High-Throughput Phenotyping of Wheat Canopy Height Using Ultrawideband Radar: First Results

This letter presents an experimental study on the use of ultrawideband (UWB) probing radar as a new type of sensor to efficiently and nondestructively measure plant structure for breeding applications, focusing here on wheat canopy height. Wheat canopy height is an important morphological and developmental phenotype that indicates plant growth and it is related to biomass. Currently, taking manual measurements of canopy height is labor-intensive and has become a bottleneck for genomic selection and breeding programs. Other recently proposed noncontact methods only sense the top of the canopy, thereby having to make assumptions about the elevation of the base of the canopy. We propose the use of UWB radar as a phenotyping sensor for measuring a variety of plant characteristics. A direct measurement of wheat canopy height is investigated with the capability of sensing both the top and the bottom of the canopy simultaneously. To test this idea, we developed a 2-18-GHz frequency-modulated-continuous-wave (FMCW) radar prototype and a mobile phenotyping platform. The sensor was tested by collecting near-nadir coherent radar measurements of wheat canopies of breeding plots at different growth stages. The performance to detect both the top and bottom of the canopy was examined at different frequency bands.