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This article in SSSAJ

  1. Vol. 42 No. 6, p. 926-930
    Received: Dec 30, 1977
    Accepted: July 28, 1978

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Partial Substitution of Mycorrhizal Fungi for Phosphorus Fertilization in the Greenhouse Culture of Citrus1

  1. J. A. Menge,
  2. C. K. Labanauskas,
  3. E. L. V. Johnson and
  4. R. G. Platt2



The interaction between P fertilization of citrus and the mycorrhizal fungus Glomus fasciculatus was examined in a greenhouse study. A low fertility loamy sand (4.6 ppm P) was provided with all necessary soil nutrients except P. This soil received superphosphate [Ca(H2PO4)2 · H2O] at rates of 0, 6, 28, 56, 278, and 556 ppm of P. Seven replicate mycorrhizal and nonmycorrhizal Brazilian sour orange and Troyer citrange seedlings were grown at each P fertility level. After 5 months, mycorrhizal sour orange which received 0 fertilizer P were similar in size to non-mycorrhizal sour orange which were fertilized with 278 ppm P. Mycorrhizal citrange which received 0 fertilizer P were similar in size to nonmycorrhizal citrange which were fertilized with 56 ppm P. Dry weights of mycorrhizal sour orange seedlings were significantly greater than nonmycorrhizal sour orange seedlings when fertilized with 0, 6, 28, and 56 ppm P (947, 1089, 347, and 253% greater, respectively). Dry weights of mycorrhizal citrange seedlings were significantly greater than nonmycorrhizal citrange seedlings only when fertilized with 0 and 6 ppm P (746 and 300% greater, respectively). The %P in leaves of both citrus cultivars was enhanced by the mycorrhizal association at all P fertility levels. Variation in absorption of K, Mg, and Na by the citrus cultivars appeared to be primarily influenced by P concentrations of the seedlings. Variation in absorption of Zn, Cu, and Mn appeared to be influenced by both P concentrations of the seedlings and the presence of the mycorrhizal fungus. The number of G. fasciculatus spores/cm3 of soil which were associated with inoculated plants decreased with increasing P fertility levels. With mycorrhizal sour orange, numbers of spores decreased from 10.1 spores/cm3 soil at 56 ppm P soil to 0 spores/cm3 soil with plants at 556 ppm P. With mycorrhizal citrange, numbers of spores decreased from 5.7 spores/cm3 soil at 28 ppm P to 0 spores/cm3 soil at 56 ppm P. No correlation was found between soil P or % P in leaves, roots or stems of seedlings and the elimination of spore production.

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