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Agronomy Journal Abstract -

Changes in the Concentration of Nitrogenous Fractions in Alfalfa Herbage with Advance in Maturity1


This article in AJ

  1. Vol. 64 No. 3, p. 326-327
    Received: Aug 12, 1971

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  1. Chin-tian Lee and
  2. Dale Smith2



Little information is available in which changes in the concentrations of total, protein, nonprotein, ammonium, nitrate:, free α-amino, asparagine, and glutamine N in alfalfa (Medicago sativa L.) herbage have been measured at successive growth stages in the same investigation. In the current study, concentrations (% dry weight) of these N fractions were analyzed for the leaflets, stems, and total herbage of ‘Vernal’ alfalfa sampled when the spring growth in 1966 was 25-, 41-, and 53-cm tall, and at first, 25%, and 75% flower.

All N fractions decreased in percentage in the leaflets, stems, and total herbage with advance in maturity. Percentages of total N, protein N, and non-protein N were higher in the leaflets than stems at all stages of growth, while percentages of ammonium N and glutamine N were similar in leaflets and stems. In contrast, percentages of nitrate N, free a-amino N, and asparagine N were higher in the stems than leaflets. Percentage decreases in the concentration of N f.ractions in the total herbage from the youngest (25-cm tall) to the oldest (75% flower) stage ranged from a low of 50% for protein N to a high of 75% for nitrate N.

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