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Effects of soil compaction on plant growth, phosphorus uptake and morphological characteristics of vesicular–arbuscular mycorrhizal colonization of Trifolium subterraneum

Published online by Cambridge University Press:  01 February 1997

H. NADIAN ,
S. E. SMITH ,
A. M. ALSTON  and
R. S. MURRAY
H. NADIAN
Affiliation:
Department of Soil Science, Waite Agricultural Institute, The University of Adelaide, Glen Osmond, SA 5064, Australia
S. E. SMITH
Affiliation:
Department of Soil Science, Waite Agricultural Institute, The University of Adelaide, Glen Osmond, SA 5064, Australia
A. M. ALSTON
Affiliation:
Department of Soil Science, Waite Agricultural Institute, The University of Adelaide, Glen Osmond, SA 5064, Australia
R. S. MURRAY
Affiliation:
Department of Soil Science, Waite Agricultural Institute, The University of Adelaide, Glen Osmond, SA 5064, Australia
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Abstract

We investigated the effect of soil compaction and phosphorus (P) application on morphological characteristics of mycorrhizal colonization and growth responses, to determine the reasons for reduced responses observed in our previous work with compacted soil. Growth, phosphorus (P) uptake and intensity of vesicular–arbuscular (VA) mycorrhizal colonization were studied in clover plants (Trifolium subterraneum L.) with and without VA mycorrhizal colonization at two P applications and three levels of soil compaction. Phosphorus was supplied either at constant mass concentration (mg P kg−1 soil) or at constant volume concentration (mg P dm−3 soil). Increasing bulk density of the soil from 1·1 to 1·6 Mg m−3 significantly decreased root length and shoot d. wt, but increased the diameter of both main axes and first order lateral roots regardless of P application. Total P uptake and shoot d. wt of clover plants colonized by Glomus intraradices (Schenck & Smith) were significantly greater than those of non-mycorrhizal plants at all levels of soil compaction and both P applications. However, soil compaction to a bulk density of 1·6 Mg m−3 (penetrometer resistance = 3·5 MPa at a matric potential of −33 kPa) significantly decreased mycorrhizal growth response. There was no evidence that the increased volume concentration of P at high bulk densities was responsible for the reduced responses. Soil compaction had no significant effect on the fraction of root length containing arbuscules and vesicles, but total root length colonized by arbuscules, vesicles or by any combination of arbuscules, vesicles and intra-radical hyphae significantly decreased as soil compaction was increased. The air-filled porosity of highly compacted soil, which varied from 0·07 to 0·11 over the range of matric potentials encountered (−33 and −100 kPa), had no significant effect on the intensity of internal colonization.

Keywords

Arbusculecompactionmycorrhizal growth responseP uptakevesicle
Type
Research Article
Information
The New Phytologist , Volume 135 , Issue 2 , February 1997 , pp. 303 - 311
Copyright
Trustees of the New Phytologist 1997

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