TY - JOUR

T1 - Variations in pore size and contact angle distributions control rhizosphere rewetting

AU - Benard, P.

AU - Bachmann, J.

AU - Zarebanadkouki, M.

AU - Schlüter, S.

AU - Blaser, S. R.G.A.

AU - Kaestner, A.

AU - Carminati, A.

N1 - Funding Information: Financial support provided by the German Research Foundation DFG (316989341 and 403640522) for this project is greatly appreciated. Open access funding provided by ETH Zurich.

PY - 2023/9

Y1 - 2023/9

N2 - Rhizosphere wettability decreases upon severe drying leading to periods of prolonged low water content around roots after precipitation or irrigation. These observations were explained by the temporal hydrophobic character of mucilage, while structural alterations of the pore space caused by mucilage, such as pore clogging, remained mostly unexplored. In this study, time-series neutron radiography and a pore network model were used to assess the impact of pore geometry and wettability on water flow following the addition of mucilage in a sand substrate. To do so, we monitored the capillary rise of ethanol and water separately for mucilage contents, ranging from 0.0 to 2.0 mg g−1. A pore network model was developed to analyze the impact of alterations in pore geometry and wettability. Results are compared with analytical solutions of the Lucas-Washburn equation. Rewetting dynamics were explained by a combination of a decrease in effective pore throat size and a global decrease in wettability. The local distribution of wettability, however, appeared of minor importance as dynamics of water imbibition could be matched by a uniform effective contact angle. For 0.1 mg g−1 mucilage content increased wettability was predicted for both approaches: the analytical solution and the pore network model fit. At larger contents, a decrease in wettability occurred which was accompanied by a decrease in derived effective pore and pore throat size. On a minute scale, rewetting appeared to steadily progress at all mucilage contents with accelerated rewetting observed at 0.6 mg g−1 likely related to an increased wetting front length. This study highlights the importance of mucilage on pore geometry in combination with wettability modifications in the rhizosphere. Aside from rhizosphere rewetting, the presented approach provides an opportunity to investigate further wettability-related processes in other soil environments on various spatial scales.

AB - Rhizosphere wettability decreases upon severe drying leading to periods of prolonged low water content around roots after precipitation or irrigation. These observations were explained by the temporal hydrophobic character of mucilage, while structural alterations of the pore space caused by mucilage, such as pore clogging, remained mostly unexplored. In this study, time-series neutron radiography and a pore network model were used to assess the impact of pore geometry and wettability on water flow following the addition of mucilage in a sand substrate. To do so, we monitored the capillary rise of ethanol and water separately for mucilage contents, ranging from 0.0 to 2.0 mg g−1. A pore network model was developed to analyze the impact of alterations in pore geometry and wettability. Results are compared with analytical solutions of the Lucas-Washburn equation. Rewetting dynamics were explained by a combination of a decrease in effective pore throat size and a global decrease in wettability. The local distribution of wettability, however, appeared of minor importance as dynamics of water imbibition could be matched by a uniform effective contact angle. For 0.1 mg g−1 mucilage content increased wettability was predicted for both approaches: the analytical solution and the pore network model fit. At larger contents, a decrease in wettability occurred which was accompanied by a decrease in derived effective pore and pore throat size. On a minute scale, rewetting appeared to steadily progress at all mucilage contents with accelerated rewetting observed at 0.6 mg g−1 likely related to an increased wetting front length. This study highlights the importance of mucilage on pore geometry in combination with wettability modifications in the rhizosphere. Aside from rhizosphere rewetting, the presented approach provides an opportunity to investigate further wettability-related processes in other soil environments on various spatial scales.

KW - Mucilage

KW - Neutron imaging

KW - Pore network model

KW - Rhizosphere

KW - Soil wettability

UR - http://www.scopus.com/inward/record.url?scp=85164240185&partnerID=8YFLogxK

U2 - 10.1016/j.geoderma.2023.116576

DO - 10.1016/j.geoderma.2023.116576

M3 - Article

AN - SCOPUS:85164240185

VL - 437

JO - GEODERMA

JF - GEODERMA

SN - 0016-7061

M1 - 116576

ER -