An Array for Measuring Detailed Soil Temperature Profiles

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.