Gas diffusion characteristics of agricultural soils from South Greenland

• Published in: Soil Science Society of America Journal
• Main Authors: Weber, Peter L., de Jonge, Lis Wollesen, Greve, Mogens H., Norgaard, Trine, Moldrup, Per
• Other Authors: Teknologi og Produktion, Det Frie Forskningsråd
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2020
• Subjects: Arctic; Greenland; greenlandic
• Online Access: http://dx.doi.org/10.1002/saj2.20114; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fsaj2.20114; https://onlinelibrary.wiley.com/doi/pdf/10.1002/saj2.20114; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/saj2.20114

Abstract The Arctic is warming at twice the global average, which may impact agricultural production in Greenland. Therefore knowledge of the functional properties of Greenlandic soil resources is necessary. The relative soil gas diffusivity [the soil gas diffusion coefficient ( D p )–free‐air diffusion coefficient ( D o ) ratio] is the chief parameter controlling gas transport in soils. Predictions of D p / D o are needed to estimate root zone aeration and terrestrial greenhouse gas fluxes. We used existing models to analyze the D p / D o of soils from Greenlandic fields and a pore connectivity index ( C ip ) to infer their degree of structural development and identify the main parameters controlling D p / D o . In total, 201 × 3 intact 100‐cm 3 soil samples were sampled across six fields with clay and organic C contents of 0.016 to 0.089 and 0.016 to 0.105 kg kg −1 , respectively. The D p / D o was measured with the one‐chamber nonsteady‐state method at soil water potentials between –10 and –1,000 cm H 2 O. Accurate determination of total porosity (Φ) was ensured by calibrating a particle density model on 129 samples. The soils exhibited a less developed structure and highly tortuous pore networks, resulting in low D p / D o as a function of air‐filled porosity (ε). Density‐corrected models with air saturation (ε/Φ) reduced the RMSE. Furthermore, C ip at –1,000 cm H 2 O soil water potential increased linearly with dry bulk density (ρ b ), suggesting that ρ b is a key controller of D p / D o , which is important for planning cultivation practices for Southern Greenlandic soils. Lastly, we found that an air saturation >35% is required for adequate soil aeration.