The purpose of our experimental work focusing on the development of the fertilisation consultancy system of winter barley was to examine the effect of N, P and K supply on the yield, protein content, amino-acid composition and mineral element content of winter barley on well distinguished nutrient supply levels in a long-term fertilisation experiment, as well as to determine N, P and K supply limit values related to chernozem meadow soil. The long-term fertilisation experiment was established in 1989 on deeply calcareous chernozem meadow soil on 4–4 N, P and K supply levels, using a whole treatment combination with 64 treatments and split-split-plot design. In the winter barley experiments, the number of N fertilisation treatments were increased to seven, using plot halving. This study presents the yield and protein content results of experiments performed between 2006–2008, based on which the following conclusions can be drawn:

1. 160 kg ha-1 split N fertilisation resulted in the highest yield of winter barley in a year with average precipitation on chernozem meadow soil with 2.8–3.2% humus content and good N supply ability. In a year with deficient water supply, when N conversation ratio is more limited, 80 kg ha-1 split N fertilisation was shown to be the most successful. Following a dry year, when a significant amount (80–100 kg ha-1) mineral N remained in the soil following the previous crop and water supply was more favourable than average, the 80 kg ha-1 split N fertilisation provided nearly 6 t ha-1 yield. Crop year without N fertilisation resulted in 1.7 t ha-1 yield difference, while the same value was 2 t ha-1 on the level of maximum yields.

2. Averaged over the three examined years, no significant difference could be observed in the yield of winter barley in the 118–282 mg kg-1 AL-P2O5 supply range and 95% of the maximum yield could be achieved without P fertilisation. Moderate P effect can be expected on chernozem meadow soil in the 160–220 mg kg-1 AL-P2O5 supply range in certain years.

3. No K effects could be shown in the 199–377 mg kg-1 AL-K2O supply range of the soil and 99% of the maximum yield could be achieved without K fertilisation, averaged over the three examined years. On chernozem meadow soil, 200–235 mg kg-1 AL-K2O supply can be considered favourable for winter barley.

4. The K×N interaction shows that significant grain yield reduction can be observed on the 80, 160, 240 kg ha-1 N fertilisation levels above the 300 mg kg-1 AL-K2O supply level of the soil in the majority of cases. The yield increasing effect of N fertilisation was more pronounced without K fertilisation.

5. No notable change was observed in the raw protein content of the grain yield of winter barley in the 118–282 mg kg-1 AL-P2O5 supply range and the 199–377 mg kg-1 AL-K2O supply range of the soil. Averaged over the three examined years, the raw protein content significantly increased until 160 kg ha-1 N.

Keywords: N, P and K supply, winter barley, yield, raw protein content