Do Biofuel and Cover Crops Affect Soil Thermal Properties?.

Heat transport is an important factor that can influence the soil environment. The objective of this study was to determine if perennial biofuel and cover crops could alter soil thermal properties. Experimental treatments included two levels of cover crops (cover crops [CC] vs. no cover crops [NC]) collectively called row crops (RC) and two treatments of biofuel crops. Cover crops used included Cereal rye (Secale cereal L.), Hairy vetch (Vicia villosa subsp. villosa) and Austrian winter pea (Pisum sativum subsp. arvense). The two biofuel treatments included perennial biofuel crops (PB): giant miscanthus (Miscanthus x giganteus J.M. Greef & Deuter ex Hodkinson & Renvoize) and switchgrass (Panicum virgatum L.), both collectively called PB. Soil samples were collected at 10 cm depth increments from the soil surface to a depth of 30 cm. Soil thermal properties (thermal conductivity [λ], volumetric heat capacity [C_V], and thermal diffusivity [D]) and volumetric water content (θ) were determined at 0, -33, -100 and -300 kPa soil water matric potentials. Additionally, bulk density and soil organic carbon (SOC) were determined. Results showed that PB had 11% higher C_V at saturation probably due to significantly higher θ and SOC compared to RC management. Cover crops had 13% higher C_V at saturation probably due to significantly higher θ and SOC compared to no cover crop management. Row crops had significantly higher λ and D compared to perennial biofuel crops. Results from the current study imply that CC and PB can change soil thermal properties by reducing λ and D and increasing C_V under laboratory conditions.