Interactions between N × Cu in a winter wheat field experiment established on calcareous chernozem were examined in 1989. The soil of the production site contained 3% humus, 5% CaCO3 and 20% clay in the ploughed layer. Based on soil analyses, the area Ca, Mg, K and Mn level of the area is high, the Cu content is satisfactory, the N level is average and the P and Zn level was weak-average. Groundwater level is at 13–15 m and the area is drought sensitive. The experiment was established with 4N × 3Cu = 12 treatments × 3 replications = 36 plots. 0, 100, 200 and 300 kg ha-1 N and Cu 0, 50 and 100 kg ha-1 Cu were applied in the forms of Ca ammonium nitrate and CuSO4, respectively. There was drought in April, May and July.

Main results:

- The weight of air-dry shoot measured at the end of tillering and the weight of straw measured at harvesting increased by 24% as a result of N fertilisation in comparison with the N control treatment. There was no significant surplus in grain yield. Yield was not affected by Cu fertilisation. Altogether, 12.4 t ha-1 air-dry biomass was formed, of which the proportion of primary and secondary yield was 50–50%. Nearly two thirds of biomass was accumulated during the 50 days of the generative phase (from the beginning of anthesis until harvesting). The grain yield of wheat was not significantly increased either by N or by Cu on this soil which has average N and satisfactory Cu content. The reason for the lacking N effects were the supplementary N supply in the second year after ploughing the alfalfa root mass back into the soil.

- In general, the N, K, Ca, Mg and Na content of the plant organs increased with the increasing N supply; therefore, N abundance facilitated the incorporation of the main cations. As a result of N × Cu treatments, the concentration of Cu increased by 50–100% in the shoot and root of young plants. On average, the root was twice as rich in Cu as the shoot. The root was the accumulation organ of other microelements and Mg.

- Based on the composition of shoot measured at the end of tillering, it can be concluded that the crop stand had a satisfactory supply of N, P, K, Mn and Cu. Compared to the optimal supply levels in technical literature, the Ca and Mg levels increased in this calcareous soil, while Zn had a low concentration.

- The specific element content of maize (1t grain + its secondary yield is equal to 24 kg N, 14–15 kg K2O, 9 kg P2O5, 4 kg CaO and 3–4 kg MgO. Our data can be used in determining the element need of the planned yield during consultancy.

- The NO3-N stock of the 0-60 cm soil layer in the spring of 1989 reflected the N treatments with 42, 84, 135 and 180 kg ha-1 NO3-N content. On average, around 45% of the applied amount of N could be detected in the examined 0-60 cm soil layer. The loss leached into the deeper layers or as a result of denitrification is unknown.

Keywords: N×Cu interactions, field trial, wheat, mineral elements uptake