Nitrogen replenishment is one of the main factors of increasing maize yield, in addition to applying the adequate quantity and reducing unwanted environmental impacts. During the research, we wanted to know how the amount of applied nitrogen and its time of application affect maize productivity and earnings under different environmental conditions.

We performed our analyses at the Látókép Crop Production Experiment Plant of the University of Debrecen in a small-plot long-term experiment with split-strip-plot design and two replications on calcareous chernozem soil with deep humus layers formed on loess. The experiment was carried out in a wet crop year (2016) and a crop year with average precipitation, under natural precipitation supply. The examined hybrids were Armagnac (FAO 490) and Renfor (FAO 320).

In the long-term field experiment, the N fertiliser doses were applied as basal and top dressing in addition to the non-fertilised control treatment. The 60 and 120 kg N ha-1 doses were applied as spring basal dressing, which were followed by two occasions of top dressing at the V6 and V12 phenophases, applying 30 kg N ha-1 on each occasion.

The amount of precipitation in 2016 was higher than the 30-year average and it was better utilised by Armagnac, the hybrid which has a longer ripening period (FAO 490), while both the basal and the top dressing was also better utilised by this hybrid than Renfor, the hybrid with a shorter ripening period (FAO 320), averaged over the different treatments. The yield of Armagnac was 21.7% higher, while that of Renfor was 10.4% higher in the wet crop year.

In the case of both hybrids, more effective uptake and better conversion ratio were obtained in the 60 kg N ha-1 basal dressing + the V6 development stage by applying +30 kg N ha-1 (V690) in the wet crop year (2016). In the crop year with average precipitation (2017), there was a difference between the success of top dressing between the examined hybrids. In the case of the Armagnac (FAO 490) hybrid, no significant yield surplus resulted from top dressing and the 120 kg N ha-1 basal dressing was shown to be successful. The early top dressing (V6150) applied on the basal dose of 120 kg N ha-1 was more favourable in the case of the Renfor (FAO 320) hybrid.

The yield advantage of the Armagnac (FAO 490) hybrid compared to the Renfor (FAO 320) hybrid was significant in the wet crop year of 2016, with the exception of two treatments (A60 and V12180). The greatest yield advantage was reached with the V12120 (6.750 t ha-1 P<0.001) treatment. In the average crop year (2017), significant difference could be shown between the two hybrids in three treatments (A120, V12120 and V12180 kg N ha-1). Armagnac (FAO 490) showed the most significant yield advantage in the A120 (2.529 t ha-1 P<0.05) treatment.

The most favourable earning of nutrient management (N) was provided by the spring basal dressing of 120 kg N ha-1 and the +30 kg N ha-1 top dressing applied at the early V6 phenophase (V6150), averaged over the different hybrids and crop years. Independently of the prevailing environmental conditions, the Renfor (FAO 320) hybrid showed the highest profitability as a result of the V6150 treatment, while the same outcome of Armagnac (FAO 490) was achieved as a result of the top dressing applied at the V12 phenophase, which could be provided with the lower dose of V12120 in the wet crop year (2016) and the higher dose of V12180 in the average crop year (2017).

Altogether, based on the analysis of yield and marginal income, it can be concluded that the recommended technology consists of a spring basal dressing of 120 kg N ha-1 and a top dressing dose of 30 kg N ha-1 applied at the early V6 phenophase. The obtained findings also verify that the effect of N is greatly affected by crop year, genotype and various technological elements. In addition, efficiency must be determined for each hybrid with the consideration of the given crop year.

Keywords: maize, basal and top dressing, extra income