Growsafe Spray Equipment Calibration 1 — Questions and Answers
Question 1: What is the purpose of calibrating a boom sprayer?
- To verify that the sprayer delivers the correct volume of product per hectare as specified on the product label (Correct answer)
- To check that the boom is horizontally level
- To confirm that all nozzles produce the same droplet size
- To determine the correct mixing ratio before filling the tank
Correct answer: To verify that the sprayer delivers the correct volume of product per hectare as specified on the product label
Calibration ensures the sprayer applies product at the correct rate. Incorrect application can lead to crop damage, pest control failure, excessive residues, or waste of expensive product.
Question 2: What variables must be known to calculate the application rate (L/ha) of a boom sprayer?
- Nozzle flow rate, travel speed, and boom nozzle spacing (Correct answer)
- Tank capacity and mixing ratio only
- Boom height and weather conditions only
- Nozzle age and last maintenance date only
Correct answer: Nozzle flow rate, travel speed, and boom nozzle spacing
Application rate (L/ha) is calculated from nozzle flow rate, travel speed, and nozzle spacing. Changing any one of these variables changes the application rate.
Question 3: How is nozzle output typically measured during calibration?
- By collecting the output of individual nozzles for a set time and measuring the volume collected (Correct answer)
- By counting the number of droplets per square centimetre on water-sensitive paper
- By weighing the spray tank before and after a calibration run
- By measuring the pressure at the boom inlet gauge only
Correct answer: By collecting the output of individual nozzles for a set time and measuring the volume collected
Collecting nozzle output for a timed period (e.g., 1 minute) and measuring the volume in a graduated cylinder is the standard practical method for checking individual nozzle flow rates.
Question 4: What is the maximum allowable variation in output between nozzles on the same boom?
- Typically no more than 5-10% variation between nozzles — nozzles outside this range should be replaced (Correct answer)
- Up to 50% variation is acceptable if the average rate is correct
- No variation is ever acceptable — all nozzles must deliver identical output
- Up to 25% variation is acceptable if the boom is wider than 12 metres
Correct answer: Typically no more than 5-10% variation between nozzles — nozzles outside this range should be replaced
A maximum 5-10% variation between nozzles is the standard acceptable tolerance. Greater variation leads to uneven application, with some areas under- or over-treated.
Question 5: What does 'travel speed calibration' involve?
- Measuring the time taken to travel a known distance to confirm actual ground speed matches the assumed speed (Correct answer)
- Checking that the tractor can travel in a straight line
- Confirming the GPS display is accurate to within 1 km/h
- Measuring the total distance covered in one tank-load
Correct answer: Measuring the time taken to travel a known distance to confirm actual ground speed matches the assumed speed
Travel speed is measured by timing travel over a known distance. Any variation from assumed speed changes the effective application rate, so actual speed must be confirmed.
Question 6: What effect does worn nozzle tip have on application rate?
- Worn nozzles deliver a higher flow rate than rated, causing over-application (Correct answer)
- Worn nozzles always block and reduce flow, causing under-application
- Wear has no significant effect on nozzle output until the nozzle fails completely
- Worn nozzles change the spray angle but not the flow rate
Correct answer: Worn nozzles deliver a higher flow rate than rated, causing over-application
Nozzle tips wear with use, enlarging the orifice and increasing flow rate beyond the rated output. This causes over-application of product, leading to potential residue and phytotoxicity problems.
Growsafe Spray Equipment Calibration 1
What is the purpose of calibrating a boom sprayer?