The experiment was set up at the University of Debrecen's Látókép Crop Production Experiment Site, where calcareous chernozem soil with excellent properties is available (Nagy 2019). The measurements were carried out in a multifactorial long-term fertilization experiment to investigate the hybrid-specific nutrient levels of control, 120 kg ha-1 N+PK and 300 kg ha-1 N+PK (Nagy 2019). Phosphorus and potassium were the same in each plot, applied as autumn basal fertilizer (P2O5 184 kg ha-1, K2O 216 kg ha-1). In the experiment, six different maize genotypes, classified in different maturity groups, were tested. The yields measured in the experiment varied between 9.39 and 10.88 t ha-1. The highest value was measured for the H2 hybrid, which also excelled in protein and moisture content. SPAD values measured at four-leaf stage were positively correlated with yield in several genotypes, while a positive correlation was also measured with protein content in hybrid H1 and oil content in hybrid H3. Based on our measurements, there were significant differences between genotypes at the four main phenological stages studied. We measured the highest values for the H1 at V4, H2 at V8, H6 at V12 and H4 at R3 (38.36, 51.92, 44.45 and 44.31). Our study shows that different nitrogen supply has a significant positive effect on yield and protein content. The effect on yield and content parameters varies between each genotype. Relative chlorophyll content values were well correlated with yield also in the early vegetative stage, and in the generative stage showed a strong positive correlation in all cases. Based on our research results, relative chlorophyll content serves as a proper measure of yield.

Keywords: maize, long-term field experiment, nutrient response, nitrogen fertilisation