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This article in AJ

  1. Vol. 64 No. 5, p. 597-599
    Received: Dec 10, 1971

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Effect of Inoculum Size on Nodulation of Glycine max (L.) Merril, Variety Ford1

  1. R. W. Weaver and
  2. L. R. Frederick2



A criterion for determining adequacy of inoculation of Glycine max by Rhizobium japonicum is needed for testing of commercial inoculants and for determining adequacy of nodulation. This study was undertaken to determine the inoculum level needed for maximum nitrogen fixation of Glycine max and to find a qualitative nodulation pattern that would be useful in recognizing good nodulation. To accomplish this end, soybeans were inoculated and grown hi pots containing sand or soil in the greenhouse. Inoculation levels up to 2.4 ✕ 105 and 1.4 ✕ 107 Rhizobium japonicum cells per seed were used for soil- and sand-grown plants respectively. Taproot nodulation was still increasing at the highest inoculum level in soil and sand, but lateral root nodulation had leveled off. Maximum total nitrogen fixed in plant tops was achieved at inoculation levels of 2 ✕ 103 and 1 ✕ 105 cells per seed for soil- and sand-grown plants, respectively. At these inoculation levels at least four taproot nodules were formed. Results suggest that taproot nodulation of soybeans is a qualitative characteristic that may be useful in determining the adequacy of nodulation and may indicate abundance of rhizobia for a soybean variety.

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