Herbicide Usage and Calculations

Herbicide carriers

Are some inert materials mixed with herbicides for uniform spreading. eg., sand, water, dry soil, clay etc.

Water requirement for spray solution

For uniform application over a large area requires mixing of the herbicide with required quantity of carrier needed. The amount of water used affects the herbicide’s effectiveness and the ease of application.
The quantity of water required for spraying a given area =
area to be sprayed in m2 x sprayer output in lit/ha
       10,000

Herbicide formulations and calculations

Commercial solid formulations

concentration is expressed as percentage of the weight of the active ingredient by the weight of commercial solid herbicide (weight/weight).

Soluble concentrates(SC)

The active ingredient dissolves readily in water. They are cheaper than wettable powders

Commercial liquid formulations

(EC- concentration is expressed as the weight of the active ingredient by the volume of the commercial emulsifiable concentrate herbicide (weight/ volume). Different herbicide formulations are given below.

Flowables (F)

The active ingredient is not readily soluble in water or organic solvent. But it is finely ground wettable powder suspended in a small amount of liquid and mixed with emulsifiers.

Emulsifiable Concentrate

This is not water soluble but soluble in organic solvents. To form a stable oil-in water emulsion when the herbicide is mixed with water, an emulsifier is added.

Granules (G)

The dry ingredient with a carrier is ready-to-use formulation and contains 2-20% active ingredient. Granular herbicide handling and application is easy but bulky and handling cost is high.

Wettable Powder (WP)

Wettable powders mix readily with water but tend to settle at the bottom of the spray tank. It is made of dry active ingredient and inert solid like clay along with dispersion agents. This is made only when active ingredient does not dissolve in standard solvents.

Adjuvants

Materials that facilitate or modify the characteristics of herbicide formulation. eg. Surfactants, wetting agents, oils, stickers, thickening agents, emulsifiers and stabilizing agents.
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