Glacial rock flour reduces the hydrophobicity of Greenlandic cultivated soils

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 (WRAREA), W-NON,W- and WR after heat treatments at 105 degrees C (WR105) and 60 degrees 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 WRAREA to the water vapor sorption isotherms (utilizing the Campbell-Shiozawa model) revealed that GRF consistently reduced the normalized WRAREA. The SI field showed the largest reduction in the normalized WRAREA, likely due to its lower OC and clay contents. Thus, GRF could reduce WR across two Greenlandic field trials.

Automated summary

Soil water repellency (WR) is common in Greenlandic cultivated fields, limiting agricultural production. The application of glacial rock flour (GRF) as a soil amendment was tested to reduce WR. The results showed that application rates of >=300 ton ha(-1) of GRF increased soil hydrophilicity, likely due to increased clay:OC ratios. GRF at rates of >=300 ton ha(-1) generally reduced WR, as indicated by decreased WR-W curve area, water content at WR cessation, and heat-treated WR. The effects of GRF were influenced by soil texture and organic carbon content. Normalizing WR data to water vapor sorption isotherms revealed consistently reduced normalized WR area with GRF application, with the largest reduction in the field with lower organic carbon and clay content. Therefore, GRF can reduce WR in Greenlandic field trials.