The University of Southampton
University of Southampton Institutional Repository

Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis

Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis
Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis

Aims: Rhizodeposits collected from hydroponic solutions with roots of maize and barley, and seed mucilage washed from chia, were added to soil to measure their impact on water retention and hysteresis in a sandy loam soil at a range of concentrations. We test the hypothesis that the effect of plant exudates and mucilages on hydraulic properties of soils depends on their physicochemical characteristics and origin. Methods: Surface tension and viscosity of the exudate solutions were measured using the Du Noüy ring method and a cone-plate rheometer, respectively. The contact angle of water on exudate treated soil was measured with the sessile drop method. Water retention and hysteresis were measured by equilibrating soil samples, treated with exudates and mucilages at 0.46 and 4.6 mg g−1 concentration, on dialysis tubing filled with polyethylene glycol (PEG) solution of known osmotic potential. Results: Surface tension decreased and viscosity increased with increasing concentration of the exudates and mucilage in solutions. Change in surface tension and viscosity was greatest for chia seed exudate and least for barley root exudate. Contact angle increased with increasing maize root and chia seed exudate concentration in soil, but not barley root. Chia seed mucilage and maize root rhizodeposits enhanced soil water retention and increased hysteresis index, whereas barley root rhizodeposits decreased soil water retention and the hysteresis effect. The impact of exudates and mucilages on soil water retention almost ceased when approaching wilting point at −1500 kPa matric potential. Conclusions: Barley rhizodeposits behaved as surfactants, drying the rhizosphere at smaller suctions. Chia seed mucilage and maize root rhizodeposits behaved as hydrogels that hold more water in the rhizosphere, but with slower rewetting and greater hysteresis.

Contact angle, Hysteresis, Root exudate, Seed exudate, Soil water retention, Surface tension, Viscosity
0032-079X
Naveed, M.
ffa04925-7d0a-42fa-b95b-548fe3e4e2db
Ahmed, M. A.
8444f360-bd3f-4fbd-8dbb-82c26180a8cb
Benard, P.
4b9f145f-a50c-4e76-b036-9cef367aa8c7
Brown, L. K.
c10f9ba0-4584-433a-bd87-926ab197a64b
George, T. S.
6b957175-f0b0-4456-87e3-241040c31cf8
Bengough, A. G.
ac1f754e-002c-44f6-8907-8771a4cd1fd3
Roose, T.
3581ab5b-71e1-4897-8d88-59f13f3bccfe
Koebernick, N.
118c4e45-02d8-42da-84c8-8ee4fac140ad
Hallett, P. D.
2e6a4596-83d9-4aeb-bb84-025c3660a536
Naveed, M.
ffa04925-7d0a-42fa-b95b-548fe3e4e2db
Ahmed, M. A.
8444f360-bd3f-4fbd-8dbb-82c26180a8cb
Benard, P.
4b9f145f-a50c-4e76-b036-9cef367aa8c7
Brown, L. K.
c10f9ba0-4584-433a-bd87-926ab197a64b
George, T. S.
6b957175-f0b0-4456-87e3-241040c31cf8
Bengough, A. G.
ac1f754e-002c-44f6-8907-8771a4cd1fd3
Roose, T.
3581ab5b-71e1-4897-8d88-59f13f3bccfe
Koebernick, N.
118c4e45-02d8-42da-84c8-8ee4fac140ad
Hallett, P. D.
2e6a4596-83d9-4aeb-bb84-025c3660a536

Naveed, M., Ahmed, M. A., Benard, P., Brown, L. K., George, T. S., Bengough, A. G., Roose, T., Koebernick, N. and Hallett, P. D. (2019) Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis. Plant and Soil. (doi:10.1007/s11104-019-03939-9).

Record type: Article

Abstract

Aims: Rhizodeposits collected from hydroponic solutions with roots of maize and barley, and seed mucilage washed from chia, were added to soil to measure their impact on water retention and hysteresis in a sandy loam soil at a range of concentrations. We test the hypothesis that the effect of plant exudates and mucilages on hydraulic properties of soils depends on their physicochemical characteristics and origin. Methods: Surface tension and viscosity of the exudate solutions were measured using the Du Noüy ring method and a cone-plate rheometer, respectively. The contact angle of water on exudate treated soil was measured with the sessile drop method. Water retention and hysteresis were measured by equilibrating soil samples, treated with exudates and mucilages at 0.46 and 4.6 mg g−1 concentration, on dialysis tubing filled with polyethylene glycol (PEG) solution of known osmotic potential. Results: Surface tension decreased and viscosity increased with increasing concentration of the exudates and mucilage in solutions. Change in surface tension and viscosity was greatest for chia seed exudate and least for barley root exudate. Contact angle increased with increasing maize root and chia seed exudate concentration in soil, but not barley root. Chia seed mucilage and maize root rhizodeposits enhanced soil water retention and increased hysteresis index, whereas barley root rhizodeposits decreased soil water retention and the hysteresis effect. The impact of exudates and mucilages on soil water retention almost ceased when approaching wilting point at −1500 kPa matric potential. Conclusions: Barley rhizodeposits behaved as surfactants, drying the rhizosphere at smaller suctions. Chia seed mucilage and maize root rhizodeposits behaved as hydrogels that hold more water in the rhizosphere, but with slower rewetting and greater hysteresis.

Text
Naveed2019_Article_SurfaceTensionRheologyAndHydro - Version of Record
Available under License Creative Commons Attribution.
Download (1MB)

More information

Accepted/In Press date: 8 January 2019
e-pub ahead of print date: 2 February 2019
Keywords: Contact angle, Hysteresis, Root exudate, Seed exudate, Soil water retention, Surface tension, Viscosity

Identifiers

Local EPrints ID: 428238
URI: http://eprints.soton.ac.uk/id/eprint/428238
ISSN: 0032-079X
PURE UUID: d68bb25f-6c1f-4fbb-be55-ffe5735f21e7
ORCID for T. Roose: ORCID iD orcid.org/0000-0001-8710-1063

Catalogue record

Date deposited: 18 Feb 2019 17:30
Last modified: 07 Oct 2020 01:55

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×