The soil water balance of a soil population was examined in a 27-year-long polyfactoral long-term experiment in the wet year of 2017. It was concluded from the examination results that the moisture content of the 200 cm deep soil profile was greatly affected by the high amount of precipitation of the winter period. Soybean uses the moisture content of the 100–140 cm deep soil profile intensively, while the lower layer of 140–200 cm depth has a lower significance in the water supply of the crop stand.

The leaf area of the soy population was also measured. LAI readings properly show the favourable effect of irrigation and the larger assimilation surface was also shown in the quantity of yield in the second half of the growing season of soybean in the irrigated treatments. However, the effect of the applied nutrient treatments were not significant.

Based on the analysis of yield, it was concluded that the yield obtained in the case of the medium nutrient supply level was not the highest on non-irrigated plots, while the highest average yield (5060 kg ha-1) was harvested on non-fertilised plots. This difference was not significant. In addition, no significant effects were observed between the nutrient treatments within each irrigation treatment.

The continuation of the experiment is substantiated in crop years different from the examined year; therefore, the experiment is going to be performed also in 2018.

Keywords: soil moisture, irrigation, nutrient, precipitation, soybean, yield