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Handheld wind meters
Ever lick your finger and hold it up in the air to gauge wind direction and speed? Tossing blades of grass works, and so does noticing which direction trees blow.
These no-cost wind-detection methods might work well during golf season, but it's a different story during spraying season. There is a good reason why a herbicide like glyphosate is labeled to apply between 2-mph and 10-mph wind speeds. Wind speeds above 10 mph can key off-target movement. If that herbicide you're applying drifts into a nearby vineyard, you could be liable for damages for $5,000 per acre or more.
Pesticides can also move off target when wind is absent, due to inversion drift. “I'm not discounting the severity of a chemical-drift issue due to excess winds,” says Andrew Thostenson, North Dakota State University pesticide program specialist. “But usually in that case, the wind is creating dispersal and evaporation, and you might take out the edges of a neighbor's field. An inversion drift can take out an entire 160-acre field because of the way it moves in a cloud, and there is no dispersal and no evaporation. That's why it can be much worse.”
Immediacy and accuracy
That's where handheld wind meters come into play. These devices enable pesticide applicators to immediately gauge wind speed, wind direction, and other weather data. This information can be used to decide whether to park the sprayer or to commence spraying.
“I have used these and they work well,” says Scott Bretthauer, University of Illinois Extension specialist, pesticide safety education.
Handheld wind meters feature a range of attributes. Some less-expensive units detect just wind speed and temperature. Other more expensive ones mimic mini weather stations. They measure not only wind data, but also dew point, humidity, and other indicators.
Having more data can help you make better spraying decisions. However, avoid getting bogged down by so much data that you get analysis paralysis.
“If you get something complicated, you won't use it,” reminds John Johnston, division manager of WeatherHawk Division for Campbell Scientific.
Here are five features to consider when shopping for a handheld wind meter.
1. Jackknife design. Like a jackknife, the upper part containing the wind-measuring component swings out as you hold the bottom part.
“The jackknife keeps the unit away from your hand,”says Ed Edelman, owner of ambientweather.com.
That's important, because heat generated by a hand can give erroneous readings. The jackknife design also covers the unit's impeller, which is used in calculating wind speed. This helps prevent damage from hard knocks and dust.
Bretthauer advises that you measure where the spray originates. “You need to measure wind speed at boom height, not at cab height,” he says.
2. Durability. Meters in the field will be exposed to wind, rain, dirt, and the occasional drop onto the ground. It's important to have a unit that stands up to tough conditions.
3. Display. Some of these units have large LCD displays, which are easy to read and enable you to make quick decisions. “Smaller LCD displays can be difficult to see sometimes,” notes Johnston. Some units have backlit displays that work well in situations with reduced lighting, he adds.
4. Replacement parts. These units are pretty sturdy. One part that may wear out after several years is the impeller, which measures wind speed. Some units, including Kestrel and WeatherHawk, have removable and easily replaced impellers. Impeller cost hovers around $20.
5. Delta T calculation. Some meters make a Delta T calculation, which is the spread between dry bulb (current air temperature) and wet bulb temperature. Wet bulb temperature is the temperature that's reached if all water evaporates in a parcel of air. For example, this is the temperature you feel when your skin is wet and exposed to moving air.
The Delta T calculation offers a quick guide to determining acceptable spraying conditions. It nixes excessive evaporation rates during application, ensuring that the chemical you apply stays on weeds and crops.
It is not recommended to apply pesticides when Delta T is above 10. A 2 to 8 range is ideal, says Meg Keating, advertising and PR manager for Nielsen-Kellerman.
Handheld Wind Meters
The jackknife design Ambient Weather WM-4 measures wind speed, wind direction, temperature, relative humidity, and compass direction. It calculates wind gust, dew point, Delta T, wind chill, and comfort index. Features fluxgate compass for digital wind direction measurement. Analyzes crosswind, headwind, and tailwind readings with the built-in wind vane.
La Crosse Technology
The EA-3010 handheld anemometer instantaneously measures maximum and average wind speed, wind chill, and temperature in both Celsius and Fahrenheit scales. Minimum to maximum wind speed measured ranges from .44 to 67 miles per hour. Temperature measuring range is from -21.8°F. to 138.2°F. Features a backlit display and a neck band for easy carrying.
Nielsen-Kellerman Kestrel Weather Meters
The waterproof Kestrel 3500 Delta T measures current, average, and maximum wind speed. Displays current temperature, relative humidity, dew point, barometric pressure, and altitude. Makes a Delta T calculation to determine optimum spraying conditions. Includes real-time clock and a large backlit display. Has a thermally adjusted humidity sensor and a user-replaceable impeller.
The WM-300 WindMate features a jackknife water-resistant design that measures current, maximum, and average wind speed, wind direction, humidity, dew point, wet bulb, Delta T, temperature, and wind chill on a large LCD display screen. Contains a fluxgate compass for precise digital wind direction measurement and easy impeller replacement. Calculates crosswind, headwind, and tailwind readings.