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An HGCA funded project investigating the minimum size of target, below which air inclusion nozzles may give inadequate biological control, when applying foliar acting herbicides to small weeds, such as black-grass has resulted in an important milestone in the understanding of air inclusion nozzles. Previously it had been considered that the larger the droplet size produced by air inclusion nozzles gave increased areas between droplet depositions thereby reducing the efficacy of foliar applied pesticides.
The results of a trial conducted over 2000/2001 seasons suggest that "comparable control of black grass" may be obtained with the BFS 02 Air Bubble Jet when compared to a conventional flat fan nozzle.
Figure 1 below, shows the percentage control of black-grass panicles that was achieved with Hawk plus oil at full and half recommended doses when applied at the 1 and 2-3 leaf stages of the black-grass.
In all cases the Air Bubble Jet 02 (Nozzle A) produced similar levels of control to the conventional flat fan (nozzle D) whilst the competing air-induction nozzles (B & C) achieved lower levels of control. This was particularly apparent at the lower doses of Hawk and/or when the target was small (i.e. 1 leaf).
The Air Bubble Jet performed better than competing air induction nozzles and in some cases this was significant. Even at the smallest (1 leaf) growth stage of black-grass, acceptable levels of control were achieved which were comparable to the conventional flat fan nozzle, although control by all nozzles tends to be better at the later timing when black-grass has 2-3 leaves.
All applications were undertaken with nozzles giving a nominal flow rate of 0.8 litres per minute at a pressure of 3.0 bars
Not all jets are created equal
Photographic spray pattern/deposition comparison of three Nozzles using water plus 0.1% of non-ionic surfactant.
NOZZLE SELECTION CHART
FOR CONVENTIONAL BOOM SPRAYERS TREATING CEREALS AND OIL SEED RAPE
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AIR INDUCTION NOZZLES |
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| LIKELY DRIFT POTENTIAL |
LOW |
| HERBICIDES (based on mode of action) |
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| SOIL ACTING |
++ # |
| FOLIAR ACTING |
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| Grass weeds 3 leaves or less |
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| Grass weeds more than 3 leaves |
+ # |
| Broad leaved weeds up to 2cm across |
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| Broad leaved weeds 2 - 5cm across |
+ # |
| Broad leaved weeds more than 5cm |
+ # |
| Non-selective (e.g. glyphosate) |
++ # |
| FUNGICIDES |
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| Cereals up to GS 23 |
+ # |
| Cereals up to GS 24-49 Rape vegetative stage |
++ # |
| Cereals over GS 50 (ear spray) Rape from green bud |
+ # |
| Cereals autumn spray Rape vegetative state |
+ # |
| Cereals ear spray Rape from green bud |
+ # |
KEY
Nozzle selections indicated are based on a normal application rate of 150 l/ha at forward speeds between 8 & 12 km/h and using a typical range of pressures for these nozzles
+ = Acceptable efficacy
++ = Preferred for efficacy
# = Highest level of drift control
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