Effect of applying increasing levels of nitrogen to ryegrass: I.—Composition of various nitrogenous fractions and free amino acids

Heavy application of fertiliser N caused a rise in the non‐protein N content of the plant which was accompanied by a sharp rise in the free amino acid N, other organic nitrogenous constituents and nitrate N. The peptide N fraction of the plant was high when no nitrogen was applied, decreased with moderate supply of N and rose again slightly when heavy doses of N were applied. There was a steady increase in true‐protein content with increase of N application; without N, accumulation of asparagine was noted. With a limited supply of N the dicarboxylic amino acids increased and also there was a considerable reduction of asparagine. Heavy fertilisation with N increased considerably the contents of asparagine and glutamine, the increase of glutamine being greater than that of asparagine, and was also accompanied by an increased content of all the amino acids.