Modification and validation of a LiDAR-based variable-rate airblast sprayer in lemon orchards (Citrus limon (L.) Osbeck)

Fruit production in Uruguay is characterized by a high degree of heterogeneity in species, training systems, and pruning management, which leads to marked variability in canopy volume, a key factor determining the efficiency of pesticide applications. However, conventional airblast sprayers do not adjust their application parameters in response to this variability. The objective of this study was to (i) evaluate different methods for estimating canopy volume, (ii) analyze application quality, and (iii) estimate water consumption for each system. Within the framework of the Innovagro 139485 project, a conventional airblast sprayer was modified by incorporating a LiDAR (Light Detection and Ranging) sensing system and the TRLV (Tree Row LiDAR Volume) canopy volume estimation model, which enables real-time adjustment of nozzle opening through PWM modulation according to the detected vegetation. The system was evaluated in a commercial lemon orchard, comparing a conventional application system (AC), based on the TRV (Tree Row Volume) method, with a variable rate application system (AVM) based on TRLV. Applications were carried out using Brilliant Blue tracer, and application quality was assessed at different canopy strata. In addition, the TRV, TRLV, and Ellipsoid methods were compared. The TRV method estimated the highest canopy volume values (15,664 m³ ha^-1), while TRLV (6,886 m³ ha^-1) and the Ellipsoid method (7,669 m³ ha^-1) showed similar results. Regarding application quality, the AC system achieved higher deposition levels (2.76 µg cm^-2) and coverage (62.36 %), whereas the AVM system showed lower values (1.10 µg cm^-2 and 33.65 %, respectively), although with a more uniform distribution. In terms of application rate, the AVM system achieved a 38.53 % reduction compared to the AC system. In conclusion, the variable rate application based on TRLV reduced the applied volume while maintaining a homogeneous and technically acceptable application, contributing to more sustainable crop management.