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Type: Journal article
Title: Root distributions of Australian herbaceous perennial legumes in response to phosphorus placement
Author: Denton, M.
Sasse, C.
Tibbett, M.
Ryan, M.
Citation: Functional Plant Biology: an international journal of plant function, 2006; 33(12):1091-1102
Publisher: C S I R O Publishing
Issue Date: 2006
ISSN: 1445-4408
Statement of
Matthew D. Denton, Camille Sasse, Mark Tibbett, Megan H. Ryan
Abstract: Many Australian plant species have specific root adaptations for growth in phosphorus-impoverished soils, and are often sensitive to high external P concentrations. The growth responses of native Australian legumes in agricultural soils with elevated P availability in the surface horizons are unknown. The aim of these experiments was to test the hypothesis that increased P concentration in surface soil would reduce root proliferation at depth in native legumes. The effect of P placement on root distribution was assessed for two Australian legumes, Kennedia prorepens F. Muell. and Lotus australis Andrews, and the exotic Medicago sativa L. Three treatments were established in a low-P loam soil: amendment of 0.15 g mono-calcium phosphate in either (i) the top 50 mm (120 µg P g–1) or (ii) the top 500 mm (12 µg P g⁻¹) of soil, and an unamended control. In the unamended soil M. sativa was shallow rooted, with 58% of the root length of in the top 50 mm. K. prorepens and L. australis had a more even distribution down the pot length, with only 4 and 22% of their roots in the 0–50 mm pot section, respectively. When exposed to amendment of P in the top 50 mm, root length in the top 50 mm increased 4-fold for K. prorepens and 10-fold for M. sativa, although the pattern of root distribution did not change for M. sativa. L. australis was relatively unresponsive to P additions and had an even distribution of roots down the pot. Shoot P concentrations differed according to species but not treatment (K. prorepens 2.1 mg g⁻¹, L. australis 2.4 mg gv, M. sativa 3.2 mg g⁻¹). Total shoot P content was higher for K. prorepens than for the other species in all treatments. In a second experiment, mono-ester phosphatases were analysed from 1-mm slices of soil collected directly adjacent to the rhizosphere. All species exuded phosphatases into the rhizosphere, but addition of P to soil reduced phosphatase activity only for K. prorepens. Overall, high P concentration in the surface soil altered root distribution, but did not reduce root proliferation at depth. Furthermore, the Australian herbaceous perennial legumes had root distributions that enhanced P acquisition from low-P soils.
Keywords: alfalfa
Kennedia prorepens
Lotus australis
Medicago sativa
Rights: © CSIRO 2006
DOI: 10.1071/FP06176
Appears in Collections:Agriculture, Food and Wine publications
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