In order to develop a maize fertilisation consultancy system based on soil and plant analysis, we examined the effect of N fertilisation (0, 80, 160, 240 kg N ha-1) on the maize grain yield, nutrient concentration and the interactions between nutrients during a 8-year-long experimental period. The long-term fertilisation experiment was established in 1989 on chernozem meadow soil with a deep calcareous layer. The experiment had four N, P and K levels of supply, the entire treatment combination was performed in a split-split-plot design, using 64 treatments. This study outlines the N fertilisation results of the experiments performed between 2001–2008 (in the 12th–19th years of the long-term experiment). The following conclusions can be drawn:

1. Averaged over the 8 years, the pre-sowing NO3-N content of the 0–60 cm layer on the non-fertilised chernozem meadow soil with 2.8–3.2% humus content was 48 kg ha-1 and grain yield was 6.24 t ha-1. N fertilisation with doses higher than 80 kg ha-1 resulted in further significant yield surplus only in 3 of the 8 examined years. Grain yield significantly increased until the the pre-sowing 80–100 kg ha-1 NO3-N level of the 0–60 cm layer of the soil. The 240 kg ha-1 N decreased grain yield in comparison with the maximum yield.

2. Depending on the level of N fertilisation, the pre-sowing NO3-N content of the 0–60 cm layer of the soil varied between 30–205 kg ha-1 over the experimental period. The N concentration of maize leaves showed a close correlation (r=0.76) with the soil NO3-N level at the beginning of tasseling.

3. Based on the interaction between the N concentration of maize leaves measured at the beginning of tasseling and grain yield, the satisfactory limit value of N supply was 2.0–3.2% between 2002–2008 at 95% of the maximum grain yield, while it was 3.5–4.8% in 2001. The evaluation of the databases of the eight experimental years showed that in order to reach 10–14 t ha-1 yield, the satisfactory limit value of N concentration has to be between 2.0–4.0% at the beginning of tasseling.

4. On the soil with 120–360 mg kg-1 AL-P2O5 supply, N fertilisation increased the P concentration of leaves in two years and also decreased in other two years. During these years, interaction was shown between the N and P concentrations of leaves. The P content of leaves was between 0.22–0.35% at the beginning of tasseling, depending on the level of N fertilisation and the crop year.

5. On the soil with 200–465 mg kg-1 AL-K2O supply, N fertilisation did not significantly affect the K concentration of leaves. The Ca content was between 0.27–0.54% over the experimental period. The Mg content of leaves was between 0.18–0.38% and the Mg concentration increasing effect of N fertilisation was observed in the two years which showed the highest yields.

6. The Mn concentration of leaves showed positive interactions every year with an increasing level of N nutrition. The N fertilisation decreased the Zn concentration of leaves only in especially dry years. In certain years, there was a positive correlation between the N an Zn concentration of leaves. The more favourable level of N supply significantly increased the leaf Cu content in 3 years and its Fe content in 2 years.

Keywords: maize, N fertilisation, nutrient concentration, nutrient interaction