An array for measuring detailed soil temperature profiles

Authors: Wuest, Stewart

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2012
Publication Date: 1/18/2013
Citation: Wuest, S.B. 2013. An array for measuring detailed soil temperature profiles. Soil Science Society of America Journal. 77(2):427-431.

Interpretive Summary: Soil temperature dynamics in surface soil can be used to measure changes in heat and water flow, which are important in understanding evaporation from the seed zone in semi-arid cropping systems. We designed an easy to install array of electronic thermometers for routine measurement of detailed surface soil temperature profiles. We tested the array for accuracy, and found that under certain conditions it reads very close to the true surface temperature, but up to several degrees warmer than the soil at 1 to 4 cm below the surface. Deeper temperatures were more accurate, and tests under normal field conditions demonstrated that the array can produce realistic temperature profiles.

Technical Abstract: Soil temperature dynamics can provide insights into soil variables which are much more difficult or impossible to measure. We designed an array to measure temperature at precise depth increments. Data was collected to determine if the construction materials influence surface and near-surface temperature estimates during peak insolation. In dry sand, arrays disagreed with a bare reference thermistor at the soil surface by -6 to +5 °C, averaging +0.42 °C. At depths of 1 to 4 cm, the arrays averaged from 3 down to 1 °C warmer during a sunny day, indicating that construction material was conducting heat from the surface at a greater rate than the sand. The average difference between arrays and a reference at 13-cm depth in sand was -0.30 °C (standard deviation = 0.42). Under field conditions in a dry silt loam, the arrays did not show the near-surface daytime bias, and agreed within 1 °C of independent measurements at 2 and 5 cm. The array facilitates multiple measurements of detailed temperature profiles. These measurements are capable of detecting the effect of soil conditions such as tillage, layering, or water content on the flow of heat at a resolution of centimeters.