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AGR 3102 Principles of Weed Science Herbicide


AGR 3102 Principles of Weed Science Herbicide Muhammad Saiful Ahmad Hamdani Unit 6 Topics Covered Herbicide Calculations: a.i. (active ingredients) a.e. (acid ... – PowerPoint PPT presentation

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Title: AGR 3102 Principles of Weed Science Herbicide

AGR 3102Principles of Weed ScienceHerbicide
  • Muhammad Saiful Ahmad Hamdani

Unit 6 Topics Covered
  • Herbicide Calculations
  • a.i. (active ingredients)
  • a.e. (acid equivalent)
  • Calibration

Herbicide Calculations
  • 2 methods
  • 1) active ingredients (a.i.)
  • 2) acid equivalent (a.e.)
  • 1) a.i. calculation
  • - a.i. is always identified on the herbicide
  • - often expressed as either a or in g/L.
  • - calculations based on dry or liquid

  • Several calculations to determine the amount of
    a.i. applied. One of the easiest calculations
  • g a.i. applied per ha
  • kg or L of product applied X g active
  • ha L or kg of product
  • Example calculation of dry formulation
  • - Herbicide Plantgard with 30 2,4-D (note 30
    w/w in trade
  • formulation 30g a.i. in 100g product or 300g
    a.i. in 1kg product)
  • - Spray recommendation 2.5kg product / ha
  • - How much is the 2,4-D in the product when we
  • 2.5kg of Plantgard per ha???

  • g a.i. applied per ha
  • kg or L of product applied X g active
  • ha L or kg of product
  • 2.5kg Plantgard X 300g 2,4-D
  • ha 1kg Plantgard
  • Answer 750g a.i. 2,4-D per ha applied when
    spray at recommended rate of 2.5kg
    Plantgard per ha

  • Example calculation of liquid formulation
  • - Herbicide Gramoxone with 35 paraquat (note
    35 w/v in
  • trade formulation 35g a.i. in 100mL product or
    350g a.i. in 1L product)
  • - Spray recommendation 3kg a.i. paraquat / ha
  • - How much is the Gramoxone required when we
  • 3kg a.i. paraquat per ha???
  • g a.i. applied per ha
  • kg or L of product applied X g active
  • ha L or kg of product
  • 3kg paraquat per ha ?L Gramoxone X 350g

  • ha 1L Gramoxone
  • Answer 8.57L Gramoxone is required for 1ha when
  • with 3kg a.i. paraquat per ha

  • 2) Acid Equivalent (a.e.) calculation
  • Herbicides a.i. usually in parent acid form (its
    herbicidally active form), but many are
    formulated as a derivatives (i.e. esters, salts,
  • Alterations with herbicide molecules that are
    acids (at carboxyl COOH structure).

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  • Why would a herbicide be formulated as a
    derivative (ester, salt, amine, etc.) of the
    parent acid?
  • - Increase the ability of the herbicide
  • to penetrate/absorb through the
  • leaf/root much more effectively.
  • - Increase the water solubility of the
  • herbicide
  • a.e. calculation indicates the amount of an acid
    herbicide in a formulation.
  • Some labels indicate both a.i. and a.e. contained
    in the formulation, while others list only one or
    the other.

  • Sometimes, the numbers in formulation do not
    indicate gram active ingredient per L or kg, but
    rather the acid equivalent per L or kg.
  • If the g a.e. is specified on the product label,
    to determine the g a.e applied per ha is
    substitute g a.e for g a.i. in the equation given
  • If not specified, calculate a.e. first using this
  • acid equivalent () molecular weight of the
    acid 1 X 100
  • molecular weight of the herbicide
  • - molecular weight of the acid has to minus (-)
    1 because one H atom is missing when formed
    derivative (H was replaced by the
    salt/ester/amine i.e. NH4 / Na)

  • Example
  • 2,4-D herbicides can be found in ester or amine
  • 2,4-D dietanolamine salt 326 mw
  • 2,4-D acid (pure form) 221 mw
  • of a.e. 2,4,-D 221-1 X 100 67.5
  • 326
  • If in a 2,4-D formulation contains 700g
    dietanolamine salt per L, the g per L a.e. 2,4-D
    in the formulation is
  • 67.5 (a.e.) X 700g/L (2,4-D salt formulation)
  • 100
  • 472.5g is the actual a.i. 2,4-D (in a.e.) that
    cause phytotoxicity to plants/weeds

  • Now, how much g a.e. 2,4-D per ha is applied if
    the spray dosage recommendation is 5L product per
  • g a.e. applied per ha
  • kg or L of product applied X g acid
  • ha L or kg of
  • g a.i. applied per ha 5L X 472.5g
  • ha L
  • 2362.5g a.e. 2,4-D per ha is applied when
    sprayed at the
  • recommended rate of 5L/ha product

  • A technique to help you calculate how much water
    / chemical mix your sprayer puts out to ensure
    that the correct rate of chemical is applied to
    the target plant.
  • 2 types of sprayer knapsack sprayer and
  • Calibration will be emphasized on knapsack

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Knapsack Sprayer Calibration
  • 1) Measure the spray width of the nozzle(s) on a
    dry surface (in m).
  • 2) Spray a test area at the intended pressure and
    walking pace. Record distance (in m) covered in
    one minute (min).
  • 3) Measure the nozzle output in L over one min in
    a measuring jug (L/min). Repeat all steps at
    least twice.
  • 4) The spray volume can be calculated by the
    following formula
  • Application rate (L/ha) nozzle output
    (L/min) x 10,000 m2
  • spray
    width (m) x walking speed (m/min)

  • For example
  • Average nozzle output in 1 minute 3 L
  • Spray width 1 m
  • Average walking speed 100 m/min
  • Application rate (L/ha) 3 x 10,000
  • 1 x 100
  • 30,000
  • 100
  • 300 L/ha application rate (water)

  • How much to put in a tank???
  • The following formula can be used to determine
    the amount of product needed for each tank
  • Product/tank (L or kg) recommended rate (L/ha
    or kg/ha) x tank size (L)
  • application rate (L/ha)
  • For example
  • Recommended product dosage 5 L/ha
  • Application rate 300 L/ha
  • Spray tank size 20 L
  • Calculation
  • Product/tank (L/ha) 5 x 20
  • 300
  • Answer 0.33 L or 330 ml
  • 330 ml of the product is added to a 20 L knapsack
    sprayer to give the recommended spray rate of 5

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