Francesc Solanelles

Airborne spray drift measurement using passive collectors and lidar Systems

Minimization of the risk associated with spray applications requires a proper understanding of the spray drift phenomenon. This fact has led to the development of several techniques to measure the deposition on horizontal surfaces as well as the airborne spray profiles. Assessment of airborne spray drift is particularly difficult because this phenomenon is subject to variable micrometeorological conditions. However the monitoring of airborne drift has a great importance since it can be carried over long distances. This paper reviews main sampling techniques currently used to asses the airborne spray drift, based on passive collectors and tracers. Theoretical principles that determine the efficiency of passive samplers are studied as well as the performance of different types of tracers. On the other hand, this paper shows new airborne spray drift assessment techniques based on lidar technology, reviewing its principle of operation as well as its practical application in several spray drift trials. It is concluded that the lidar technique has significant advantages over conventional methods, especially in terms of time consumption and monitoring capabilities. However, the future adoption of lidar technology for airborne spray drift studies will be subjected to the development of lidar instruments really adapted to this application.

Advances in pesticide dose adjustment in tree crops

Recently, there have been several attempts to introduce new pesticide dosing methods for fruit orchards and vineyards. However, in Southern Europe, these new methods have not been adopted. This is mainly because farmers lack confidence in the new methods. This lack of confidence partly results from the failure of the new dosing methods to take into account tree leaf density. For this reason, the most common dosing method is the traditional one which is used to control the concentration of the pesticide solution to be sprayed. In this context, farmers tend to spray a greater volume than is necessary and therefore frequently overdose their orchards. A method for estimating the Leaf Area Index was developed. This methodology was then implemented in a decision support system and validated over four seasons, 2009-2012. The decision support system allowed significant reduction in the volume of pesticide sprayed while maintaining the same level of biological efficacy. This system could provide the basis of a universal dose method for pesticide spraying in tree crops.

Measurement of Spray Drift with a Specifically Designed Lidar System.

Field measurements of spray drift are usually carried out by passive collectors and tracers. However, these methods are labour- and time-intensive and only provide point- and time-integrated measurements. Unlike these methods, the light detection and ranging (lidar) technique allows real-time measurements, obtaining information with temporal and spatial resolution. Recently, the authors have developed the first eye-safe lidar system specifically designed for spray drift monitoring. This prototype is based on a 1534 nm erbium-doped glass laser and an 80 mm diameter telescope, has scanning capability, and is easily transportable. This paper presents the results of the first experimental campaign carried out with this instrument. High coefficients of determination (R2 > 0.85) were observed by comparing lidar measurements of the spray drift with those obtained by horizontal collectors. Furthermore, the lidar system allowed an assessment of the drift reduction potential (DRP) when comparing low-drift nozzles with standard ones, resulting in a DRP of 57% (preliminary result) for the tested nozzles. The lidar system was also used for monitoring the evolution of the spray flux over the canopy and to generate 2-D images of these plumes. The developed instrument is an advantageous alternative to passive collectors and opens the possibility of new methods for field measurement of spray drift.

Spray application volume test in apple and pear orchards in Catalonia (Spain) and Variable Rate Technology for dose adjustment.

The adjustment of spray application conditions is still an issue in spray applications in fruit crops. Many fruit varieties are found in apple and pear orchards, that can be in different development stages and grown in a wide range of training systems. The active ingredient of a pesticide preparation can be delivered using different volume application rates (VAR), which if not well adjusted to each orchard can cause a diminution of the application efficiency. The objective of the work was to decide the best VAR in two apple varieties (Golden and Red Chief) and two pear varieties (Blanquilla and Conference). During two growing seasons, three VAR (400, 800 and 1600 l/ha) were tested in different orchards. Spraying parameters were kept as similar as possible (sprayer, forward speed, droplet size, air volume rate, weather conditions, etc.) so that the differences were mainly caused by the tested VAR. Depending on the results, there was a possibility to design and test a variable rate (VR) sprayer prototype able to deliver an specific flow rate according to the volume of vegetation detected by ultrasonic sensors. According to the results, no clear trends were found between the three different VAR, although it seems that the lowest VAR could be more suitable for early season spraying, whereas in full stage applications the highest VAR seemed more adequate. The fact that the same droplet size and a last generation sprayer were always used can explain why no differences between the corresponding spray deposits were found. The results found led us to develop and validate the VR prototype turning out into very optimistic results on dose adjustment in real-time.

Polarization lidar detection of agricultural aerosol emissions

Agricultural aerosol emissions can significantly impact human and animal health as well as the environment. Therefore, it is essential to adopt new sensing techniques for real-time monitoring these emissions in high temporal and spatial resolution. In recent years, light detection and ranging (lidar) technology has been used for measuring the particulate matter emitted from agricultural operations. However, conventional nonpolarized lidar systems cannot discriminate between different types of aerosols, which can lead to misinterpretation of the results. To overcome this limitation, this study applies the polarization lidar technique to monitor agricultural aerosols. A 355 nm polarization lidar system was used to measure the emissions generated during pesticide spraying operations. The results showed that depolarization ratios due to field dust (0.220–0.268) and to road dust (0.385) are clearly higher than those caused by pesticide spray drift (0.028–0.043) or by diesel exhaust (0.099), which can be used to differentiate each type of aerosol. These results support the development of new polarization lidar systems specifically designed to study the impact of agricultural activities on air quality.