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Soil compaction: effects on soil hydraulic properties and preferential water flow

Mossadeghi Björklund, Mona (2020). Soil compaction: effects on soil hydraulic properties and preferential water flow. Sveriges lantbruksuniv.
ISBN 978-91-7760-616-1
eISBN 978-91-7760-617-8
[Licentiate thesis]

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Abstract

Soil compaction caused by passage of agricultural machinery over the surface is an issue in many agricultural soils with a high clay content. Compaction is known to modify soil pore structure and soil hydraulic properties, but can also affect the occurrence of preferential flow. Water flow through preferential flow pathways can facilitate transport of fertilisers, pesticides and contaminants to groundwater, creating harmful environmental problems. In two complementary studies, this thesis examined soil hydraulic properties and preferential water flow on soil cores sampled in the field and quantified flow patterns in situ at two sites approximately 300 m apart in central Sweden. One year after compaction of field plots, X-ray computed tomography (CT) imaging was used to visualise and quantify soil pore structures in soil columns taken from the subsoil (30-50 cm depth). Degree of preferential water flow and transport were derived from non-reactive tracer breakthrough curves. Dye tracing experiments were performed in the field and different soil mechanical and hydraulic properties were measured to help explain the dye patterns.
Contrasting effects of wheel traffic were observed at the two neighbouring sites. Thus, even quite small differences in initial soil and site conditions can significantly influence the extent to which applied compaction stresses affect the connectivity of structural pore space in soil and, consequently, water flow patterns. These results contradict previous findings of an increase in preferential flow following soil compaction. This discrepancy in results was analysed with the help of a conceptual model, which suggested that preferential flow is greatest at some intermediate level of compaction at which macropore continuity is still maintained, despite reductions in macroporosity. The model also illustrated how compaction, and subsequent recovery from compaction, might affect susceptibility to preferential flow and surface runoff. To prevent subsoil compaction, it is important to consider soil conditions at the time of trafficking, which can significantly influence the effect of compaction on soil pore connectivity and associated water flow.

Authors/Creators:Mossadeghi Björklund, Mona
Title:Soil compaction: effects on soil hydraulic properties and preferential water flow
Year of publishing :2020
Number of Pages:47
Publisher:Department of Soil and Environment, Swedish University of Agricultural Sciences, Department of Soil and Environment
ISBN for printed version:978-91-7760-616-1
ISBN for electronic version:978-91-7760-617-8
Language:English
Publication Type:Licentiate thesis
Article category:Other scientific
Version:Published version
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Environmental Sciences (social aspects to be 507)
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Soil Science
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 405 Other Agricultural Sciences > Environmental Sciences related to Agriculture and Land-use
Keywords:Subsoil compaction, air permeability, breakthrough curve, CT-imaging, penetration resistance, saturated hydraulic conductivity, dye tracing, macroporosity, soil pore structure, water flow
URN:NBN:urn:nbn:se:slu:epsilon-p-107318
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-107318
ID Code:17498
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Dept. of Soil and Environment
(S) > Dept. of Soil and Environment
Deposited By: SLUpub Connector
Deposited On:08 Sep 2020 06:54
Metadata Last Modified:16 Sep 2020 10:38

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