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This article in CS

  1. Vol. 17 No. 1, p. 169-172
    Received: Mar 4, 1976

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Nodulation of Soybeans Grown Hydroponically on Urea1

  1. J. T. Vigue,
  2. J. E. Harper,
  3. R. H. Hageman and
  4. D. B. Peters2



Soybeans [Glycine max (L.) Merr.] were grown hydroponically to determine the effects of urea- and nitrate-N sources on nodulation. Urea allowed effective nodule development and function, as evidenced by nodule mass, acetylene reduction, and difference between the total Kjeldahl N gain per plant and urea uptake measurements. Plants grown in solutions with as high as 18 mM urea-N produced nodules capable of N2 fixation (C2H2 reduction assay) while NO3 concentrations low as 2 mM inhibited nodulation. The amount of N fixed by nodules of plants grown on urea varied from 27 to 71% of total plant N, depending on urea concentrations of the nutrient solutions.

Urea uptake by the plants was slower than NO3 uptake, regardless of urea concentration supplied. Therefore, internal concentrations of N or N-components in the plant were likely lower with urea than with NO3 nutrition which may have partially accounted for the degree and effectiveness of nodulation. Growth on urea is a convenient hydroponic method of producing healthy, vigorous, nodulated soybeans that are capable of N2 fixation.

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