UAS-Based Infrared Thermography for Evaluating Biofuel Crop Water Status.

Remote sensing of crop canopy temperature is a scientifically-based method to evaluate crop
water stress at or near real time. Potential approaches for estimating biofuel crop water
status from an unmanned aerial system (UAS’s) equipped with a thermal camera were evaluated in
this study. An experimental trial was set up in the central valley of Maui, Hawaii, comprising
four sugarcane and three energy cane varieties; four irrigation regimes with three
replications. Aerial thermal imagery of this field was acquired using a FLIR A615 thermal
camera mounted on the UAS’s. A weather station was installed in a full irrigation plot to
collect meteorological parameters. A method was developed to convert the temperature value of
each pixel into the crop water stress index. The results showed that low irrigation level
treatment plots resulted in higher canopy temperatures compared to the high irrigation level
treatment plots. Canopy temperatures in energy cane plots were lower than those in sugarcane
plots which may indicate that energy cane was less sensitive to water stress compared to
sugarcane varieties. The study shows that it is feasible to use a UAS’s thermal based method to
quantify plant water status of sugarcane or energy cane used for biofuel crops.