The experimental work related to the fertilisation consultancy development of sorghum was to examine the impact of N, P and K supply levels on sorghum yield in a long-term fertilisation experiment well distinguished soil nutrient supply levels, as well as to define the N, P and K supply limit values on chernozem meadow soil. The long-term fertilisation experiment was established in 1989 on deeply calcareous chernozem meadow soil with 4–4 N, P and K supply levels, total treatment combinations and 64 treatments. This study describes the results of the experiments performed between 2000 and 2004 and the following conclusions can be drawn:

1. The highest green yield was observed in the case of 160 kg ha-1 N on chernozem meadow soil with 2.8–3.2% humus content during the four examined years. No overdose (240 kg N ha-1) resulted in decreased green yield in each year. Economical green yield was obtained at the 146 kg ha-1 NO3-N level of the 0–60 layer of the soil before sowing.

2. The green yield of sorghum increased until the 200 mg kg-1 AL-P2O5 supply level of the soil. No significant yield increase was observed above this P supply level, but it rather caused a slight yield decreased in comparison with the highest yield in the majority of the examined years.

3. The 200–250 mg kg-1 AL-K2O supply level of the soil is considered to be a proper level of K supply, as no significant yield increase can be observed at any K level above this point. In the majority of the examined years, green yield decreases in the case of AL-K2O supply levels above 400 mg kg-1.

4. The N×P interactions could be detected in the nutrient supply of sorghum in each year. The yield increasing effect of N fertilisation was more significant in the case of better P supply levels. P fertilisation resulted in higher yield surplus at more favourable N supply levels.

5. P×K interaction could be observed in two out of the five experimental years, when the excessive K supply (453, 465 mg kg-1) caused yield depression in the 195–362 mg kg-1 AL-P2O5 supply range.

Keywords: N, P and K supply, sorghum, yield, long-term experiment