Publication 360, Guide
to Fruit Production: Filling and Agitation
- Filling and Agitation
- Tank water
- Filling the tank
- Other Information on Pesticide Application
- Chapter 10, Pesticide
- Related Links
Filling and Agitation
- Mix pesticides with clean water that does not contain debris,
sand, mud or organic matter.
- Never let the water intake screen rest on a pond bottom when
filling a sprayer.
- The water intake line near the screen must, by law, have a check
valve or anti-backflow device. This prevents water-source contamination
when the pump is shut off.
- Do not use a tank-refilling nozzle, volume-booster nozzle, or
injection pump when refilling sprayer tanks from ponds or streams.
These tank-refilling aids may contaminate the water source.
- When using a farm water supply, install a frost-free water hydrant
outside the building. Place an anti-backflow valve or siphon prevention
on the discharge end of the hydrant.
- If required, adjust the pH or hardness of the water before mixing
spray materials in the tank. Where water is known to have an excessive
salt content, compatibility of the water and the chemical at field
strength should be tested first on a small scale.
Agricultural products are formulated to be as emulsifiable
as possible, but many do not mix well in water. They contain elements
that do not dissolve (e.g. wettable powders), or they may be petroleum
distillates (e.g. emulsifiable concentrates). Other products are
heavier than water and form precipitates (e.g. fertilizers and powdered
metals). Consequently, good agitation is very important.
Effective agitation requires water to "sweep"
the bottom of the tank so that any precipitated material is picked
up and re-mixed. Turbulence is not enough. If there is too little
agitation, the pesticide will be applied unevenly. If there is too
much agitation the pesticide may foam or cause an invert emulsion
(forming a gel).
There are two common types of agitation: mechanical
- Mechanical agitation is produced by paddles that are attached
to a shaft mounted near the bottom of the spray tank. While relatively
effective, this system cannot always sweep the very bottom of
the tank, so there is always some material that precipitates out
- Hydraulic agitation is accomplished by returning a portion of
the pump output to the tank. Cylindrical and oval tanks are the
ideal configuration for the rinsing (i.e. sparging) type of hydraulic
return agitation system. This system consists of a tube located
longitudinally along the wall of the tank, with volume booster
nozzles aimed at that centerline so they sweep across the bottom.
Volume booster nozzles take a small amount of water pumped into
their venturi chamber and create a vacuum that draws three to
four times that volume from the surrounding water and expels it
out the end. For hydraulic agitation to be effective, the agitator
nozzle(s) should be fed by a dedicated line from the pressure
side of the pump (not the pressure regulator). They should have
a valve to throttle the flow or completely shut it off to prevent
Filling the tank
Pesticide labels usually provide directions for mixing
different materials, including the sequence for mixing. Unless otherwise
specified (such as when using soluble pouches), follow the W.A.L.E.S.
method. In a half-full tank with agitator running, add:1.
- Wettable powders and flowables (including dissolvable
- Fill tank to ¾ full, agitate and then add
- Adjuvants such as anti-foaming compounds, buffers
- Liquid and soluble products
- Emulsifiable concentrates
Finish filling the spray tank to the required volume. Maintain
continuous agitation during mixing and final filling, and throughout
To prevent oil buildup in the sprayer, empty the tank completely
Clean the tank and sprayer with a detergent or solvent immediately
after use, then flush thoroughly with clean water.