MIXING OF HERBICIDES

Mixing Herbicides before Application-Warning

Be aware that improper sprayer calibration, calculation errors, or use of the wrong chemicals can cause herbicide injury to the crop.

Mix only the recommended amount of herbicide.

Slight increases in rates could result in crop injury or leave residues that might injure succeeding crops.

Recalibrate sprayers frequently and adjust them for increased output resulting from normal nozzle wear

Be sure there is sufficient agitation in the sprayer tank to prevent settling of wettable powders, dry flowables, or flowables.

STEPS WHEN MIXING

Read the label

Calculate the amount

of herbicide needed. Fill the sprayer tank

at least halfway.

Add, mix, and disperse dry formulations (wettable powders, dry flowables, or water-dispersible granules).

Mixing Order. Herbicide labels usually provide directions for mixing

different materials, often describing the sequence of

mixing.  Whenever a label provides such directions, you

should follow them. In general, follow the W-A-L-E-S plan

when adding herbicides to a tank mix.

1.  Wettable Powders (WP) then Flowables (F, DF)

2.  Agitate then add adjuvants such as anti-foaming

compounds, buffers

3.  Liquid and Soluble products 4.  Emulsifiable concentrates (EC)

5.  Surfactants        

 Pre-mixing the following: Wettable powders (WP).  Dry flowable (DF) and water-dispersing granules (WDG), Liquid flowables (Ratio=1:2)

                                                                                                             

MIXING STEPS-Contd. Add the remainder of water and agitate.

Caution: Never pour concentrated herbicides into a empty tank. Never allow a sprayer

containing mixed chemicals to stand without agitation, as heavy wettable powders may

clog nozzles or settle into corners of the sprayer tank

Test pH Many incompatibilities result from excessively alkaline (sometimes acidic) pH in

the tank. The addition of buffering adjuvants can help.

Make a test application to expose any phytotoxicity or antagonism before you make a

large-scale application.  If you overlap a few strips, this also can show you how much of a

margin of safety you have. Wait a few days for symptoms to become visible. Do not mix iron sulphate with phenoxy herbicides.  Iron sulphate is

incompatible with amine formulations of some phenoxy herbicides and can cause a precipitate to form, clogging spray equipment.

Mix no more than one soluble or emulsifiable chemical with any insoluble products such as wettable powders or flowables.

Mix no more than one soluble or emulsifiable chemical with any insoluble products such as wettable powders or flowables.

Avoid mixing strongly acid materials with strongly alkaline materials

Apply sprays soon after mixing.  Mixes that sit for several hours or longer are prone to degrade, especially if the pH is alkaline.

Often EC formulation and WP formulations result in

phytotoxicity. This is often due to the solvents,

carriers, emulsifiers.

Do not mix granular formulations with liquids

MIXING STEPS-Contd.

Reduced effectiveness of one or both compounds

Precipitate in the tank, clogging screens and nozzles in the sprayer.

Plant phytotoxicity, stunting or reducing seed germination

Excessive residues

Excessive runoff

Effects of mixing incompatible herbicides may include

Applicator Safety Tips When Mixing Products

When handling herbicides on-site, always follow PPE precautions and keep in mind the importance of safety before making the mixtures.

Be aware of all mixing requirements and procedures indicated on the product labels.

Keep containers below eye level

when opening and pouring.

Keep fill hoses above water

level in the spray tank to

prevent back-siphoning.

Be aware of wind direction

before pouring to minimize

exposure downwind.

TABLE: 1. HERBICIDE DILUTION & EQUIVALENTS( RATE= 6L/HA)

SPRAYER CAPACITY

HERB. MLS/LOAD

MILK-TIN MEASURE

TOMATO-TIN MEASURE

REMARK

5L 150ml 1 2 ¼ CP 5

10L 300ml 1 ¾-2 4-4 ½ 10L

15L 450ml 2 ¾ 6 ½ CP 15

20L 600ml 3 ½ 8 ¾-9 CP3, JACTO