Assessment of Cotton Growth Using Ground-Based and UAV Remote Sensing

Simple and efficient measurement methods and devices are required to assess plant spatial and temporal variability for precision crop management. Cotton plant height and canopy spectral reflectance characteristics are important plant growth parameters. We measured cotton plant height and canopy reflectance using ground-based and UAV (Unmanned Aerial Vehicles) remote sensing methods in 2014 and 2015 season in a research field in Mississippi Delta. Experiments were conducted in cotton plots with substantially varied plant vegetation conditions. A ground-based plant health sensing system (PHSS), which equipped with ultrasonic sensor, multispectral sensor, and GPS receiver, was employed to scan the plant canopy for plant height and canopy reflectance in four visible wavebands. Meanwhile, RGB images of the cotton plots were acquired using an UAV-mounted camera, and processed for the plant height and canopy reflectance. Spectral reflectance measurements from the PHSS and UAV system were compared and used to calculate the plant NDPVR (Normalized Difference Photosynthetic Vigor Ratio). Sensor-measured plant height was compared with the manually measured plant height. Results indicate that the plant height estimated by the PHSS and UAV systems are strongly correlated with each other and with the manually measured height as well. These two remote sensing methods were able to be used for rapid assessment of cotton plant height and canopy spectral reflectance for precision crop management.