The first season of field trials in citrus orchards
Two experiments were performed to evaluate the differences between conventional and optimized applications, in terms of, on one hand, off-target losses, which include ground losses and spray drift, and on the other hand, dermal exposure of operators and bystanders. Conventional applications were based on the standard applications following indications from the farm technicians. Optimized applications were based on the use of CitrusVol OVRA tool to calculate the volume rate, and low-drift nozzles as an SDRT, together with the selection of other operational parameters following Good Agricultural Practices (forward speed, working pressure, number of active nozzles, nozzles size, airflow rate, and deflector position).
Furthermore, evaluations were performed both directly, by measuring the pesticide and its metabolites in the air, and the urine of operators and volunteers acting like bystanders; and indirectly, by measuring the pesticide deposition with artificial collectors placed in different study compartments (ground, air, operators and bystanders). Direct evaluations allow real measurement in the intended substrate, but they need specialized and expensive equipment and give very low resolution in the space. Instead, indirect evaluations allow higher resolution, do not require specialized equipment and need cheaper materials. The final goal was also to evaluate the relationship between direct and indirect measurements and validate the latter ones.
The experimental farm, Masia El Palmeral (part of Villa Res S.A. farms), is located at El Puig (Valencia province, Spain) (39◦36’33.3’’N; 0◦21’13.8’’W), an area with a typical Mediterranean climate. The farm has an extended and scattered set of citrus orchards. Two of them were used in the trials, one for exposure assessments (Figure 1), and another one for off-target losses assessments (Figure 2). To avoid cross-contamination between treatments of air samplers, operators and bystanders, the application of each treatment was performed on a different day with similar climatic conditions, and early in the morning to avoid high wind speeds.
In the following figures the equipment/materials used for the direct evaluations (A), and the indirect evaluations (B), and the applications themselves (C), are shown:
A) Direct evaluation:
B) Indirect evaluation: