This document discusses calibrating a knapsack sprayer for effective and safe herbicide use. Calibration ensures the correct herbicide rate is applied to avoid crop damage, pollution, and waste. It should be done when starting with a new sprayer, at the start of each season, after nozzle or pressure changes, or after 100 hectares of spraying. Key factors that affect calibration include canopy density, nozzle type and pressure, and ground conditions. The calibration process involves measuring the operator's walking speed, sprayer output, and swath width to determine the spray volume applied per hectare.

1. WORKSHOP ON EFFECTIVE
AND SAFE USE OF
HERBICIDES
Udensi U. E.

2. EQUIPMENT CALIBRATION
(KNAPSACK)

3. • WHAT DOES CALIBRATION
DO?
Sprayer calibration:
(1) readies your sprayer for
operation and
(2) diagnoses nozzle tip
wear and this will give you
optimum performance of
your tips and equipment

4. EQUIPMENT CALIBRATION- KNAPSACK
 Calibration of sprayers is an important
activity in any weed control or spraying
program. It ensures that herbicide active
ingredient is applied correctly at the
product labelled rate. Application in
excess of the recommended rate can lead
to the following:
• Crop damage
• Environmental pollution and
• Use becomes uneconomical.

5. WHEN DO WE NEED TO CALIBRATE A SPRAYER ?
 Calibration can take place as follows:
• When spraying for the first time with a new sprayer
• At the beginning of each season
• After changes of nozzle tips, spraying pressure or
speed
• When the sprayer has done close to 100 ha of
spraying

6. Factors that may affect calibration
 Canopy height/density of target species
Canopy density and height of vegetation may affect calibration. Low
vegetation and/or scattered clumps will require less solution per
hectare than taller and dense vegetation with greater leaf surface.
 Nozzle and pressure
The first step in sprayer calibration is to determine the correct nozzle type
and size (flow rate) . Therefore it is important to select the correct nozzle
material. Nozzle size depends on the desired application rate, ground
speed and nozzle spacing. For most herbicide application using knapsack
sprayers the suggested pressure ranges from 100 to 200 kPa (15 - 30
psi)
 Ground conditions of area
For knapsack sprayers the ground conditions (slash, slope, undulating, etc.)
will affect the workers walking speed, which directly affects the delivery
rate per hectare. If conditions vary substantially within the site or
from site to site, the equipment should be recalibrated.

7. Calibrating a knapsack
sprayer Three measurements are important when
calibrating a new and old knapsack -
1. The walking speed of the operator
expressed in meter per second or kilometres
per hour (Km/h)
2. The output per minute of the sprayer
expressed in Litres
3. The width of each pass of the sprayer,
commonly known as the Swath Width
expressed in metres.

8. Sprayer Calibration
• Importance
• Procedure
• Area volume method
• Time-volume method

9. Steps in Knapsack Sprayer Calibration
 Carry out a pre-operation service and prepare the
sprayer for the job.
• Install the appropriate spray tip (nozzle)
• Partially fill the sprayer with clean water and dye.
• Pump up the spray unit to a selected pressure
• Ensure there is no leakage from equipment.
• Test spray sample cards to check spray droplet
pattern. If necessary adjust or change nozzles and
pressure to achieve desired spray droplet pattern.
 Measure the effective swath width of the nozzle

10. Steps in Knapsack Sprayer Calibration-Contd.
 Mark out a 50m2
calibration plot in the area to be
sprayed with a peg in each corner.
 Fill the sprayer to a known level or mark.
 Spray the calibration plot at the pressure and speed
you will use when you do the job.
 When you have finished spraying the calibration
plot, Note the amount of water taken to refill the
tank to the original level or mark.
 Calculate the litres used and determine spray
output in litres per hectare

11. Thank you