Spray application manual
31 January 2025
Module 10: Weather monitoring for spraying operations
10.6 Weather-monitoring equipment
Published 24 January 2025 | Last updated 20 January 2025
Visual clues for assessing wind speed and direction are important for monitoring weather conditions but they are not a substitute for physically measuring wind speed, wind direction, temperature and humidity at the application site.
Measurements of weather parameters should always be taken using an appropriate instrument, such as a weather meter.
Weather monitoring using a hand held meter
24 January 2025Weather monitoring using a hand held meter. Another video from GRDC's Spray Application GROWNOTES™ series.
This video appears in modules 2 and 10.
Bill Gordon: We're looking at weather monitoring in the field for when we're spraying, so I've got a handheld weather meter here. This will tell me things like temperature, humidity, wind speed, and when we're recording these things in the paddock, it's a legal requirement to measure those at the site of application, so a portable meter like this is really handy.
When measuring wind speed, that should be done at about 2 metres in the air. That's the height at which they measure wind speed to judge or calculate the no spray zones or downwind buffers on the label. The other things I need to measure are temperature and relative humidity. That should be done at 1.25 metres and ideally, these little sensors would be shaded, so we don't want to get direct radiation on them. I'd probably turn that away from the sun while I'm doing temperature and humidity, and I need to record those measurements—wind speed, wind direction, temperature, humidity—and generally every load, so with the start of the day, each load and at the end, and I need to make a record of them.
If I'm going to make a decision about whether I keep spraying or not, particularly based on temperature and humidity or delta T. I also want to take a measurement at the target, so I'll take my handheld weather metre and I'll place it down in amongst the weeds or the crop canopy. Because I've got soil moisture or the plants aren't stressed, quite often the humidity will be lower down there, or the droplet survival will be better.
So handheld weather metres are a really useful tool for recording those things out in the paddock, but if I'm going to make a decision about whether I keep spraying as it gets to higher temperatures, I'll measure it down at the target.
Hand-held weather meters
Visual clues for assessing wind speed and direction are important for monitoring weather conditions but they are not a substitute for physically measuring wind speed, wind direction, temperature and humidity at the application site.
Measurements of weather parameters should always be taken using an appropriate instrument, such as a weather meter.
Agricultural compare chart
Permanent weather stations on-farm
Permanent weather stations are particularly useful for capturing and recording long- term weather and climate data, which can be used to analyse on-farm trends.
Permanent weather stations at the farm or enterprise are also useful for comparing measurements with forecast data and historical records to evaluate their accuracy and relevance for your site.
Permanent weather stations are particularly useful for capturing and recording long- term weather and climate data, which can be used to analyse on-farm trends.
Permanent weather stations at the farm or enterprise are also useful for comparing measurements with forecast data and historical records to evaluate their accuracy and relevance for your site.
A well set-up and located permanent weather station on-farm
Locating a permanent weather station
Several factors should be considered when installing a weather station on-farm. Make sure that:
the site is representative of the area that you would be using the weather data for (consider factors such as the elevation compared to the rest of your property);
the vegetation around the site is consistent with the wider monitoring area;
the site is not vulnerable to flooding, fires or lightning strikes;
the site is protected from livestock and vermin;
the site is in an area of reliable communication (e.g. Ultra high frequency or mobile phone);
the site is a suitable distance from structures or obstructions – as a general rule the station should be located a distance at least 10 times the height of the obstruction away from the obstruction (preferably more);
the site is level; and
the orientation of the station is noted, e.g. aligned with grid north or true north.
Drift Reduction Technology an Introduction
2 March 2017An introduction to Drift Reduction Technology. Another video from GRDC's Spray Application GROWNOTES™ series.
Bill Gordon: Many people would have heard of the term DRT or drift reduction technology. From a grower's point of view these are the things that allow us to minimize the amount of product or droplets of that might get into the air while we're spraying. The things that can help reduce drift are things like boom heights, so lowering the boom height as low as practical when you're operating, but still maintaining double overlap
that's one way of cutting down how much product could get in the air.
Another thing that you could do is with your nozzle selection, so choosing nozzles with larger droplets or coarser spray qualities also reduces drift potential. There's other things as an operator you may be able to do for instance your formulation choice or the addition of adjuvants to the tank may also affect droplet size which could cut down drift and all these things when reduced drift reduce the amount of product that can move down wind or away from this sprayer.
When it comes to the APVMA - the guys that aprove products for sale and determine what goes on the label, DRT or drift reduction technologies have a very specific meaning, so on the label there will be approved DRTs which will allow growers to potentially reduce their no spray zone or that downwind buffer distance that's required for some products. The things that may be acceptable on the label in reducing a buffer may be operating at reduced wind speeds, again lower boom heights or changing droplet size. They will also recognize certain formulations as reducing drift.
So from a growers point of view it's always important to check the label and see what technologies or drift reduction technologies will be acceptable if you're looking at reducing a no spray zone.
Portable weather stations
A portable weather station is usually very similar to a permanent station, but instead are usually mounted on a tripod. This means they can be relocated from one paddock to another.
A portable weather station
Local weather station networks
Several growing areas throughout Australia have set up local networks of permanent weather stations that provide remote access for growers and subscribers via UHF radio, mobile phone or the internet.
The benefit of having access to a local network is the ability to compare wind speed and direction at various sites, which can give an indication of when a change is coming through an area. Networked stations are also useful for comparing historical data for an area with official BoM data to identify possible variations.
Users of weather data obtained from this type of network need to be aware that, depending on where they are located, they may not be regarded as being at the site of application. Hence, the spray operator still needs to measure and record conditions at the application site.
The WAND network (Qld and NSW) https://www.goannaag.com.au/wand-app and the COtL network (SA) https://cotl.com.au/ are currently the most geographically extensive networks operating across agricultural production areas of Australia.
These networks provide specific and detailed information on hazardous inversion conditions at the site.
Onboard weather stations
The most useful weather monitoring instrument for spray applicators is one that allows you to measure the weather parameters in real time at the site of application – while you are driving. Weather stations are available that can be mounted on the sprayer that provide live weather data while you are driving the sprayer.
The Airmar onboard weather station
Airmar Sprayer
Some sprayer manufacturers, such as John Deere, are starting to offer these onboard weather stations as options when you order the sprayer, others can be purchased as standalone, portable units that will work on any vehicle.
These systems use an in-built GPS system to determine the sprayer’s position, heading and speed, and ultrasonic sensors to gather the weather data. Using this information, the onboard stations can accurately determine the wind speed and direction, as well as other weather parameters, such as temperature, humidity and DeltaT, while the sprayer is moving. However, without the ability to measure temperature and wind at 10m these systems cannot accurately predict hazardous inversion conditions.
Find out more
For more information about onboard weather stations go to https://www. airmar.com/ Catalog/ WeatherStation-Instruments and www.specmeters. com/weather- monitoring/ weather-stations/ sprayer-station/
Tip
When mounting an onboard weather station, make sure it is placed in a location where it can get clear airflow, and will not be impacted by obstructions or machinery exhaust emissions.