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Rhizosphere-scale quantification of hydraulic and mechanical properties of soil impacted by root and seed exudates

Rhizosphere-scale quantification of hydraulic and mechanical properties of soil impacted by root and seed exudates
Rhizosphere-scale quantification of hydraulic and mechanical properties of soil impacted by root and seed exudates
Using rhizosphere-scale physical measurements we test the hypothesis that plant exudates gel together soil particles and on drying they enhance soil water repellency. Barley and maize root exudates were compared with chia seed exudate, a commonly used root exudate analogue. Sandy loam and clay loam soils were treated with root exudates at 0.46 and 4.6 mg exudate g-1 dry soil, and chia seed exudate at 0.046, 0.46, 0.92, 2.3 and 4.6 mg exudate g-1 dry soil. Soil hardness and modulus of elasticity were measured at -10 kPa matric potential using a 3 mm diameter spherical indenter. Water sorptivity and repellency index of air-dry soil were measured using a miniaturized infiltrometer device with a 1 mm tip radius. Soil hardness increased by 28% for barley root exudate, 62% for maize root exudate, and 86% for chia seed exudate at 4.6 mg g-1 concentration for sandy loam soil. For a clay loam soil, root exudates did not affect soil hardness, whereas chia seed exudate increased soil hardness by 48% at 4.6 mg g-1concentration. Soil water repellency increased by 48% for chia seed exudate and 23% for maize root exudate, but not for barley root exudate at 4.6 mg g-1 concentration for sandy loam soil. For clay loam soil, chia seed exudate increased water repellency by 45%, whereas root exudates did not affect water repellency at 4.6 mg g-1concentration. Water sorptivity and repellency were both correlated with hardness, presumably due to the combined influence of exudates on hydrological and mechanical properties of soils.
Root exudate, seed exudate, rhizosphere-scale indenter and infiltrometer, soil mechanical stability, soil water repellency
1539-1663
1-12
Naveed, M.
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Brown, L.K.
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Raffan, A.C.
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George, T.S.
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Bengough, A.G.
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Roose, T.
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Sinclair, I.
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Koebernick, N.
118c4e45-02d8-42da-84c8-8ee4fac140ad
Cooper, L.
b8f4b942-cb87-4386-ab29-17bdd0f53ec1
Hallett, P.D.
b027edfe-728c-4d09-bbbd-4061e6373ef6
Naveed, M.
ffa04925-7d0a-42fa-b95b-548fe3e4e2db
Brown, L.K.
16a9fa3b-730a-4546-a9fd-a2c0a9267a40
Raffan, A.C.
65909bd1-df87-4fc1-8c15-c2395d01dd0f
George, T.S.
a506ae83-5218-40c6-b582-7243465df9fa
Bengough, A.G.
ac1f754e-002c-44f6-8907-8771a4cd1fd3
Roose, T.
3581ab5b-71e1-4897-8d88-59f13f3bccfe
Sinclair, I.
6005f6c1-f478-434e-a52d-d310c18ade0d
Koebernick, N.
118c4e45-02d8-42da-84c8-8ee4fac140ad
Cooper, L.
b8f4b942-cb87-4386-ab29-17bdd0f53ec1
Hallett, P.D.
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Naveed, M., Brown, L.K., Raffan, A.C., George, T.S., Bengough, A.G., Roose, T., Sinclair, I., Koebernick, N., Cooper, L. and Hallett, P.D. (2017) Rhizosphere-scale quantification of hydraulic and mechanical properties of soil impacted by root and seed exudates. Vadose Zone Journal, 17 (1), 1-12. (doi:10.2136/vzj2017.04.0083). (In Press)

Record type: Article

Abstract

Using rhizosphere-scale physical measurements we test the hypothesis that plant exudates gel together soil particles and on drying they enhance soil water repellency. Barley and maize root exudates were compared with chia seed exudate, a commonly used root exudate analogue. Sandy loam and clay loam soils were treated with root exudates at 0.46 and 4.6 mg exudate g-1 dry soil, and chia seed exudate at 0.046, 0.46, 0.92, 2.3 and 4.6 mg exudate g-1 dry soil. Soil hardness and modulus of elasticity were measured at -10 kPa matric potential using a 3 mm diameter spherical indenter. Water sorptivity and repellency index of air-dry soil were measured using a miniaturized infiltrometer device with a 1 mm tip radius. Soil hardness increased by 28% for barley root exudate, 62% for maize root exudate, and 86% for chia seed exudate at 4.6 mg g-1 concentration for sandy loam soil. For a clay loam soil, root exudates did not affect soil hardness, whereas chia seed exudate increased soil hardness by 48% at 4.6 mg g-1concentration. Soil water repellency increased by 48% for chia seed exudate and 23% for maize root exudate, but not for barley root exudate at 4.6 mg g-1 concentration for sandy loam soil. For clay loam soil, chia seed exudate increased water repellency by 45%, whereas root exudates did not affect water repellency at 4.6 mg g-1concentration. Water sorptivity and repellency were both correlated with hardness, presumably due to the combined influence of exudates on hydrological and mechanical properties of soils.

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Accepted/In Press date: 15 October 2017
Keywords: Root exudate, seed exudate, rhizosphere-scale indenter and infiltrometer, soil mechanical stability, soil water repellency

Identifiers

Local EPrints ID: 415075
URI: http://eprints.soton.ac.uk/id/eprint/415075
ISSN: 1539-1663
PURE UUID: abf2f351-809a-4e74-a17d-1eea29cb68c7
ORCID for T. Roose: ORCID iD orcid.org/0000-0001-8710-1063
ORCID for L. Cooper: ORCID iD orcid.org/0000-0003-0198-7591

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Date deposited: 25 Oct 2017 16:30
Last modified: 08 Oct 2020 04:37

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Contributors

Author: M. Naveed
Author: L.K. Brown
Author: A.C. Raffan
Author: T.S. George
Author: A.G. Bengough
Author: T. Roose ORCID iD
Author: I. Sinclair
Author: N. Koebernick
Author: L. Cooper ORCID iD
Author: P.D. Hallett

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