Effect of soil properties on growth promotion of wheat by Penicillium radicum
S. A. Wakelin A A , R. A. Warren A and M. H. Ryder AA CSIRO Land and Water, PMB 2, Glen Osmond, SA 5064, Australia.
B Corresponding author. Email: Steven.Wakelin@csiro.au
Australian Journal of Soil Research 42(8) 897-904 https://doi.org/10.1071/SR04035
Submitted: 11 March 2004 Accepted: 19 July 2004 Published: 14 December 2004
Abstract
Penicillium radicum is a phosphate-solubilising fungus with plant growth promoting (PGP) activity. The widespread agronomic use of P. radicum as an inoculant is dependent on the accurate prediction of conditions where PGP response will occur. Therefore, the effect of soil physicochemical and biotic factors on PGP of wheat by P. radicum was investigated. In the first experiment, PGP was assayed in 10 soils with differing physicochemical properties. Each soil was tested with and without treatment with hydroxyapatite—an insoluble form of calcium phosphate used to increase the level of total inorganic P available for microbial solubilisation. Inoculation of wheat with P. radicum significantly (P < 0.05) increased plant growth in 4 of the 10 soils tested. The magnitude of the PGP response varied with soil type, and ranged from 8.5% (plant height, Avon soil) to 75% (plant weight, Mingenew soil). Most soil properties had little influence on PGP, with only low soil fertility (N and/or P) identified as a strong indicator of PGP by P. radicum. When detected, PGP was strongest in acidic soil conditions, although PGP was observed in neutral and alkaline soils. Virtually no interactions were detected between addition of hydroxyapatite to the soil and P. radicum inoculation. The second experiment tested PGP in 3 soils previously found to be non-responsive to inoculation, before and after sterilisation by γ-irradiation. Soil biological factors affected PGP by P. radicum in 2 of the 3 soils tested. In these soils, removal of biological factor(s) increased (P < 0.05 and P < 0.1) PGP by P. radicum. These experiments have shown that large and significant increases in plant growth promotion can be achieved through seed inoculation with P. radicum. However, both abiotic and biotic soil properties play a critical role in determining the success of inoculation. P. radicum-stimulated PGP occurred in infertile soils, with a stronger effect in acidic soil conditions. Furthermore, soil biological factors can have an important role in regulating PGP by P. radicum.
Additional keywords: Triticum aestivum, hydroxyapatite, phosphorus, inoculant.
Acknowledgments
This project is funded by the Grains Research & Development Corporation of Australia (project CS0223) and Bio-Care Technology Pty Ltd, Somersby, NSW (financial and in kind support for this project). Samples of soils were obtained with the help of Mr Charles Kidd (Wesfarmers Landmark), Mr John Coppi (CSIRO Land and Water), Mr Gavin Dunn (Four Leaf Milling Pty Ltd, Tarlee, S. Aust.), and Dr Bob Holloway (South Australian Research and Development Institute, Minnipa). Dr Rob Fitzpatrick (CSIRO Land and Water) and Mr David Maschmedt (Department of Water, Land and Biodiversity Conservation, South Australia) provided invaluable assistance in soil taxonomy, and Dr Mike McLaughlin (CSIRO Land and Water) on soil P chemistry. Drs Rebecca Hamon and Elizabeth Drew (CSIRO Land and Water) and 2 anonymous referees provided useful comments and criticism on the manuscript.
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