The interactions between N×Cu were examined in winter barley in a field experiment on calcareous chernozem loamy soil in 1990. The ploughed layer of the soil of the production site contained 3% humus, around 5% CaCO3 and around 20% clay. According to the performed soil analyses, the area was rich in Ca, Mg, K, Mn, while it had a satisfactory supply of Cu, medium supply of N and weak-medium supply of P and Zn. The groundwater level is 13–15 m and the area is drought-sensitive. The experiment was established with 4 N×3 Cu=12 treatments×3 replications=36 plots. N was applied in 0, 100, 200 and 300 kg ha-1 doses in the form of Ca ammonium nitrate, while Cu was applied in 0, 50 and 100 kg ha-1 doses in the form of CuSO4. Main results:

The grain yield of winter barley was significantly increased by 100 kg ha-1 year-1 N application by 39% (1.4 t ha-1). However, larger N doses, such as 200 and 300 kg ha-1 year-1 caused N over fertilisation and resulted in 0.2–0.4 t ha-1 decrease of grain yield. Cu fertilisation did not affect yield. The N load increased the N concentration of the vegetable organs and that of the examined cations. The N supply enhanced the Cu uptake of the above-ground organs more significantly than Cu fertilisation. However, the Cu content of the root increased 2–3 times as a result of applying N and Cu. As a consequence of the positive interaction between N×Cu, the measured amount of Cu in the control treatment (5 mg kg-1) increased 6 times to 29 mg kg-1. At the same time, the Cu which accumulated in the root was transported to above-ground organs only slightly or it was not transported at all. The vertical movement of Cu was blocked.

Keywords: N×Cu interactions, field trial, winter barley, calcareous chernozem soil