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Effects of N, P, and K and their Interactions on the Nitrogen Metabolism of Vegetative Barley Tissue and on the Chemical Composition of Grain in Hydroponic Culture¹

‘Herta’ barley (Hordeum distichon L.) was grown in a greenhouse hydroponics experiment where nitrogen was supplied at concentrations of 10, 50, 100, and 200 ppm N, phosphorus at 25 and 100 ppm P, and potassium at 10, 50, and 200 ppm K in factorial combination. Barley tissue, harvested at the early vegetative, mid-vegetative, and mature stages of development, was analyzed for total N, protein (alcohol-insoluble) N, non-protein (alcohol-soluble) N, nitrate N, and reduced N. All N fractions, except nitrate N in the mature grain increased with increasing concentrations of N in the nutrient solution. As the concentration of P and K was increased, there was an increase in the dry matter yield and a decrease in the percentage of all N fractions, particularly in tissue at the early- and mid-vegetative stages of development. The percent of protein N and non-protein N fractions in the mature grain was lower with 100 P than with 25 P and also lower with 200 K than with 10 K or 50 K. Total production of protein N and non-protein N per plant, however, was greater at the higher rates of P and K largely due to the increased yield of dry matter per plant. Interaction effects of N and K were more significant than NP interactions and than PK interactions except at the early vegetative stage. Potassium appeared to have more effect on the N metabolism of the plant in both vegetative and mature stages than did P.

Key Words: Vegetative stage • Mature stage • Total N • Protein N • Nitrate N

² Head, Soils and Plant Nutrition Section, Charlottetown, and Director, Analytical Chemistry Research Service, respectively.

Received for publication August 12, 1968.