Explanation:
This method uses a linear calibration course equal to 1/128th of an acre. The output from the sprayer is collected for the time required to travel 1/128th of an acre. Because a gallon is 128 ounces and the course is 1/128th of an acre, the output collected in ounces is equal to the gallons applied per acre. The Travel Distance Table shows how many linear feet the sprayer must travel to give the equivalent of 1/128th of an acre at various nozzle spacings and band or row widths. When the sprayer travels this distance, each nozzle will have sprayed 1/128th of an acre.
Step 1: Distance
Using the Travel Distance Table, find the distance (in feet) you need to travel for your nozzle spacings, band or row widths (in inches). Use nozzle spacing (distance between nozzles on boom) to determine driving distance for broadcast sprays. Use band width (width of the wetted band beneath the nozzle) to determine travel distance for banded sprays (including post-directed herbicide sprays). Use row width for foliar sprays directed to the crop. Mark off this distance in a field, allowing space for the sprayer to reach full operating speed before reaching the first marker of the test course.
ch5-34_table1
To calculate travel distance for spacings or widths not listed, use the following formula:
ch5-34_1
Step 2: Time
Fill the tank half full with water (no pesticide). Make at least two runs over the marked distance with all the equipment (cultivator, disk, planter, etc.) that will be used during the application engaged. Select RPM and gear settings, and record the average time in seconds that the sprayer takes to travel the marked distance without spraying.
Step 3: Output Collection/GPA
Park the tractor and adjust sprayer pressure to the level that will be used for application. Using a container marked in ounces, catch the output from a single nozzle for the length of the average travel time (from Step 2). The number of ounces collected from one nozzle is equal to the output of the entire sprayer in gallons per acre (GPA). (Because you have already determined that output from each nozzle is within 10 percent of the average output as described in the Pre-calibration Checkup section, it is not necessary to collect output from every nozzle during this step).
Note: When more than one nozzle is used per row or band, the spray collected from one nozzle should be multiplied by the number of nozzles directed at the row or band. All nozzles in this group must be the same size and have uniform output. This combined output, in ounces, from all nozzles directed at the row or band is equal to the gallons per acre being applied to that row.
If necessary, make adjustments to obtain desired output. Change pressure for small adjustments. Change speed (and re-calibrate) or nozzle tips for large adjustments.
