Alterations in the Nitrogen Metabolism Ofmedicago Sativaanddactylis Glomerataas Influenced by Potassium and Sulfur Nutrition

The cold–water–soluble nitrogen of alfalfa and orchardgrass was fractionated into ammonia, amide, nitrate, and amino nitrogen. Normal, potassium-deficient, sulfur-deficient, and potassium- plus sulfur-deficient forage samples were used. Determinations were also made of the water-soluble amino acids and of the insoluble nitrogen.Potassium deficiency resulted in an increase in ammonia nitrogen. Sulfur deficiency resulted in an increase in nitrate and amide nitrogen.Of the 18 amino acids determined in both species, arginine, glutamic acid, and aspartic acid were increased by sulfur deficiency but potassium deficiency had no effect on these acids. Leucine and lysine increased in potassium-deficient plants but were not affected by sulfur deficiency. Alanine was decreased by potassium deficiency. Glycine, valine, isoleucine, tyrosine, phenylalanine, tryptophan, histidine, and ornithine increased under conditions of potassium or sulfur deficiency.