Abstract

Soil organic carbon (SOC) in arable topsoil is known to have beneficial effects on soil physical properties that are important for soil fertility. The effects of SOC content on soil aggregate stability have been well documented; however, few studies have investigated its relationship with the soil pore structure, which has a strong influence on water dynamics and biogeochemical cycling. In the present study, we examined the relationships between SOC and clay contents and pore size distributions (PSDs) across an arable field with large spatial variations in topsoil SOC and clay contents by combining X-ray tomography and measurements of soil water retention. Additionally, we investigated the relationships between fractionated SOC, reactive Fe and Al oxide contents and soil pore structure. We found that porosities in the 0.2-720 mu m diameter class were positively correlated with SOC content. A unit increase of SOC content was associated with a relatively large increase in porosity in the 0.2-5 and 480-720 mu m diameter classes, which indicates that enhanced SOC content would increase plant available water content and unsaturated hydraulic conductivity. On the other hand, macroporosities (1200-3120 mu m diameter classes) and bioporosity were positively correlated with clay content but not with SOC content. Due to strong correlations between soil texture, carbon-to-nitrogen ratios and reactive iron contents, we could not separate the relative importance of these soil properties for PSDs. Reactive aluminium and particulate organic carbon contents were poorer predictors for PSDs compared with clay and SOC contents. This study provides new insights on the relations between SOC and soil pore structure in an arable soil and may lead to improved estimations of the effects of enhanced SOC sequestration on soil water dynamics and soil water supply to crops. Highlights Relations between soil organic carbon (SOC) and pore size distribution (PSD) in an arable soil were explored. We used X-ray tomography and soil water retention to quantify a wide range of PSD. There were positive correlations between SOC and porosities in 0.2-720 mu m diameter classes. Porosities in 0.2-5 and 480-720 mu m diameter classes were more strongly correlated with SOC than clay. Our results have implications for improved estimates of effects of SOC sequestration on soil water dynamics.

Keywords

arable soil; biopore; pore size distribution; reactive mineral phases; soil organic carbon; soil water retention; SOM fractionation; texture; X-ray tomography

Published in

European Journal of Soil Science
2022, Volume: 73, number: 1, article number: e13212
Publisher: WILEY

SLU Authors

• Fukumasu, Jumpei

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Jarvis, Nicholas

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Koestel, Johannes

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Kätterer, Thomas

  • Department of Ecology, Swedish University of Agricultural Sciences
    

• Larsbo, Mats

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss


UKÄ Subject classification

Soil Science


Publication identifier

DOI: https://doi.org/10.1111/ejss.13212

Permanent link to this page (URI)

https://res.slu.se/id/publ/116329