Reducing your chances for spray drift
Tips to limit spray drift and avoid drift complaints
Today more than ever, it’s critical to avoid spray drift on your farm. Here is a list of important steps to help you reduce the chances of drift, which could result in any number of complaints or issues for your operation.
Monitoring and recording field conditions
You can do everything correctly with your equipment and application prep, and still experience drift or even get drift complaints. That is why monitoring and recording all of your activities is a crucial step before you spray.
How to measure and accurately record environmental conditions at the field location¹:
- Document any instrument you’re planning to use by recording the manufacturer and model number. Buy one of many types of accurate portable weather instruments that log and store data, and aid in auditing and record-keeping. Some devices even have Bluetooth/wireless capabilities.
- Environmental measurements to take:
- wind speed and direction
- temperature (6 tips for spraying in warm weather)
- relative humidity
- At a minimum, record data at the start and finish of the job. Consider recording more frequently as conditions change or for a lengthier spray job. For example, record observations when tank refilling for larger fields. Timestamp all observations with a.m., p.m., or military time, consistently.
- Take meteorological readings as close to the application site as possible. Be aware that the weather data received via a smartphone or local weather station may not be precise for the location being sprayed.
- Note the specific location where the measurement was made: GPS coordinates, field entry point, field location, etc. Check the product label to see if it requires a specific observation location or distance in relation to the treatment area.
- Make all measurements as close to the nozzle release height (boom height) as possible and in an area not protected from the wind by the spray machine or your body. For aerial applications, 6 feet is suggested when using a hand held instrument.
- Record wind speed for 1 to 2 minutes and take an average. Also, note the time the observation was recorded. Most instruments give an average over a period of time. Make sure the instrument’s anemometer is facing directly into the wind.
- Do not record winds as variable or with a range (i.e. 4 to 8 mph). An average gives a better indication of true wind speed. Light and variable winds, where directions may change several times over a short period, can be more problematic than higher speed winds in a sustained direction. Double check any label restrictions on wind speed.
- Wind direction requires a similar averaged measurement. Many pro and custom applicators record direction in degrees magnetic from a compass (0-360°) instead of alphabetic characters — such as N, S or NW, for example — to indicate wind direction. The key for determining wind direction is to have an accurate assessment method that you use consistently, such as watching trees limbs dust movement, or, even better, set a ribbon on a short stake. Face directly into the wind and record the direction the wind is coming.
- Record temperature and humidity. They can be helpful in determining conditions when spray drift is more likely. Record both temperature and humidity well before and after the application. Take temperature measurements with the instrument out of direct sunlight.
PRO TIPSpray drift from temperature inversions is a big problem. What seems like the best weather for an application, may actually be the worst because of surface or field level temperatures versus those at 10-20 feet higher — they impact how quickly air is traveling up from the ground.
Measuring air temperature differentials (the differences between highs and lows) is a good metric for determining if the field has temperature inversion potential. During an inversion, air closer to the ground is cooler, denser and heavier than the air higher up, which impacts conditions for how spray droplets may drift.
- Be alert to field level temperature inversion conditions, which typically occur from late afternoon, and can be sustained through the night, and into the next morning. Inversions can also start mid-afternoon. Look for the presence of ground fog, smoke layers hanging parallel to the ground, dust hanging over the field/gravel road, heavy dew, frost, or intense odors (for example, smells from nearby manure or stagnant water from ponds are often held close to the ground surface when inversion conditions exist). Believe it or not, inversions often occur in calm air, with low (less than 3 mph) to no wind speeds.
- Make a note of in-field and edge-of-field terrain, including vegetation differences, tree lines, buildings, etc.
- Initial or sign all records, measurements and notes to indicate who made the observation(s) and so you can easily refer to them over time, if needed.
- Speak with your neighbors to find out what is planted across the road or in their fields. Open communication with your neighbors is a valuable step in preventing drift issues.
Remember, avoiding spray drift is the responsibility of the applicator.
That means you, the do-it-yourself (DIY) farmer, must think through the same field conditions as a custom applicator would: how best to spray the field, what products and tank mixes to consider for an application, or even determine if it would be best not to spray the field at that particular time. With proper planning, record keeping and organization, you can make good decisions about spray timing and limit concerns about spray drift.
Wolf, B. (July, 2017). Application Recordkeeping: Focus on Environmental Conditions. Retrieved from: http://sprayers101.com/application-recordkeeping-focus-on-environmental-conditions/
Enz, J., Hofman, V., & Thostenson, A. (2017, November). Air Temperature Inversions. Retrieved from https://www.ag.ndsu.edu/publications/crops/air-temperature-inversions-causes-characteristics-and-potential-effects-on-pesticide-spray-drift