The experiment was done in Bałcyny – 10 km to the south from Ostróda, on fawn soil in years 1973-1998. Plants were cultivated in an 8-rotation-cropping system in two first rotations, and after that in a 7-rotation-cropping system without mixture of meadow clover with grasses. Spring barley was cultivated in two fields of rotation-cropping system: after potatoes and after corn collected on green mass. The following objects were considered in the experiments: 0 – control, 1 – liquid manure, single dose (I), 2 – liquid manure, dose I + PK, 3 – liquid manure, double dose (II), 4 – liquid manure, dose II + PK, 5 – manure, 6 – manure + PK, 7 – NPK. The annual doses of fertil-izers applied were as follows: liquid manure single dose (I) – 34.9 t, liquid manure double dose (II) – 69.6 t, manure – 21.5 t ha-1 and NPK – 256 kg ha-1. Liquid manure in single dose (I), manure and NPK were balanced by the quantity of introduced nitrogen, and liquid manure in double dose (II) corresponded to manure balanced by the quantity of organic carbon. PK fertilization in relation to natural fertilizers was equal to single dose applied in object NPK. The highest yield of spring barley – 5.48 t ha-1 – was obtained by application of manure and mineral fertilization, the lowest – 3.40 t ha-1 – without fertilization. Moreover, in the crop-change year (1981) a decrease of yield, by about 30%, was observed in all cases of exceeded rates of precipitation – in April by about 92%, June – 42%, and July – 74%. The analysis of multiple regression with choice of optimum subset of inde-pendent variables (air temperature, precipitations) showed that precipitations caused only a small significant influence during months IV-VII on the yield of spring barley.