High-speed imaging use to predict spray retention on barley leaves

in COMMUNICATIONS IN AGRICULTURAL AND APPLIED BIOLOGICAL SCIENCES (in press)

Laboratory studies were conducted to validate the effectiveness of the use of high-speed imaging method to replace chemical nalysis by fluoremetrie. Measurements were performed with a high-speed camera ... [more ▼]

Laboratory studies were conducted to validate the effectiveness of the use of high-speed imaging method to replace chemical nalysis by fluoremetrie. Measurements were performed with a high-speed camera coupled with a retro-LED lighting. Size and velocity of the drop were extracted by image analysis. Drop impact types were determined by the operator. Drops were produced with a flat-fan nozzle mounted on a movable ramp. Two surfactants (Break-Thru® S240 and Li700 ®) were sprayed on BBCH 12 barley leaves to highlight the effect of the reduction of surface tension. Relative volume proportions were computed within of an energy scale divided into 11 classes based on the Weber number. results are compared to the results of the chemical analysis by spectrofluerometry. [less ▲]

CHARACTERIZATION OF AGRICULTURAL SPRAY BY DIGITAL ANALYSIS OF SHADOWGRAPHY IMAGES

Poster (2013, February 08)

Agricultural sprays are among the most common two-phase flows studied because their characteristics determine the efficiency of treatment as well as environmental contamination. At present, the relevance ... [more ▼]

Agricultural sprays are among the most common two-phase flows studied because their characteristics determine the efficiency of treatment as well as environmental contamination. At present, the relevance of different characterization techniques of the highly polydispersed sprays used in this application remains controversial. Digital analysis of shadowgraphy images presents an attractive option for the characterization of both velocity and size of droplets present in the spray. This study presents an overview of the contrast problems inherent in the use of backlighted images and propose appropriate solution to ensure the quality of measurements. Generally, background light presents heterogeneities associated with light sources and optical arrangement. These can be solved by substracting from each images a composite background. An other particular focus is given to one major drawback of volumetric lighting, the presence of out focus droplets. These droplets have to be removed during the image analysis process because the measurement of their diameters can't be done accuratly. The rejection of these out of focus objects is based on a quantitative parameter which was calibrated with a obliquely shot monodispersed spray. The final step of the image processing is determining velocity of the droplet by tracking a same droplet on two successive images. The tracking algorithm is based on the size of the droplet, its more probable displacement and its direction. [less ▲]

Assessment of pesticide application method efficiency by high-speed image analysis

Conference (2012, July 08)

This paper investigates if increased blackgrass weeding efficiency by reduced volume per hectare observed during 2010 Arvalis field trials may be related to increased pesticide application method ... [more ▼]

This paper investigates if increased blackgrass weeding efficiency by reduced volume per hectare observed during 2010 Arvalis field trials may be related to increased pesticide application method efficiency. Retention on blackgrass leaves was assessed by an image analysis method. The setup consists of a high-speed camera shooting drop impact on horizontal leaf target. An herbicide (Archipel® [125 g/ha] + Actirob® [1 l/ha]) was sprayed at the usual volume of 150 l/ha and at a reduced volume of 65 l/ha. Adjuvants use (Epsotop® [1%] + Heliosol® [0.5%]) was also evaluated at 65 l/ha to highlight the effect of mixture surface tension modification. Drop properties before impact were extracted by image analysis and a phase diagram derived. Volumetric proportions of impact types are determined inside 11 energy classes to assess the effect of formulation and application method. The volume median diameter (VMD) before impact was slightly decreased by the reduction to 65 l/ha because of nozzle and pressure changes and also by the use of the adjuvants leading to the reduction of surface tension. Without adjuvants the reduction to 65l/ha increased the proportion of adhesion while rebound remained unchanged and fragmentation decreased. With adjuvants, drop fragmentation occurs for a lower energy class but the proportion of fragmentation also decreases with because of reduced VMD. A slight effect on the transitions between impact classes was observed because of formulation concentration change at reduced volume/hectare. A major effect of adjuvants on retention was highlighted as bouncing disappeared. [less ▲]

Experimental method for the assessment of agricultural spray retention based on high-speed imaging of drop impact on a synthetic superhydrophobic surface

in Biosystems Engineering (2012), 112(1), 56-64

Spray retention is a critical stage in pesticide application since non-retained drops can result in reduced efficacy, economic loss and environmental contamination. Current methods of retention assessment ... [more ▼]

Spray retention is a critical stage in pesticide application since non-retained drops can result in reduced efficacy, economic loss and environmental contamination. Current methods of retention assessment are based either on field experiments or laboratory studies. The former are usually performed on whole plants under realistic spray application conditions but offer no insight into the physics behind the process whilst the latter mainly focus on drop impact physics but are usually restricted to unrealistically low drop speeds. The aim of the paper is to devise an experimental method to investigate retention at drop scale level as a function of operational parameters but under controlled realistic conditions. A device based on highspeed video was developed to study retention on a synthetic superhydrophobic surface for a moving agricultural nozzle. The sizes and velocities of the drops generated were measured immediately before impact using image analysis. Impact class proportions were established and transition boundaries between impact outcomes were quantified using Weber number. Two contrasting experiments were performed to investigate the ability of method to detect small parametric changes. The insignificant changes in spray pattern that occur from pressure changes, did not significantly affect impact class boundaries, but changed the proportion of drops in each class because of size and velocity variations. The use of a surfactant reduced the volume median diameter of the spray, increased impact speed and changed the impact class boundaries. The method should allow a precise parametric investigation of spray retention in laboratory and close to field conditions. [less ▲]

Comparison of spray retention on synthetic superhydrophobic surface with retention on outdoor grown wheat leaves

in International Advances in Pesticide Application: Aspects of Applied Biology 114, 2012 (2012, January)

A method has been designed to test the retention of drops generated by a moving agricultural nozzle using high speed imaging both on synthetic and leaf surfaces. The method allows a precise investigation ... [more ▼]

A method has been designed to test the retention of drops generated by a moving agricultural nozzle using high speed imaging both on synthetic and leaf surfaces. The method allows a precise investigation of spray retention by a characterisation of impact speed, drop diameter and impact behaviour. The paper presents a comparison of the spray behaviour on the synthetic surface with the behaviour on outdoor grown wheat leaves fixed on a microscope slide. Target surfaces were horizontal. A range of surface tension was tested using the tank-mix adjuvant Break-Thru S240 at different concentrations in distilled water. Results show the relevance of a synthetic surface for use as reference for the assessment of spray application efficiency. The drop behaviour on the superhydrophobic slide was representative of difficult-to-wet leaves surfaces. The reference surface avoids the natural variability of leaves and is therefore more suited to conduct comparative assessment of formulation retention performance. [less ▲]