Influence of irrigation and nitrogen fertilization on the amino acid composition of spring wheat

Abstract

Sprinkler irrigation on clay soils in southern Finland decreased the protein content of spring wheat flour in five field experiments in the years 1967—70, by 16 ± 4 per cent on an average. The amino acid composition, however, was improved, because the proportion of lysine was increased by 6 ± 4 %. Accordingly, the content of lysine in flour was decreased by irrigation only by 10 ± 5 %. An increase of fertilizer nitrogen from 68 to 144 kg/ha increased the protein content of wheat flour by 19 ± 5 %, but the proportion of lysine in the amino acid composition decreased by 9 ± 4 %. Therefore, the lysine content in flour was increased by nitrogen fertilization only by 8 ± 5 %. It seemed as if urea and ammonium nitrate limestone would have had about the same effect on the quantity and quality of wheat protein. As a consequence of the reversed influences of irrigation and nitrogen fertilization on the wheat protein it was possible, by means of irrigation and an additional nitrogen fertilization, to produce 65 per cent higher grain yields without any noteworthy changes in the contents of protein or amino acids.