The paper presents results of the investigations conducted in the years 2001-2004, which aimed to assess the influence of undersown crops and stubble catch crops on yielding of potatoes cultivated under changing weather conditions. The following combinations of intercrop fertilization were applied: control object (without intercrop fertilization), farmyard manure, undersown crop (black medic, black medic+Italian ryegrass), stubble catch crop (phacelia, phacelia - mulch). In autumn, the content of dry mass and macroelements (N, P, K, Ca and Mg) in potato plants and in farmyard manure was determined. In the first year after intercrop fertilization table potatoes were cultivated. During harvest a total yield and commercial yield of potato tubers were assessed, and after harvest the content of starch was determined. The results obtained showed that weather conditions in the period of investigations significantly modified the yields of potato tubers. The undersown crops applied (black medic+Italian ryegrass and black medic) and stubble catch crops (phacelia both plowed down in the autumn or left in the form of mulch till the spring, time alike) completely substituted for the farmyard manure in potato fertilization.
