A novel heat-pulse probe for measuring soil thermal conductivity: Field test under different tillage practices

Accurate soil thermal conductivity (lambda) measurements are needed in experimental agri-environmental research. This study design and build of new heat-pulse probe (HPP) based on transient state technology to measure lambda. The HPP consists of three main components: an electronic control system, a measurement chamber, and sample rings. The performance of the new HPP for in-situ lambda measurements is compared to estimates from measurable soil physical properties (pedotransfer function). Tests were conducted in clay loam and loam soils at three depths. lambda measurements by the HPP were affected by tillage practice, fertilizer treatment, soil depth, and soil type. No significant differences in lambda measurements by the HPP and estimates from a pedotransfer function were found between tillage practices. There were positive correlations between their values at three soil depths: R2 = 0.92 at 0-5 cm depth, and R2 = 0.88 at both 5-10 and 10-15 cm depths. The standard deviation from the HPP mea-surements were 0.061, 0.077, and 0.080 W.m- 1.K-1 at 0-5, 5-10, and 10-15 cm depths, respectively. In contrast, the pedotransfer function estimates had standard deviations of 0.085, 0.660, and 0.083 W.m- 1.K- 1, respectively. It was found that conventional tillage increases temperature flow in soils compared to no-tillage because of decreasing soil bulk density (rho b) and consequently higher porosity. The proposed HPP is a low-cost and energy-efficient device, with wide applicability under a range of conditions. It is highly recom-mended for measuring lambda clay loam and loam soils; however, more research is needed to determine its value with other soil types.