Growsafe Spray Application Techniques — Questions and Answers
Question 1: What is the recommended maximum wind speed for ground-based agrichemical spraying in New Zealand?
- Up to 15 km/h, depending on the product and application method (Correct answer)
- No limit if using low-drift nozzles
- Up to 30 km/h with proper equipment
- Spraying is only restricted in completely calm conditions
Correct answer: Up to 15 km/h, depending on the product and application method
In NZ, the general guideline for ground-based spraying is that wind speeds should not exceed approximately 15 km/h, though specific products and regional rules may require lower thresholds to minimise drift.
Question 2: What is calibration of spray equipment designed to ensure?
- The correct volume of spray mixture is applied per hectare (Correct answer)
- The spray pump pressure is at maximum output
- The tractor travels at the fastest possible speed
- The chemical concentrate is used at full strength
Correct answer: The correct volume of spray mixture is applied per hectare
Calibration ensures that the spray equipment applies the correct volume of spray mixture per hectare, which is essential for effective pest control and compliance with label rates.
Question 3: In NZ, what is an inversion layer and why is it dangerous for agrichemical spraying?
- A weather condition where cool air is trapped under warm air, causing spray to hang and drift unpredictably (Correct answer)
- A soil layer that prevents chemical from reaching plant roots
- A type of spray nozzle pattern that inverts the spray cone
- A chemical reaction that inverts the pH of the spray solution
Correct answer: A weather condition where cool air is trapped under warm air, causing spray to hang and drift unpredictably
A temperature inversion occurs when cool air is trapped under a layer of warm air, preventing normal air mixing. Spray droplets can remain suspended in the still, cool air and drift long distances unpredictably, making it dangerous to spray.
Question 4: What nozzle type produces the coarsest droplets to reduce spray drift in NZ conditions?
- Air induction (AI) or low-drift nozzles (Correct answer)
- Hollow cone nozzles
- Fine mist nozzles
- Fan jet nozzles at high pressure
Correct answer: Air induction (AI) or low-drift nozzles
Air induction (AI) or low-drift nozzles produce coarser droplets by mixing air into the spray, which significantly reduces the proportion of fine, drift-prone droplets. They are widely recommended in NZ.
Question 5: What is the purpose of adding a surfactant or wetting agent to an agrichemical spray mix?
- To improve spray coverage and adhesion on plant surfaces (Correct answer)
- To make the chemical less toxic to the operator
- To increase the rate of chemical breakdown in sunlight
- To change the colour of the spray for visibility
Correct answer: To improve spray coverage and adhesion on plant surfaces
Surfactants reduce the surface tension of spray droplets, improving their spread and adhesion on plant surfaces. This is particularly important on waxy or hairy leaves where droplets might otherwise bead up and roll off.
Question 6: Under NZ regulations, what records must be kept when applying agrichemicals commercially?
- Product name, rate, area treated, date, time, weather conditions, and operator details (Correct answer)
- Only the product name and date of application
- Records are only required for aerial application
- No records are legally required for ground spraying
Correct answer: Product name, rate, area treated, date, time, weather conditions, and operator details
NZ regulations and NZS 8409 require comprehensive spray records including product name, application rate, area treated, date and time, weather conditions, operator name, and Growsafe certificate details for commercial applications.
Growsafe Spray Application Techniques
What is the recommended maximum wind speed for ground-based agrichemical spraying in New Zealand?