Appraisal of a CDA rotary atomizer for weed control
Ouled Taleb Salah S., Massinon M. and Lebeau F.
Gembloux Agro-Bio Tech (University of Liege), Gembloux, Belgium
16
thEuropean Weed Research Society Symposium Samsun, Turkey
Appraisal of a CDA rotary atomizer for weed control
Ouled Taleb Salah S., Massinon M. and Lebeau F.
Gembloux Agro-Bio Tech (University of Liege), Gembloux, Belgium
16
thEuropean Weed Research Society Symposium Samsun, Turkey
Introduction
Crop protection is mainly achieved by spraying pesticides using hydraulic nozzles. This can lead to environmental contaminations that can be minimized with reduction of application rates. The challenge is therefore to ensure a required level of protection in these conditions.
Controlled Droplet Application (CDA) has proved to be the most successful way of delivering pesticides at very low volume application. In the past, their use was found inefficient in arable crops essentially due to bad settings, such as inappropriate application rate, and problem of penetration of spray in cereal canopies. These spray generators may be, however, the best solution when treating small hydrophobic weeds because spray retention can be maximized and drift of smaller droplets minimized thanks to reduced droplet span and increased VMD.
This study deals with blackgrass control in cereals while limiting environmental losses using properly set rotary atomizers. The droplet size and velocity were measured to characterize treatment efficiency.
Results and discussions
Rotary atomizers (Fig 2a) produce narrower droplet size distributions than hydraulic nozzles (Fig 2b and 2c) as it can be highlighted by a lower span defined by (DV90-DV10)/DV50 (Table 1). DV10, DV50 and DV90 indicates that 10, 50 and 90% of the volume of spray is in droplet diameters smaller
than this value.
Material and Methods
A high-speed camera used in double exposure mode coupled to a LED backlighting records water droplets produced by a Micromax® 120 (Micron) at various flow rates and rotating speeds (Fig 1). Images were analyzed with a Particle Tracking Velocimetry Sizing (PTVS) algorithm developed in Matlab®. This atomizer was benchmarked to a flat fan and an anti-drift nozzles for the same spray volume per hectare.
Conclusion and perspectives
PTVS allowed a good characterization of droplet size distributions required for the assessment of the application method efficiency. Reaching an optimal spray retention on weed surfaces while reducing the proportion of smaller droplets to reduce drift potential is a challenge that should rely on a reduced droplet span. Retention and drift are currently under investigation as a function of flow rate and rotating speed.
Flow rate
(ml/mn) DV10 (µm) DV50 (µm) DV90 (µm) Span (DV90-DV10)/DV50
Micromax (5000 rpm) 560 181 271 347 0.60
Teejet XR 11002 560 113 208 361 1.18
Hardi Injet 015 560 177 325 514 1.03
Fig 3. Drop formation for a rotary atomizer
Despite of the uniformity of CDA sprayer size distribution, satelite droplets were observed due to a natural spray desintegration (Fig 3). This phenomenon is gradually reduced when rotation speed is rised.
Fig 2. Droplet size distribution for the same applied volume: (a) Micromax (5000 rpm, 560 ml/mn), (b) Teejet (560 ml/mn), (c) Hardi 015 (560 ml/mn)
Micromax Teejet XR11002 Hardi 015
Vol 100 (%) 0.70 6 0.99
Vol 350 (%) 8 11 41
Table 1. Characteristics of the spray
Table 2. Volume percentage of spray droplets
Generally satelite droplets are prone to drift and coarse droplets that exceed 350 µm have a tendency to splash at impact on leaves. Rotary atomizers emit theorically a low percentage of droplets under 100 µm and above 350 compared to a flat fan and anti-drift nozzle for the same volume per hectare (93 l/ha) (Table 2). Vol 100 and Vol 350 represent the percentage of droplets whose diameters are under 100µm and above 350 µm in the spray volume. 0 100 200 300 400 500 600 0 10 20 R el at iv e vo lu m e[ % ] Diameter [µm] 0 100 200 300 400 500 6000 50 100 R el at iv e cu m ul at iv e vo lu m e [% ] 0 100 200 300 400 500 600 0 5 10 R el at iv e vo lu m e [ % ] Diameter [µm] 0 100 200 300 400 500 6000 50 100 R el at iv e cu m ul at iv e vo lu m e [ % ]
a
b
c
LED
micromax
camera
Fig 1. Experimental device
0 100 200 300 400 500 600 0 2 4 6 8 10 R el at iv e vo lu m e [% ] Diameter [µm] 0 100 200 300 400 500 6000 20 40 60 80 100 R el at iv e cu m ul at iv e vo lu m e [% ]
