Soil thermal properties: influence of no-till cover crops

Soil thermal properties, which determine heat transport, can influence soil health parameters and crop productivity. The objective of this study was to evaluate the 2-year effects of no-till cover crops (CCs) and no-till no cover crop (NC) on soil thermal properties (thermal conductivity (lambda), volumetric heat capacity (C-V), and thermal diffusivity (D)). Two levels of CCs were used for this study: CC versus NC. The CCs included crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia villosa Roth.), winter peas (Lathyrus hirsutus L.), oats (Avena sativa), winter wheat (Triticum aestivum L.), triticale (Triticale hexaploide Lart.), flax (Linum usitassimum L.), and barley (Hordeum vulgare L.). Soil samples were collected at 0-10, 10-20, and 20-30 cm depths and their lambda, C-V, and D were measured in the laboratory. Additionally, soil organic carbon, bulk density (BD), and volumetric water content (circle minus) at saturation, -33 kPa, and -100 kPa soil water pressures were measured. Results showed that BD was 18% and 14% higher under CC compared with NC management during 2021 and 2022, respectively. Furthermore, circle minus at all measured soil water pressures was slightly higher under CC compared with NC management during both years. As a result, lambda and D were significantly higher under NC compared with CC management, while C-V was significantly higher under CC compared with NC management, during both years and at all measured soil water pressures. Generally, soil thermal properties were directly proportional to circle minus, suggesting that circle minus may be the most important factor influencing soil thermal properties.