The relationship between relative chlorophyll content (SPAD) and yield was investigated using two maize hybrids of different genotypes (Armagnac; Fornad) in 2020 and 2021. The studies were carried out at the University of Debrecen Látókép Experimental Station in a 1.5 ha double split-plot, two replicate field experiment. In the field experiment, nitrogen (N) fertiliser rates were applied in a split manner as basal and top dressing in the field experiment with no fertiliser application (control). The 60 and 120 kg N ha-1 applied as spring basal fertiliser was followed by two top dressing fertiliser applications at V6 and V12 phenophases at +30 and +30 kg N ha-1. Based on the test results of both years, it can be concluded that SPAD values measured in different phenological phases (V6, V12, Vn, VT, R1 R3 and R6) and in hybrids with different genotypes increased in the vegetative development stage. The highest values were measured at the generative stage. Relative chlorophyll content decreased at the full maturation stage compared to the milk stage (2020: 17%; 2021: 23%). SPAD values and yields increased with higher N doses. The mean SPAD value (40.32±5.56) in the control treatment was 18% lower compared to the V12180 treatment.

The lowest dose of fertiliser (A60) increased the yield of the hybrid Armagnac by 43% and the yield of the hybrid Fornad by 35% on average over the years compared to the control treatment. The 120 kg N ha-1 base treatment caused an additional 49% increase in yield on average compared to the 60 kg N ha-1 basal treatment. A positive correlation between relative chlorophyll content and yield was demonstrated. As the phenophases progressed, different levels of correlation were found between crop years and genotypes. In the Armagnac hybrid, SPAD values measured in both years in the R3 phenophase had the most significant effect on yield development (r=0.84; r=0.80). In the Fornad hybrid, the strongest correlation was observed in the R1 phenophase in 2020 and in the V12 phenophase in 2021 (r=0.87; r=0.79).

Keywords: maize hybrids, nitrogen, SPAD readings, yield