In a long term experiment (established in 1983), we investigated the grain yield parameters of maize in the year 2023 with favourable water supply on chernozem soil with calcareous loess. The tests were carried out with the DA 7250 NIR instrument. Crop rotation did not significantly affect protein, oil and starch content. The effect of irrigation varied depending on the rotation. In mono- and tri-cultures, irrigation decreased protein content (mono: dry 7.20%, irrigated 6.90%; tri: dry 7.44%, irrigated 7.24%), while starch content increased (mono: dry 64.97%, irrigated 65.22%; tri: dry 64.78%, irrigated 65.06%). Opposite effects were observed in bicultural conditions (protein - dry: 6.88%, irrigated: 7.21%; starch - dry: 65.16%, irrigated 64.18%). Among the agrotechnical elements, fertilisation had the highest significant effect on protein and starch content of maize. In all three crop rotations, increasing fertiliser rates increased the protein content (mean of dry and irrigated treatments from 6.51% to 7.39% in monoculture, from 6.56% to 7.35% in biculture, from 6.97% to 7.35% in tri-culture), 55%), while, on the contrary, the starch content was reduced (from 65.99% to 64.55% in monoculture, from 65.78% to 63.94% in biculture, from 65.15% to 64.42% in triculture). The oil content was not affected by fertilisation.