Glacial rock flour reduces the hydrophobicity of Greenlandic cultivated soils

Abstract

Soil water repellency (WR) is ubiquitous across Greenlandic cultivated fields, which may constrain agricultural production. Fine-grained glacial rock flour (GRF) is available in the surrounding landscape, which could serve as a soil amendment. We tested whether the application of GRF (rates of 0, 50, 100, 300, and 500 ton ha⁻¹) reduced the WR across two field trials in South Greenland. The field trials, Upernaviarsuk (UP) and South Igaliku (SI), differed in clay (UP: 0.05–0.11 kg kg⁻¹; SI: 0.03–0.05 kg kg⁻¹) and organic carbon (OC) contents (UP: 0.04–0.13 kg kg⁻¹; SI: 0.01–0.03 kg kg⁻¹). We measured WR across gravimetric water contents (W) from oven-dry to the W where WR ceased (W_NON) to obtain whole WR-W curves. Most soils became hydrophilic around air-dry conditions at application rates of ≥300 ton ha⁻¹, likely due to increased clay:OC ratios. Application rates of ≥300 ton ha⁻¹ generally reduced the trapezoidal integrated area of the WR-W curve (WR_AREA), W_NON, and WR after heat treatments at 105°C (WR₁₀₅) and 60°C (WR₆₀). The WR₁₀₅ was significantly reduced in both fields at 500 ton ha⁻¹, while WR₆₀ was significantly reduced in UP at application rates of ≥300 ton ha⁻¹. The GRF effects were masked by texture and OC variations. Normalizing WR_AREA to the water vapor sorption isotherms (utilizing the Campbell-Shiozawa model) revealed that GRF consistently reduced the normalized WR_AREA. The SI field showed the largest reduction in the normalized WR_AREA, likely due to its lower OC and clay contents. Thus, GRF could reduce WR across two Greenlandic field trials.