Effects of nitrogen and potassium fertilisers on contents of carbohydrates and free amino acids in Italian ryegrass. II. Changes in the composition of the non‐protein nitrogen fraction and the distribution of individual amino acids

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Abstract
Italian ryegrass (Lolium multiflorum) S22, grown in a greenhouse in K‐deficient soil in pots, was given 40, 80 and 160 mg of N/kg of soil (as ammonium nitrate) and 0, 60, 120 and 240 mg of K/kg of soil (as potassium chloride). In grass grown without added K, increasing N fertiliser increased the concentrations of total N, non‐protein‐N, ammonium‐N, nitrate‐N, free amino acids, amides and amines. With adequate K fertiliser all these N fractions decreased.The percentage distribution of N in the free amino‐acid pool varied with the amount of N and K given. Without K fertiliser, increasing N had no consistent effect on most amino acids and amides, although it decreased the percentages of alanine and ethanolamine. Increasing K had relatively little effect on the percentage distribution in grass given the two smaller amounts of N. However, in the grass given the largest amount of N, it increased the percentage of most amino acids, especially alanine and 4‐amino‐n‐butyric acid, and decreased glutamine and asparagine. β‐Alanine was found only in K‐deficient plants.The effect of K in relation to N metabolism and the nutritive value of herbage is briefly discussed.