Nozzle choice for autumn weed control
Where the target is the soil, inclining the spray from both sides using a Twin spray or alternating nozzle spray direction will offer the best spray distribution especially where soil surfaces are uneven. Where good coverage is important the VPTech nozzle is the ideal choice , the finer droplet of the GuardianAIR Twin nozzle is an inclined option where drift reduction is the priority.
Looked at from above, even a high population of blackgrass plants does not present very much leaf area to receive spray droplets. A fine flat fan spray is essential for coverage and inclining the spray is also an advantage here.
Hypro's VPTech nozzle assembly is suitable for this target. It is important to follow label recommendations on water volume and use the correct pressure to achieve the spray quality that is required.
Research carried out by Silsoe Reasearch Institute (TAG) has shown that an inclined spray deposits 8% more spray onto metal rods chosen to represent 1 leaf blackgrass plants.
Field trials using an 03 flat fan VP nozzle with a forward incline have confirmed this.
The photo above shows blackgrass regrowth in the following crop of Linseed. Alternate boom widths were sprayed with the same product and water volume but through either a standard VP nozzle or one that was inclined at 40 degrees (Syngenta's Hawk nozzle). There is much less re-growth in the areas where the inclined nozzle was used, indicating that blackgrass control was much higher in these area - remember the only difference was the spray incline!
For latest industry advice on autumn spraying see also the FWI academy.