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Soil aeration is a key parameter for sustainable and productive agriculture. The intensification of agricultural activity in Greenland involves land use (LU) and LU change, affecting the soil-air phase. The combined effects of natural compaction (bulk density, ρ b ), texture (texture uniformity index; TUI), and LU on the soil-air phase of subarctic soils are not well known. This study aims to identify and compare the main drivers for air-filled porosity (ε) and soil-structure changes within and across sites in Greenland and Denmark. We analyzed comprehensive data sets of ε, relative gas diffusivity D p /D o ), and air-permeability (k a ) measured on intact soil samples from South Greenland (pasture) and Denmark (cultivated, urban, and forest). The mechanical robustness of the air phase was evaluated by linear models of ε as a function of ρ b (H-model). The ratio of k a to D p /D o served as a soil-structure index (Ω); the latter significantly correlated to TUI. The Greenlandic pasture soils did not show signs of well-developed soil structure (low Ω-values), whereas low H-values suggested the soils were mechanically robust compared to similar-textured cultivated soils. The soil-air characteristic curve (ε vs. pF) was parameterized, and the moisture control parameter was accurately predicted by TUI and LU (R 2 = .95). Overall, the ρ b was found to control the air-phase functions within a field. However, considering changes in ε-levels across different fields, texture, LU, and other environmental factors became statistically more relevant than ρ b . A modeled response surface for changes in ε with soil conditions may, in perspective, be useful for better-predicting gas transport in soil, both within and across fields.

Greenlandic fjords contain vast amounts of glacially derived mineral material (glacial rock flour [GRF]), which may be used to amend structureless, low‐clay, and water‐repellent agricultural soils in South Greenland and elsewhere. In this study, we investigate key physical amendment properties of GRF from 16 different deposits in South Greenland. The clay‐sized fraction varied largely (range, 0.11–0.57 kg kg−1), and the particles were mostly angular. The specific surface area (SSA) determined by either ethylene glycol monomethyl ether (EGME, polar liquid) (range, 13.32–88.06 m2 g−1) or water‐vapor adsorption (range, 10.62–63.82 m2 g−1) agreed well (r = .90) and were comparable to kaolinitic‐clay dominated cultivated soils (KA‐soils) with clay content similar to the GRFs. The cation exchange capacities (CECs) (range, 4.25–21.91 cmol kg−1) were similar to or higher than those of the KA‐soils. The water content at the permanent wilting point (PWP) for the GRFs were considerably lower than those of the KA‐soils. The addition of 5% GRF to a sandy soil from Greenland showed a tendency (although not statistically significant) to increase plant available water (PAW). However, very high GRF addition (10 and 15%) significantly decreased the PAW. The specific surface charge (CEC/SSA) of the GRFs were higher than for comparable KA‐soils, suggesting a good soil amendment potential. The results from this study are valuable toward designing sustainable GRF amendment strategies, matching a given cultivated soil with the right amount and type of GRF.

The warming climate is rapidly changing the circumpolar region, presenting new opportunities and challenges for agricultural production in South Greenland. The warming climate is projected to increase the frequency of drought periods, but little is known about the soil-water retention (SWR) and the plant available water (PAW) of the agricultural soils in the region. This study aimed to measure the SWR and PAW of Greenlandic agricultural soils and evaluate the effect of organic carbon (OC) and clay (CL) content using pedotransfer functions based on OC and CL. The study included 464 South Greenlandic agricultural soil samples from 20 fields with a wide distribution in clay (0.016-0.184 kg kg −1 ) and OC contents (0.006-0.254 kg kg −1 ). Pedotransfer functions were successfully developed for estimating the gravimetric water content (w) at five soil-water potentials (−1500, −100, −30, −10, and −5 kPa) and PAW. The OC content was the primary variable governing the gravimetric water content at each soil-water potential, evidenced by R 2 values consistently above 0.80.The effect of OC on the gravimetric water content at −1500 kPa was close to the range reported in the literature, but OC effects were markedly higher between −100 and −5 kPa. Overall, this study highlights a substantial effect of OC on the PAW as a 1% increase in OC increased PAW by more than 4%, which is almost twice the value of a recent meta-study. Our study highlights the potentially dominating effects of organic matter on soil-water balance and availability in high-latitude agriculture.