The results of the field experiments provide a stable orientation basis for the continuous, broad development of agriculture. The long-term complex fertilisation experiment established in 1983 at the University of Debrecen's Látókép Experiment Site provides a unique opportunity to compare the nutrient responses of maize genotypes between non-fertilised control plots and five increasing nitrogen application rates in both irrigated and non-irrigated experimental conditions. Based on many years of experimental results, we found statistically proven yield enhancing effects of all nitrogen fertilisation levels. Nitrogen utilisation efficiency was highest at the 60 kg/ha treatment, resulting in 45.8% higher yields. Evaluating the irrigated experimental version, we found that optimal water supply resulted in an increase in yield stability for both the control and increasing nitrogen doses, with less measurable seasonal variability in yield, with a yield increase of 0.49–2.58 t/ha. The effect of irrigation in increasing crop stability was also reflected in fertiliser use efficiency. On average, 120 kg nitrogen/ha increased maize yield by 62–105% and 180 kg nitrogen/ha by 57–112% compared to control plots.