Need for speed

 

In part one of this series, we looked at the first step to optimizing your sprayer efficiency and effectiveness: figuring out what kind of coverage you want, and how much liquid you need to apply to an area to achieve the kind of coverage you want.

 

In part two, we will discuss an important step in sprayer calibration: travel speed.

 

“People buy a sprayer and they just load it up and go thinking the company that built it understands their needs,” said Randy Zondag, Commercial Horticulture/Natural Resource Educator and Director, Lake County Extension. “They don’t.”

 

That’s why it’s so important to calibrate your sprayer to ensure it is providing the disease control you need. There are three things growers can measure to determine sprayer output: travel speed, nozzle size, and pressure in the sprayer itself.

 

Many growers have sprayers mounted to older tractors that lack a speedometer. This can be a problem, because consistent speed is necessary to maintain a consistent spray.

 

“Travel speed is important to calibration, because you have to know how fast you are traveling to know how much area you’re covering,” Zondag said. “That determines your flow rate. Flow rate per time is what we’re looking at, and travel is part of time.”

 

So how do you determine that you are traveling at a consistent speed? Zondag said most nurseries in Lake County use steel poles and paint them white. Other colors may blend in with the plants and get trampled by tractors.

 

“We paint them white so people don’t hit them,” he said. “It’s easy to see.”

 

Then, the poles are spaced 88 feet apart. Why exactly 88 feet apart? That number is an important part of the equation for travel speed, because 88 feet per minute is equal to 1 mph. In the equation, velocity (V) is equal to 60 divided by the time in seconds it takes to travel that 88 foot distance. Once you solve for V, you know how fast that unit is traveling.

 

“If it takes me 20 seconds to travel 88 feet, 20 into 60 is three, so I am traveling 3 mph,” Zondag said. “If I travel 30 seconds in 88 feet I’m traveling 2 mph.”

 

It’s important to measure the speed, because traveling too fast or too slow becomes a problem. If you go too fast, you won’t cover all the plants you need to cover. If you go too slow, you will oversaturate and lose sprayer efficiency. For optimal coverage with an air-assisted sprayer, aim for your tractor traveling between 2.5 mph and 4 mph.

 

If you have one, a radar gun works too. Zondag suggests running the trial even if your tractor has a speedometer, because tractor speedometers are usually not accurate. Also, tractors change speeds as they drive up and down hills in a nursery. To account for that, always run the trial three or four times to get an average. Use the average, because that velocity figure rarely stays in the same place.

 

The most important thing about calibration, Zondag said, is actually doing it.

 

“If you want to calibrate sprayers and don’t know how to do it, find somebody who can walk you through the process,” he said. “This is not rocket science, but it does take time. If you do it right the first time and you train people to do it, you can not only get better at it but you can save money.”

 

·         Setup an 88 ft long distance in a flat field

·         Measure the time that the sprayer travels the 88 ft. distance

·         Use the following equation to calculate the speed

·         V=60/T

·         V is the travel speed in mph

·         T is the time in seconds for the sprayer traveling the 88 ft distance

·         Repeat two or three times and take an average