In a long-term mineral fertilisation experiment with 64 treatments representing all possible combinations of four rates each of N, P and K, set up on chernozem meadow soil in Szarvas in 1989. The following N fertiliser rates were applied: 0, 80, 160, 240 kgha -1 year -1 . The protein and oil contents and the amino acid and fatty acid compositions of the maize grain yield were analysed between 1997 and 2004. The protein content of the maize kernels increased by 1.1–1.5 percentage points up to a NO 3 -N level of 80–100 kg ha –1 in the 0–60 cm soil layer prior to sowing. The year had a greater influence on the protein content than the N supplies. In the present experiment it was found that in years with high yields (8,5 tha -1 <) the protein content, averaged over the N treatments, was lower (8.3-10.0 %) than in years with poorer yields (7.5 tha -1 >), when it ranged from 11.2-12.3 %.  No consistent effect of N on the amino acid composition, detectable as a change in the ratio of any amino acid in the majority of experimental years, was observed. The N supplies had no effect on the ratio of isoleucine, theonine, alanine, cysteine, glutamic acid or proline in the protein. Of the seven years investigated, the leucine ratio increased in three years, while that of lysine declined at higher N suppli levels. In two experimental years there was a significant increase in phenylalanine, but a decrease in the glycine ratio as the result of increasing N supplies. Arginine, methionine, valine, aspartic acid, serine acid and tyrosine exhibited significant but inconsistent increases or decreases in two or three years as a function of N supplies. The ratio of essential amino acids exhibited a slight increase in most years up to the 80-100 kgha -1 NO 3 -N supply level. The oil content and fatty acid composition of maize kernels was extremely stable, and was very little affected by the nutrient supplies or the year. During the experimental period excessive N supplies were only found to reduce the oil content and modify the fatty acid composition on one occasion.

maize, protein and oil content, amino and fatty acid composition, N fertiliser response

Presentation: oral