Plant and Soil

, Volume 151, Issue 1, pp 1–9

Phosphorus requirement and sources of nitrogen in three soybean (Glycine max) genotypes, Bragg, nts 382 and Chippewa

  • S. F. B. N. Gunawardena
  • S. K. A. Danso
  • F. Zapata
Research Article

DOI: 10.1007/BF00010780

Cite this article as:
Gunawardena, S.F.B.N., Danso, S.K.A. & Zapata, F. Plant Soil (1993) 151: 1. doi:10.1007/BF00010780


The effect of different levels of soil phosphorus on nodulation, N2 fixation and growth of supernodulating soybean mutant, nts 382, its parent, Bragg, and soybean cultivar, Chippewa, were compared in a greenhouse study. The P rates were, 0, 30, 60 and 90 mg kg−1 soil (P0, P1, P2 and P3, respectively).

The reduced shoot growth of nts 382 (25% at P0 and 17% at P3) could not be attributed to P deficiency, as nts 382 achieved near maximum yield at a lower P rate (P1) than Bragg (P2). The P response of Chippewa that produced the lowest shoot yield, was similar to that of Bragg. Root growth of nts 382 was more retarded than shoot growth (on average 50% that of Bragg), and yet absorbed a similar amount of total P as Bragg. Also, Chippewa that had the lowest root dry matter accumulated the highest P in the shoots. The data indicate that plant growth was influenced by differences in P use efficiency rather than differences in total P.

In contrast to plant growth, nts 382 accumulated 26% more N than Bragg, and Chippewa accumulated a similar amount of N as Bragg. Thus again, Bragg used N most efficiently for growth. Soil N uptake was not governed by root biomass, and Chippewa absorbed more N from soil than both Bragg and nts 382 which absorbed similar amounts of soil N. Nodulation in nts 382 was significantly enhanced, being 528 and 892% greater than Bragg at P0 and P3, respectively, and nts 382 was the only cultivar whose nodulation was consistently enhanced by P addition. The percentage of N derived from fixation (% Ndfa) was not affected by supernodulation, but because of a greater accumulation of total N in nts 382, amount of N fixed (Ndfa) was on average 30% higher in nts 382 than Bragg. Also, while % Ndfa in either nts 382 or Bragg was not influenced by P addition, total N and consequently, Ndfa increased. However, for Chippewa which fixed the lowest N, both % Ndfa and Ndfa were increased by P addition. We conclude that although supernodulation had an adverse effect on shoot and root growth, these reductions could not be attributed to a reduced uptake of the two major plant nutrients, N and P, neither was there evidence that the mutation had caused a greater demand for these nutrients, other than for the greater requirement of P for nodulation. ei]{gnR O D}{fnDixon}

Key words

mutant15N isotope dilutionnitrogen fixationnitrogen (N) use efficiencynodulesphosphorusphosphorus (P) use efficiencyrootssupernodulator

Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • S. F. B. N. Gunawardena
    • 1
  • S. K. A. Danso
    • 2
  • F. Zapata
    • 3
  1. 1.Faculty of AgricultureUniversity of RuhunaMapalamaSri Lanka
  2. 2.Joint FAO/IAEA Division of Nuclear Techniques in Food and AgricultureViennaAustria
  3. 3.IAEA Laboratories in SeibersdorfAustria