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Plant exudates may stabilize or weaken soil depending on species, origin and time

Plant exudates may stabilize or weaken soil depending on species, origin and time
Plant exudates may stabilize or weaken soil depending on species, origin and time
We hypothesized that plant exudates could either gel or disperse soil depending on their chemical characteristics. Barley (Hordeum vulgare L. cv. Optic) and maize (Zea mays L.cv. Freya) root exudates were collected using an aerated hydroponic method and compared to chia (Salvia hispanica L.) seed exudate, a commonly used root exudate analogue. Sandy loam soil passed through a 500-μm mesh was treated with each exudate at a concentration
of 4.6 mg exudate g-1 dry soil. Two sets of soil samples were prepared, One set of treated soil samples was maintained at 4oC to suppress microbial processes. To characterize the effect of decomposition, the second set of samples was incubated at 16C for 2 weeks at – 30 kPa matric potential. Gas chromatography–mass spectrometry (GC–MS) analysis of the exudates found that barley had the largest organic acid content and chia the largest content of sugars (polysaccharide-derived or free), and maize was in between barley and chia. Yield stress of amended soil samples was measured by an oscillatory strain sweep test with a cone plate rheometer. When microbial decomposition was suppressed at 4oC, yield stress increased 20-fold for chia seed exudate and two-fold for maize root exudate compared to the control, whereas for barley root exudate it decreased to half. The yield stress after 2 weeks of incubation compared to soil with suppressed microbial decomposition increased by 85% for barley root exudate, but for chia and maize it decreased to by 87% and 54%, respectively. Barley root exudation might therefore disperse soil and this could facilitate nutrient release. The maize root and chia seed exudates gelled soil, which could create a more stable soil structure around roots or seeds.
root exudate, seed exudate, viscosity, yield stress, soil dispersion, soil gelling, microbial decomposition
1351-0754
806-816
Naveed, Muhammad
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Brown, Lawrie
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Raffan, Annette
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George, Tim
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Bengough, Anthony G.
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Roose, Tiina
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Sinclair, Ian
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Koebernick, Nicolai
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Cooper, Laura
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Hallett, Paul D.
2e6a4596-83d9-4aeb-bb84-025c3660a536
Naveed, Muhammad
ffa04925-7d0a-42fa-b95b-548fe3e4e2db
Brown, Lawrie
e9b2a56b-bb20-4aea-b8b8-eae0e9122e55
Raffan, Annette
65909bd1-df87-4fc1-8c15-c2395d01dd0f
George, Tim
1f0f405e-b2ac-4d63-b922-1463d16dd777
Bengough, Anthony G.
ac1f754e-002c-44f6-8907-8771a4cd1fd3
Roose, Tiina
3581ab5b-71e1-4897-8d88-59f13f3bccfe
Sinclair, Ian
6005f6c1-f478-434e-a52d-d310c18ade0d
Koebernick, Nicolai
118c4e45-02d8-42da-84c8-8ee4fac140ad
Cooper, Laura
b8f4b942-cb87-4386-ab29-17bdd0f53ec1
Hallett, Paul D.
2e6a4596-83d9-4aeb-bb84-025c3660a536

Naveed, Muhammad, Brown, Lawrie, Raffan, Annette, George, Tim, Bengough, Anthony G., Roose, Tiina, Sinclair, Ian, Koebernick, Nicolai, Cooper, Laura and Hallett, Paul D. (2017) Plant exudates may stabilize or weaken soil depending on species, origin and time. European Journal of Soil Science, 68 (6), 806-816. (doi:10.1111/ejss.12487).

Record type: Article

Abstract

We hypothesized that plant exudates could either gel or disperse soil depending on their chemical characteristics. Barley (Hordeum vulgare L. cv. Optic) and maize (Zea mays L.cv. Freya) root exudates were collected using an aerated hydroponic method and compared to chia (Salvia hispanica L.) seed exudate, a commonly used root exudate analogue. Sandy loam soil passed through a 500-μm mesh was treated with each exudate at a concentration
of 4.6 mg exudate g-1 dry soil. Two sets of soil samples were prepared, One set of treated soil samples was maintained at 4oC to suppress microbial processes. To characterize the effect of decomposition, the second set of samples was incubated at 16C for 2 weeks at – 30 kPa matric potential. Gas chromatography–mass spectrometry (GC–MS) analysis of the exudates found that barley had the largest organic acid content and chia the largest content of sugars (polysaccharide-derived or free), and maize was in between barley and chia. Yield stress of amended soil samples was measured by an oscillatory strain sweep test with a cone plate rheometer. When microbial decomposition was suppressed at 4oC, yield stress increased 20-fold for chia seed exudate and two-fold for maize root exudate compared to the control, whereas for barley root exudate it decreased to half. The yield stress after 2 weeks of incubation compared to soil with suppressed microbial decomposition increased by 85% for barley root exudate, but for chia and maize it decreased to by 87% and 54%, respectively. Barley root exudation might therefore disperse soil and this could facilitate nutrient release. The maize root and chia seed exudates gelled soil, which could create a more stable soil structure around roots or seeds.

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Accepted/In Press date: 11 September 2017
e-pub ahead of print date: 27 October 2017
Published date: November 2017
Keywords: root exudate, seed exudate, viscosity, yield stress, soil dispersion, soil gelling, microbial decomposition

Identifiers

Local EPrints ID: 414238
URI: http://eprints.soton.ac.uk/id/eprint/414238
ISSN: 1351-0754
PURE UUID: d7c37714-1209-4bb3-97fb-8ea015cb9d36
ORCID for Tiina Roose: ORCID iD orcid.org/0000-0001-8710-1063
ORCID for Laura Cooper: ORCID iD orcid.org/0000-0003-0198-7591

Catalogue record

Date deposited: 20 Sep 2017 16:31
Last modified: 07 Oct 2020 05:50

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