Q: I’m thinking of trying variable rate fungicide applications this season.
How do I know if my sprayer is capable of varying rates?
A:The first call I would make would be to the GPS specialist from the dealership you bought your sprayer. Have ready the year and model number and GPS equipment it is geared up with. Almost all new models of sprayers come with the proper plumbing to do variable-rate (VR) applications.
If your sprayer has the ability to shut off sections of the boom to eliminate overlap, it’s likely capable of VR fungicide applications. You may have to then investigate if your field computer is capable of reading VR prescriptions. Many field computers are sold with the ability to vary the rate of a single-source product — in this case, water.
You’ll need to work with an agrologist to decide on your label rates and speed and vary the water volume across the zones. When you hit a very poor or washed-out area requiring no application, a zero rate is assigned to shut off either a section or the entire boom depending on the size of the washout (see image). Some sprayer units are capable of applying zero rates on small areas the size of truck, other sprayers will only shut off the booms in larger areas. Consult with your local sprayer specialist; they will be able to tell you exactly how small of an area you would be able to apply a zero rate.
In our experience John Deere GS2/GS3 monitors effectively apply a zero (off) rate at each section individually from reading the zone prescription without any modifications. Raven Viper Pro monitors will require extra prescription setup that labels the zero (off) rate zones as “no-spray zones” to effectively work with sectional control.
Once you hear back from your GPS specialist and they assure you your sprayer unit will work for VR you can then contact an imagery provider. They can share their experience with you and provide a test prescription. This test prescription can easily be made of your local home quarter and uploaded into your field computer to test with water. If everything works fine with the test prescription, the next step would be to acquire some aerial imagery, come up with a plan, ground truth, make a prescription and load the prescription into the sprayer.
JustinCleaverisageo-coachwithAgri-Trend GeoSolutions,Inc.andworksforSureGrowth TechnologiesnearLangenburg,Sask.