References of "Boukhalfa, Hassina dite Hafida"
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See detailContribution of Spray Droplet Pinning Fragmentation to Canopy Retention
Boukhalfa, Hassina dite Hafida ULg; Massinon, Mathieu ULg; Belhamra, Mohamed et al

in Crop Protection (2014), 56

Drop behaviour during impact affects retention. The increase of adhesion is usually seen as the objective when applying crop protection products, while bouncing and shattering are seen as detrimental to ... [more ▼]

Drop behaviour during impact affects retention. The increase of adhesion is usually seen as the objective when applying crop protection products, while bouncing and shattering are seen as detrimental to spray retention. However, observation of drop impacts on barley (Hordeum vulgare L.) using high speed shadowgraphy shows that bouncing and fragmentation can occur in Cassie-Baxter as well as in Wenzel wetting regimes. In this last regime, a part of the drop may remain stuck on the surface, contributing to retention. Using simultaneous measurements of drop impacts with high speed imaging and of retention with fluorophotometry for spray mixtures on excised barley leaves using a Teejet 11003 nozzle at 0.2 MPa, it is observed that about 50% of the drops that fragmented in the Wenzel state remain on the horizontal leaf. Depending on the spray mixture, these impact outcomes accounted for 28 to 46% of retention, the higher contribution being correlated with bigger VMD (Volume Median Diameter). This contribution is not negligible and should be considered when modelling spray retention processes. [less ▲]

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See detailSpray retention assment combining high-speed shadow imagery and fluorescence techniques
Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg; Lebeau, Frédéric ULg

in International Advances in Pesticide Application: Aspects of Applied Biology 122, 2014 (2014, January 08)

Droplet behaviour during impact affects retention by leaves. The increase of droplet adhesion to plant leaves is the objective when applying crop protection products, while droplet bouncing and ... [more ▼]

Droplet behaviour during impact affects retention by leaves. The increase of droplet adhesion to plant leaves is the objective when applying crop protection products, while droplet bouncing and fragmentation are usually seen as detrimental to spray retention. However, observation of droplet impacts on barley using high speed imaging showed that fragmentation impact outcome can occur in two different wetting regimes: Cassie-Baxter or Wenzel’s regime. In the latter, a fraction of the droplet is anchored in the surface roughness, what contributes to retention. Three mixtures were sprayed on excised barley leaves with an 11003 flat-fan nozzle operating at 0.2 MPa. Simultaneous measurements were performed using high speed imaging for droplet impact characterisation. A fluorescent tracer was added to the spray mixture for retention assessment. Retention was related to impact type considering the fraction of the droplet remaining on the leaf surface after a droplet splashing occurring in Wenzel’s wetting regime. This fraction varied from 28‒46% depending on the spray mixture and was correlated to the Volume Median Diameter DV0.5 of the impacting droplets. [less ▲]

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See detailThe effect of surface orientation on spray retention
Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg; Lebeau, Frédéric ULg

in Precision Agriculture (2014)

Research in precision spraying investigates the means to reduce the amount of herbicide applied by directing droplets more accurately towards the weeds. The trend in the development of spot spraying ... [more ▼]

Research in precision spraying investigates the means to reduce the amount of herbicide applied by directing droplets more accurately towards the weeds. The trend in the development of spot spraying equipment is an increase of the spatial resolution and new actuators that are able to target very small areas. However, there is a lack of methods for assigning rates of herbicides relating target to optimal droplet features. A wide range of droplet impact angles occurs during the spray application process because of droplet trajectories and the variability of leaf orientation. In this study, laboratory experiments were conducted to highlight the effect of surface orientation on droplet impact outcomes (adhesion, rebound or splashing) on two very difficult-to-wet surfaces: an artificial surface with a regular roughness pattern and an excised black-grass leaf with an anisotropic roughness pattern. Measurements were performed for different surface orientations with a high-speed camera coupled with backlighting LED. Droplets of two formulations (distilled water and distilled water + a surfactant) were produced with a moving flat-fan hydraulic nozzle to obtain a wide range of droplet sizes and velocities, which were measured by image analysis. Increasing surface angle reduces surface area available for droplet capture. Droplet impact behaviors are then modified since surface tilt induces a tangential velocity component at impact and, consequently, a reduction of the normal component. Impact modifications have also been observed due to the anisotropic roughness pattern of a black-grass leaf. The integration of droplet-surface interaction information offers a significant way to further improve the precision spraying efficiency by considering the optimal droplet size, speed and ejection angle depending on the target surface and architecture. [less ▲]

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See detailUse of rotary atomiser to optimize retention on barley leaves while reducing driftable droplets
Ouled Taleb Salah, Sofiene ULg; Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg et al

in International Advances in Pesticide Application, Aspects of Applied Biology 122 (2014, January)

Controlled Droplet Application using rotary atomiser is based on an improved control of droplet size and trajectory comparatively to hydraulic nozzles. On the basis of literature, it was stated that the ... [more ▼]

Controlled Droplet Application using rotary atomiser is based on an improved control of droplet size and trajectory comparatively to hydraulic nozzles. On the basis of literature, it was stated that the use of 60° forward angled spray combined with the narrow drop size distribution of a rotary atomiser could lead to low drift and high retention on monocotyledonous and superhydrophobic weeds at early stage. A Micromax120 atomiser was tuned to emit 270 µm VMD, 60° angled forward, to increase interception by the canopy structure. A spray mixture containing a superspreader adjuvant was used to avoid drop bouncing. An increase of spray retention comparatively to a Teejet 11002 at 1.4 bars was observed, although not proved statistically significant by these preliminary trials. On the drift side, the tilted spinning disc seemed to be advantageous since droplet spectra contains a low percentage of droplets under 100 µm and presents an ejection velocity of 25 m.s-1 at 5000 RPM. The spray drift was reduced about 50%. However, these setting were not found as efficient as expected. Indeed, angled spray proved to be more sensitive to advection and turbulence, as the spray was more exposed to the airflow than for the vertical position. It appears that angling the spray and choosing a drop size spectrum with a Volume Median Diameter as big as 270 µm is not sufficient to reduce significantly this issue. Some alternatives as decreasing the emission height are possible with angled sprays but require height control that seems difficult to reach in practical situations. [less ▲]

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See detailHigh-speed imaging use to predict spray retention on barley leaves
Boukhalfa, Hassina dite Hafida ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

in Communications in Agricultural and Applied Biological Sciences (2013, May 21), Vol 78(2)(1-386 (2013)), 31-36

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 ▲]

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See detailImprovement of spray retention on barley leaves by adjuvants
Boukhalfa, Hassina dite Hafida ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2013, April 18)

Adjuvants contribute to change the types of impact and thus the amount of spray retained by the leaves of the treated plant. We have performed tests of retention on barley plants on BBCH 12 stage and ... [more ▼]

Adjuvants contribute to change the types of impact and thus the amount of spray retained by the leaves of the treated plant. We have performed tests of retention on barley plants on BBCH 12 stage and small pieces of barley leaves at the same stage of growth. Spraying was done in three ways: water without adjuvant, water with Break-Thru® S240 and water with Li700®. The three slurries of fluorescein contained in an amount of 0.2 g / l. Fluorescein retained by the leaves in both cases is then measured by a spectrofluoremeter. The retention tests on whole plants show that it is tripled by the first adjuvant and doubled by the second. On the other side, on small pieces of barley leaves, the amount was increased by the use of surfactants but not to the same extend. This study concluded that the use of adjuvants in spray pesticides increases the amount of retention as a function of leaf area and the type of adjuvant. [less ▲]

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See detailSTUDY OF THE EFFECT OF TWO SURFACTANTS ON SPRAY RETENTION BY BARLEY LEAVES
Boukhalfa, Hassina dite Hafida ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Poster (2013, February 08)

Surfactants are nowadays very useful additives to improve the effectiveness of phytosanitary treatments. They contribute to change the types of impact and thus the amount of spray retained by the leaves ... [more ▼]

Surfactants are nowadays very useful additives to improve the effectiveness of phytosanitary treatments. They contribute to change the types of impact and thus the amount of spray retained by the leaves of the treated plant. We performed tests of retention on whole barley plants on BBCH 12 stage and small pieces of barley leaves at the same stage of growth. Spraying was done in three ways: water without surfactant, water with Break-Thru S240 and water with Li700. The three slurries of fluorescein contained in an amount of 0.2 g / l. Fluorescein retained by the leaves in both cases is then measured by a spectrofluoremeter. The retention tests on whole plants show that it is tripled by the first surfactant and doubled by the second. By cons on small pieces of barley leaves, the amount was increased by the use of surfactants but not to the same scale. This study concluded that the use of surfactants in spray pesticides may increase the amount of retention as a function of leaf area and the surfactant used. [less ▲]

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See detailTHE EFFECT OF LEAF ORIENTATION ON SPRAY RETENTION ON BLACKGRASS
Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg; MARECHAL, Pierre- et al

Conference (2012, July)

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop ... [more ▼]

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop trajectory and the variability of the leaf orientation. As the effect of impact angle on retention is still poorly documented, laboratory studies were conducted to highlight the effect of leaf orientation on drop impact outcomes. 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. Excised blackgrass [Alopecurus myosuroides HUDS. (ALOMY)] leaves were stretched between two parts of a U-shaped support. A surfactant (Break-Thru® S240) was sprayed to highlight the effect of mixture surface tension. The whole device was tilted from 0 to 90°. Relative volume proportions were computed within of an energy scale divided into 11 classes. These proportions have been weighted by an average volume distribution and the results were summed for all energy classes to obtain the total volume proportions for each impact outcomes and for all leaf angles. For distilled water (high surface tension) the increase of rebound proportion with the increase of drop impact angle is highlighted. For surfactant (lower surface tension), it results in an increase of drop fragmentation in Cassie-Baxter wetting regime. To be statistically representative, bigger drop samples should be used. [less ▲]

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See detailRISQUES DE POLLUTION LIES À LA PULVERISATION DES PESTICIDES
Boukhalfa, Hassina dite Hafida ULg

Poster (2012, February 03)

L'étude de la dispersion des pesticides est fondamentale pour diminuer les pollutions environnementales mais elle s'avère particulièrement complexe. L’application de pesticides consiste généralement en la ... [more ▼]

L'étude de la dispersion des pesticides est fondamentale pour diminuer les pollutions environnementales mais elle s'avère particulièrement complexe. L’application de pesticides consiste généralement en la pulvérisation d’une bouillie liquide constituée d’eau, de matière active et d’adjuvants. La taille et la vitesse initiales des gouttes produites en sortie de buse conditionnent fortement le transport (hors cible: dérive: pollution de l’air) ainsi que le dépôt de ces gouttes (hors cible: pollution de l’eau et des sols). La pollution de l'air par les pesticides est l'un des grands problèmes environnementaux aux quels est confrontée l'agriculture, et la réversibilité de ses effets sur l'environnement et la santé est encore peu connue. Lors des traitements phytosanitaires, une partie relativement importante des produits pulvérisés est perdue dans l'environnement. La toxicité des pesticides est reconnue mais, au contraire des niveaux mesurés dans les eaux destinées à l'alimentation en eau potable, les teneurs en pesticides dans l'air ambiant ne sont pas actuellement normés ou réglementés. Les risques pour la santé dépendent de la toxicité des matières actives et de leurs concentrations dans les milieux d'exposition (air, eau, aliments). Dans le but de pouvoir estimer les risque de pollution de l'air par les pesticides nous avons étudié l'influence de quelque paramètres sur la répartition des jets de pulvérisation issus d'un pulvérisateur à pression de liquide à jet projeté, à savoir: la pression, la vitesse du vent, la hauteur des buses et le type de buse. Les résultats obtenus on permit de mettre en évidence la contribution du réglage du matériel de pulvérisation en la quantité de pertes en produit pulvérisé et d'en déduire approximativement le risque de pollution environnementale. [less ▲]

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See detailEffets de la variation de pression sur la qualité des jets de pulvérisation et leur contribution aux risques de pollution environnementale.
Boukhalfa, Hassina dite Hafida ULg

Conference (2011, November 16)

Un traitement phytosanitaire s’effectue en visant un triple objectif: être efficace, ne pas mettre en danger l’opérateur et protéger l’environnement. (MOREAU et al., 1997). La quantité de pesticides ... [more ▼]

Un traitement phytosanitaire s’effectue en visant un triple objectif: être efficace, ne pas mettre en danger l’opérateur et protéger l’environnement. (MOREAU et al., 1997). La quantité de pesticides appliquée chaque année est estimée à 2.5 millions de tonnes mais la part de cette quantité qui entre en contact avec les organismes indésirables est très faible. La plupart des chercheurs l’évaluent à moins de 1% (ELAISSAOUI et al., 2004), ce qui veut dire que 99% des substances chimiques entre en contact avec le milieu environnant d’une manière non ciblé et sont potentiellement dangereux pour les écosystèmes entiers. D'après FAGOT et LARRAT (2002), la pression a un effet direct sur la répartition du produit et le volume de bouillie appliqué par son action sur la taille des gouttelettes et sur l'angle du jet de pulvérisation. Dans le but d’accroître l’efficacité de pulvérisation de pesticides et de réduire les pertes diverses de bouillie qui en résultent, nous avons étudie l’influence de la variation de pression sur la forme et la composition d’un jet de pulvérisation à l’aide d’un pulvérisateur à pression de liquide à jet projeté avec une buse à turbulence. Le travail a été effectue avec 5 valeurs de pression 0.5 bar, 1 bar, 1.5 bar, 2 bar et 2.5 bar. Les résultats obtenus nous ont permit d'en déduire que la pression de 1bar donne la meilleure couverture et répartition du jet de pulvérisation. A partir de la pression de 1.5 bar commence la dérive, et des pressions plus élevées rendent le jet irrégulier et hors cible. L'augmentation de pression augmente les pertes en bouillie et la quantité de fines gouttelettes. [less ▲]

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