw, was characterized by a lower share of medium-sized tubers and higher share of small tubers.
