Calibration of Sugarcane Sprayers

Curtis Rainbolt, Ron Rice, and Les BaucumUniversity of Florida/IFAS

Calibration• Mathematical determination of the amount of spray

solution (water) applied in gallons per acre (GPA)• Insures that the appropriate amount of herbicide is

applied• The GPA can be changed by adjusting one or more of

the following:– Pressure– Nozzle size– Ground speed– Spacing of nozzles on spray boom

• Pressure has least effect on spray volume but important in maintaining proper spray pattern

• Pressure affects spray droplet size and drift

Why Calibrate?

• Proper calibration of sprayers will eliminate the over or under application of herbicides

• Under application – Poor weed control – Need for reapplication – Yield losses due to competition

• Over application – Increased chance of crop injury (narrow margin for some

herbicides)– Environmental pollution (off label application rates)– Increased cost

Cost estimate for over or under application

Under application resulting in re-spray*$30/acre x 100 acres $3,000

$30/acre x 1000 acres $30,000

*Does not include additional time/labor, fuel, and machinery expense

Over application by 10%($30/acre x 10% ) x 100 acres $300

($30/acre x 10% ) x 1000 acres $3,000

($30/acre x 10% ) x 5000 acres $150,000

Nebraska Calibration Survey

• Two of every three pesticide applicators were making significant application errors

• These mistakes were costing farmers from $2 to $15 per acre in added chemical expense, potential crop damage, and threatened weed competition

• 75% of applicators who calibrated more than once per year were within 5% of target

• How would you compare?

Prior to Calibrating

• Inspect your spray equipment– Check for leaks– Look at nozzle spray patterns– Replace all faulty nozzles– Make sure screens are clean

• Determine if application is banded or broadcast

Calibration Procedure

• Determine calibration distance in feet from the table using band width if banding or nozzle spacing for broadcast applications

• To determine the calibration distance for a nozzle spacing not in the table divide 4080 by the nozzle spacing or band width in inches

Nozzle spacing/ band width

(inches)

Required calibration distance (ft)

12 340

18 227

20 204

24 170

36 113

48 85

Calibration (continued)

• Stake out the designated calibration distance– Do this in a field rather than a hard surface to

account for tire slippage that might occur

• With the sprayer in operation record number of seconds it takes to travel specified distance – repeat for accuracy and record tractor used and gear and throttle setting (RPM)

Calibration Procedure (continued)

• With tractor in neutral and the throttle setting determined earlier, collect water from all nozzles for band application or from 1 nozzle for broadcast applications for the required number of seconds

• The number of ounces collected equals gallons per acre on a broadcast basis.

• Check delivery of all nozzles on spray boom and replace if output is off by more than 10%

• Remember that total ounces may represent delivery from more than one nozzle depending on whether the herbicide is banded or broadcast.

Calibration Procedure (continued)

• Ways to increase GPA– Decrease speed– Increase spray

pressure– And/or use a larger

spray tip

To Calculate Treated Acres when Banding• Divide band width (inches) by row

width (inches) and multiply by total number of acres

• Asulox broadcast rate of 4 qt/A– In a 20 acre field the row width is 60

inches and a 36 inch band will be treated. Using the formula above the number of treated acres is 12

– If Asulox is broadcasted, 4 qt will treat one acre; if banded, 4 qt will treat 1.67 acres

– Remember – whether broadcasted or banded the concentration of the herbicide in the water is the same and rate per treated acre is the same

Banded Calibration Example• Asulox applied at a broadcast rate of 4 qt/A

• You are spraying a 36 inch band (3 nozzles) and the row spacing is 60 inches

• If you collect 20 ounces from 3 nozzles/row for time it took to travel 113 ft (36 inch band = 113 ft), then you are applying 20 gallons per acre in the banded area

• A 200 gallon spray tank will treat 10 acres broadcast or 16.6 acres if the spray solution is banded.

• Asulox should be added at 40 qt (10 gallons) to 190 gallons of water.

• Remember the concentration of the herbicide in the water is the same whether applied on a band or broadcast.

Broadcast Example

• Aatrex is being applied broadcast using a boom that has nozzles spaced 20 inches apart

• In the time it took you to travel 207 ft, you caught 15 ounces of water from a single nozzle. Thus you are applying 15 GPA

• You have a 300 gallon tank, so you can treat 20 acres

• For a rate of 4 qts/acre you should add 80 qts atrazine to 220 gallons of water.