Spraying pastures this summer? Then take the time to calibrate your sprayer for maximum effectiveness. Larry Redmon, extension forage specialist with the Texas Cooperative Extension in Overton, Texas, offers these steps for boom and boomless sprayer application.

Boom
1. Determine nozzle spacing.
2. Refer to the following chart to determine calibration course:
3. Measure and stake off the appropriate calibration course based on nozzle spacing. The course should be on the same type of ground that will be sprayed. (Speeds may be faster on roads than on sod, changing the application rate.)
4. Drive the course in the gear and rpm you will use when actually spraying. Record the time in seconds. Do this twice and average the time.
5. Park the tractor and maintain the same rpm.
6. Turn on the sprayer and catch the water from one nozzle for exactly the same number of seconds that it took to drive the calibration course.
7. Ounces caught = gallons per acre.
8. Check all nozzles. Flow rate should not vary more than 10 percent among all nozzles. Replace any nozzles that do not fall into this range.

Boomless
1. Measure effective swath width.
2. Refer to the following chart to determine calibration course:
3. Measure and stake off the appropriate calibration course based on nozzle spacing. The course should be on the same type of ground that will be sprayed. (Speeds may be faster on roads than on sod, changing the application rate.)
4. Drive the course in the gear and rpm you will use when actually spraying. Record the time in seconds. Do this twice and average the time.

5. Park the tractor and maintain the same rpm.

6. Turn on the sprayer and use a trash bag and bucket to catch the water for exactly the same number of seconds that it took to drive the calibration course. (Note: You can also use a 2-liter soda bottle  —  cut a hole big enough to fit over the cluster nozzle in the side of the bottle in place of a trash bag.)

7. Pints caught = gallons per acre.

8. Check all nozzles. Flow rate should not vary more than 10 percent among all nozzles. Replace any nozzles that do not fall into this range.

To find out more, visit the Texas A&M University Forage Web site at http://forages.tamu.edu