Development of alternative plant protection product application techniques in orchards, based on measurement sensing systems: A review

The development of alternative plant protection product (hereinafter PPP) application techniques in recent decades has been based on various principles of sprayer operation. So far, several researchers have tried with partial success to find a compromise (a uniform standard) to ensure continuous PPP application to selected tree canopies in an orchard. Researchers have offered certain solutions for controlling dosage rates of PPP, based on special measurement systems and decision-making models to optimize the dosage rate of PPP. With sensing systems for electronic canopy characterization, which originally functioned on the basis of ultrasound waving and later on the principle of spectral reflection, characteristics of tree canopies in an orchard could be adequately estimated. However, attention must be paid to the fact that discrepancies in the original measurement systems were too large, owing to imprecise operation of various sensor components. Nevertheless it is necessary to underline that advanced spectral laser technology is a strong tool for developers of alternative PPP application techniques, and with it, tree canopy properties are sensed in real time. So it is no longer a major problem in the precise application to establish the tree canopy properties, but to control artificial intelligence actuation, which in the future will properly direct the air flow and the dosage rate of PPP per tree canopy in the orchard.