Infrared thermometry to quantify in-field soil moisture variability

Techniques to formulate accurate and timely prescriptions for variable-rate irrigation systems lag behind the hardware capabilities. Canopy temperature measurements could serve as an indicator of water stress, but current methods that exploit the data can be cumbersome. The objectives of this study were 1) to determine the relationship between synchronous measurements of maize (Zea mays L.) canopy temperature and in-field soil moisture tension, and 2) to understand the influence of discretionary crop canopy temperature stress thresholds on the relationship between soil moisture tension and crop canopy temperature. A variable-rate irrigation pivot was used to form six water-treatment zones. Each zone was equipped with tensiometers installed in the center of the plots and an infrared thermometer pointed into the crop canopy to individually monitor conditions in each zone. Results of this study indicate that synchronous canopy temperature was able to quantify soil moisture tension, particularly during the reproductive crop growth stages. Using inexpensive infrared thermometers with this method could provide a cost-effective solution for gauging in-field soil moisture variability.