In a long-term field trial on chernozem soil in the Hajdúság region, the following two aspects were analysed: 1) the effect of different fertilisation levels at a specific crop density level (60 thousand ha-1) and 2) the effect of different crop density levels at a specific fertilisation level (N120P90K90) on the following parameters: plant height, corn smut infection, fusarium infection, lodging, Push-test and crop yield.

Data of the year 2010 were analysed. Three crop rotation models were used [mono- and biculture (wheat, maize), triculture (pea, wheat, maize)]. Five fertilisation levels [control (untreated), N60P45K45, N120P90K90, N180P135K135, N240P180K180] and three crop density levels were used (40 thousand ha-1, 60 thousand ha-1, 80 thousand ha-1).

The increasing fertiliser doses significantly increased plant height up to the level of N240+PK; at N240P180K180 crop density the plant height ranged between 247.0 and 286.4 cm respectively of the crop rotation system. Fertilisation levels influenced corn smut infection, fusarium ear rot, lodging and Push-test values. The highest values were obtained with N240+PK fertilisation level in all three crop rotation systems. The crop rotation system influenced the optimal level of fertilisation. The highest yield was obtained with N240+PK (8726 kg ha-1), N180+PK (9371 kg ha-1) and N120+PK (9424 kg ha-1) fertilisation levels in monoculture, biculture and triculture, respectively.

The higher crop densities caused no significant change in the agronomic and plant health parameters at the fertilisation level (N120P90K90) in the three crop rotation systems. At higher crop density levels, yields also increased. The highest yields were obtained at the 80 thousand ha-1 crop density level (in monoculture: 7937 kg ha-1, in biculture: 9290 kg ha-1, in triculture: 9510 kg ha-1). Crop yields significantly increased up to 60 thousand ha-1 crop density level; however, no significant increase was observed at the 80 thousand ha-1 crop density level.

There was no correlation between crop density and agronomic features in either crop rotation model. On the contrary, in all three crop rotation models there was strong or medium correlation between fertilisation and plant height (0.928–0.967), rust infection (0.734–0.795), fusarium ear rot (0.658–0.817), and lodging (0.752–0.825), as well as Push test values (0.728–0.867) and crop yield (0.545–0.898).

Keywords: corn, crop rotation, fertilisation, yield, agronomic traits