2021 journal article
Root influences on soil bulk density measurements with thermo-time domain reflectometry
GEODERMA, 403.
β’ Root influences on soil bulk density measurements with thermo-TDR technique are quantified. β’ The extended de Vires heat capacity model is used to account for the root effects. β’ A critical root density that affects thermo-TDR measurements is determined. The thermo-TDR (time domain reflectometry) technique has been applied for measuring soil bulk density (Ο b ) in-situ. However, the accuracy of thermo-TDR measured Ο b data, as influenced by plant roots, has not been studied. In this study, we applied the extended de Vries heat capacity model to examine the influences of roots on thermo-TDR sensor performance for measuring Ο b dynamics in the root zone. Soil samples were collected at multiple depths and horizontal positions over time during a maize growth period, and Ο b values were determined gravimetrically and indirectly from thermo-TDR measurements. Results showed that by using the extended de Vries model, the thermo-TDR measured Ο b agreed well with the gravimetric values. Ignoring root contribution to bulk soil heat capacity introduced 6.7%, 13.8% and 13.9% errors in thermo-TDR measured Ο b data on the loamy sand, sandy loam, and clay loam soils, respectively. A critical root density of 0.037 g cm β3 was determined beyond which roots may induce Ο b errors greater than 0.1 g cm β3 with the thermo-TDR technique.