Improving soil thermal conductivity measurements with a heat-pulse probe: Thermal efficiency and energy demand across tillage systems

Soil thermal conductivity (λ) is a key parameter influencing seed germination, root growth, and soil-atmosphere energy exchange. Accurate and energy-efficient in-situ measurement of λ is essential for optimising tillage practices and improving soil management. This study evaluates the thermal losses conduction (Q cond ), convection (Q conv ), and radiation (Q rad ) as well as thermal efficiency (η th ) and specific energy consumption (Q con ) of an improved heat-pulse probe (HPP) under four tillage systems: no-tillage (NT), mouldboard plough (MP), rotary harrow (RH), and subsoiler (SP). Measurements were taken at three soil depths and four heating durations. Field experiments were conducted on clay loam soil (38% clay, 42% silt. 20% sand) in a semi-arid region using a randomised complete block design. Results showed that MP consistently achieved the highest η th (86.10% at 0–10 and 20–30 cm) and lowest Q con (104.30 W m −1 K −1 at 10–20 cm), representing a trade off with λ measurement accuracy, RH provided the most accurate measurements with (RMSE=0.041 0.041 W m −1 K −1 , R 2 =0.94), while MP showed slightly lower accuracy in deeper layer (R 2 = 0.86 at 20–30 cm). SP required the most energy (128.55 W m −1 K −1 at 0–10 cm). longer heating durations reduced η th across all tillage systems due to increased thermal losses. The subsurface layer provided the most stable conditions for λ measurements. Statistical analysis confirmed significant effects of tillage systems, heating time, and depth on heat losses, λ, and η th . The HPP measurements demonstrated strong agreement with pedotransfer function estimates (R² = 0.86–0.94). The highest accuracy of the HPP occurred in the 0–10 cm layer at RH systems (RMSE = 0.041 W m −1 K −1 , MAE = 0.033 W m −1 K −1 ). The accuracy of HPP slightly declined as soil depth increased under MP and SP systems. The RH systems provided the most accurate measurements across all soil depths. In conclusion, MP combined with short heating durations provided the highest thermal efficiency and the lowest specific energy consumption, whereas RH achieved the highest agreement with the pedotransfer function (lowest RMSE and highest R²), indicating the best measurement performance. These findings provide practical guidelines for improving both the energy efficiency and measurement reliability of HPP applications in agricultural systems, with potential relevance to precision agriculture. Future research should validate the system across different soil types, climates, and cropping systems to broaden its applicability.