Assessment of Drone Agricultural Spraying Operations Using Optical Fiber Sensors

Drone spraying operations are increasingly integrated into agricultural practices and play a crucial role in Precision Agriculture. However, their broader adoption is still limited due to concerns related to droplet drift effects. Herein, an optical fiber sensing probe based on a long period grating is employed for monitoring droplet dispersion during drone spraying operations. Τhe sprayed micro-droplets dissipate onto the exposed cladding area of the long period grating, introducing amplitude changes and wavelength shifts of the characteristic attenuation spectral notch. Open field trials, over a tarmac area, and an olive tree orchard have been performed to obtain realistic implementation data while correlating the spectral changes obtained from the optical fiber probes with droplet coverage area figures measured with conventional methods. Normalised amplitude changes of up to 17% have been registered for the transmission notch of long period grating sensors when exposed to droplet coverage areas of ∼5.9%, for open field spraying. Furthermore, the operation of the sensor was confirmed for distances up to 22 m away from the drone spraying path in olive tree orchard. Preliminary investigations indicate that a spraying volume per area of 0.07 ml/100 cm² detected through droplet dissipation of the optical fiber sensor during drone spraying operations in an olive tree orchard, is adequate for tracing common pesticide active ingredients used in pest management, well below their Wipe Limit figure.