Spray Equipment and Calibration (continued)

AE-73 (Revised), September 2004

Band Application Calibration

The same calibration methods can be used to calibrate band applicators as were used for broadcast spraying. The only difference is the amount of area being covered. The main idea to keep in mind is what is meant by an acre. Total acres refers to the entire acreage in the field. This would include the sprayed band and the area between the bands. A treated acre refers only to the treated area in the band. The spray that would be discharged on a broadcast rate is concentrated in a narrow band by the ratio of the row spacing divided by the band width (see the following example). In band spraying, the row spacing and the nozzle spacing are the same.

Unless otherwise specified, chemical application rates are given on a broadcast basis. For band applications, the rate per treated area is the same as the broadcast rate, but the total amount of pesticide used on a field is less because only a portion of the field is treated.

Spray discharge charts furnished by manufacturers for band nozzles are usually listed as applying chemical on a broadcast basis. The amount applied will increase when directed into a narrow band.

Band Calibration

1. Determine travel speed in the field you will be spraying. Drive at a uniform speed and measure the time to drive 300 feet.
2. Convert the time to travel speed in MPH from Table 14.
3. Check for nozzle uniformity, and if variation is more than 10 percent from the average, replace the nozzles. Determine the application rate in GPA by using one of the three calibration methods.
4. The answer is the application rate per total acre.
5. 
   

   Rate/total acre (GPA) x row width (in)
   	= Rate per treated acre
   band width (in)

Example: In nozzle manufacturer charts, gallons per acre means volume applied to the area sprayed (treated acre). Depending on row spacing and band width, this area is some fraction of the total field. The following shows the higher volume discharged in a treated acre when the broadcast rate is determined:

5 GPA measured with the broadcast calibration method.
30-inch row spacing
10-inch band width

5 GPA x 30-inch row spacing
	= 15 GPA being applied in the band
10-inch band width

Table 16 can be used to find the concentration effect of directing the spray from the broadcast rate to band application. Multiply the GPA found on the broadcast basis times the factor in Table 16.

Table 16. Conversion factor to convert broadcast rate (rate per total acre) to band rate (rate per treated acre).
Band Width (in.)	Row Spacing (inches)
	20	30	36	40
8	2.5	3.8	4.5	5.0
10	2.0	3.0	3.6	4.0
12	1.6	2.5	3.0	3.3
14	1.4	2.1	2.6	2.9

With 15 GPA being applied in the row (treated acre), MIX THE CHEMICAL IN THE SPRAY TANK BASED ON THIS RATE. Do not mix it on the 5 GPA (total acre) rate or you will be applying chemical in the row at three times the desired rate. If you do not want to apply water in the row at 15 GPA, a smaller nozzle would be needed. Refer to the charts in the nozzle manufacturers catalog.

Hand Sprayer Calibration

Hand sprayers are usually used for applying chemicals to small areas. Hand sprayers may be calibrated as follows: determine the square feet in an area, measure the output of the hand gun for one minute, and calculate how fast the measured area should be covered. Then mix enough chemical to cover the area and apply all the chemical to the area as evenly as possible.

Example: You measure an area 21 feet by 21 feet. This is approximately 1/100 acre. Your handgun puts out ½ gallon in one minute and the chemical should be applied at the rate of 25 gallons per acre. In this case: 1/100 acre = .01 ac.

Gallons = 25 GPA x .01 ac. = .25 gallons

If the area should be covered with one quart of spray and your handgun puts out 1/2 gallon per minute, you should cover the area in:

.25 gal
	= 0.5 minutes or 30 seconds
.5 gal/min

How Much Chemical to Put in the Tank

To determine the amount of pesticide to add to the spray tank, you need to know the recommended rate of pesticide, the capacity of the spray tank, and the calibrated output of the sprayer.

The recommended application rate is usually indicated as pounds per acre for wettable powders and pints, quarts, or gallons per acre for liquids. The recommendation can also be given as pounds of active ingredient (lb. AI) per acre rather than the amount of total product per acre. The active ingredient must be converted to actual product.

Be sure your spray tank has accurate markings on the side so you can determine the amount of spray mix remaining in the tank. This is needed so you don’t add more or less chemical than is needed. Be sure to place your sprayer on level ground so an accurate reading can be made.

Most pesticides are sold as formulations in which the active ingredient (AI) is combined with a carrier of water, oil or an inert material. Once you’ve chosen the chemical and the formulation, you must determine the amount of spray mix needed for the application. This will depend on the tank size, the spray volume per acre, the acres to cover and the required application rate given on the product label.

Example: A liquid recommendation calls for 0.5 pound of active ingredient (AI) per acre. The pesticide contains 4 pounds (AI) per gallon formulation. The sprayer being used has a 500 gallon tank and is calibrated at 8 gallons per acre. How much product should be added to the spray tank?

Step 1. Determine the number of acres that can be sprayed with each tankful.

Tank capacity (gallons per tank)		500
	=		= 62.5 acres per tankful
Spray rate (gallons per acre)		8

Step 2. Determine the amount of product needed per acre by dividing the recommended AI per acre by the concentration of the formulation.

0.5 lb. AI per acre
	= .125 gallon or 1 pint per acre
4 lb. AI per gallon

One pint of product is needed for each “acre’s worth” of water in the tank to apply 0.5 pound of active ingredient (AI) per acre.

Step 3. Determine the amount of pesticide to add to each tankful. Each tankful will cover 62.5 acres (Step 1), and 1 pint of product per acre (Step 2) is needed. Add 62.5 pints (62.5 acres x 1 pint per acre = 62.5 pints) of pesticide to each tankful. This is equal to 7 gallons and 6.5 pints of chemical.

Example: A dry product recommendation calls for 2 pounds of active ingredient (AI) per acre. The product is an 80 percent dry flowable. The sprayer is calibrated for 9 GPA and the tank holds 540 gallons. How much product should be added to the spray tank?

Step 1. Determine the number of acres that can be sprayed with each tankful.

Tank capacity (gallons per tank)		540
	=		= 60 acres per tankful
Spray rate (gallons per acre)		9

Step 2. Determine the pounds of product needed per acre. Because not all of the material in the bag is active ingredient, more than 2 pounds of the product must be added to each “acre’s worth” of water in the tank. How much more? The calculation is: divide the percentage of active ingredient (80) into the total (100) and multiply by the active ingredient needed per acre. This gives the pounds of product to add to the tank for each acre covered.

2 lb. AI per acre x 100
	= 2.5 lb of product per acre
80

Two and one half pounds of product is needed for each “acre’s worth” of water in the tank to apply 2 pounds of active ingredient per acre.

Step 3. Determine the amount of pesticide to add to each tankful. Each tankful will cover 60 acres (Step 1) and 2.5 pounds of product per acre is needed (Step 2). Add 150 pounds (60 acres x 2.5 pounds per acre = 150 pounds) of product to each tankful.

Adjuvants (Spreaders – Sticker, Surfactant, Etc.)

The manufacturer may recommend a small amount of adjuvant be added in addition to the regular chemical. This recommendation is often given as “percent concentration.” If an adjuvant at a 0.25 percent concentration by volume is recommended, how much should be added to a 500-gallon tank?

Solution 1:

1 percent of 100 gallons = 1 gallon
NOTE: 1 percent = 0.01

(100 gal x 0.01 = 1 gal)

0.25 percent = 0.0025

0.0025 of 100 gallons = .25 gallons or 1 quart

You will need 1 quart per 100 gallons, or 5 quarts for 500 gallons (.25 x 5 = 5 qts)

Chemical Mixing and Disposal of Excess Pesticide

All agricultural chemicals should be handled carefully to avoid accidental spills and contamination. Because some minor spillage and runoff of sprayer wash water is almost inevitable when working with pesticides, it is wise to load and clean the sprayer on a mixing-loading pad. The pad will contain spills and rinsate and allow it be to be pumped into a holding tank for later use as makeup spray water or for proper disposal.

The pad can be constructed of sealed concrete or made from appropriate fabric when portability is desired. The handbook “Designing Facilities for Pesticide and Fertilizer Contain-ment,” MWPS-37, from the Midwest Plan Service has many ideas and suggestions for constructing these facilities. This book is available through your local county agent office or from Extension Agricultural Engineering at North Dakota State University.

The best disposition of chemicals is to use them according to label directions. To minimize disposal problems, buy and mix only the quantities of chemicals that you need. When small quantities of pesticide must be disposed of, apply them to the same crop in another location or to another crop and pest for which the pesticide is labeled. Check the label carefully to be certain that the chemical is registered for this alternate application.

Cleaning Equipment

A practice that is gaining acceptance is to carry an auxiliary tank of clean water on the sprayer that can be used to wash down and rinse the sprayer in the field. This leaves the diluted spray material in the field and permits the sprayer to return to the pad “clean,” thus eliminating an accumulation of chemical wash water that would need to be disposed of later. A suggested plumbing arrangement showing water tank and valve locations is shown in Figure 30. The water tank and wash nozzles can be added to most sprayers.

Figure 30. Sprayer field wash system. (20KB b&w illustration)

Triple-rinse the inside of the sprayer using 5 to 10 gallons of clean water for each rinse. Circulate the rinsate through the sprayer and spray it across the field on an approved crop. Repeat the rinse procedure two more times. Also, never drain surplus pesticide or rinsate where it can run off into streams, lakes or other surface water, or where it can contaminate wells and groundwater.

To remove residues of oil-based herbicides, such as esters of 2, 4-D and similar materials, rinse the sprayer with a spray tank cleaner available from most pesticide dealers.

After rinsing the equipment with oil or a water-detergent, fill the tank one-fourth to one-half full with a water-ammonia solution (1 quart of household ammonia to 25 gallons of water) or a water-trisodium phosphate (TSP) solution (1 cup TSP to 25 gallons of water). Circulate the solution through the system for a few minutes and let a small amount go through the nozzles. Allow the remainder of the solution to stand at least six hours, then pump it through the nozzles. Remove the nozzles and strainers and flush the system twice with clean water. Equipment in which wettable powders, amine forms, or water-soluble liquids have been used should be thoroughly rinsed with a water-detergent solution (2 pounds of detergent in 30 to 40 gallons of water). Water-soluble materials should be treated as water-soluble liquids. Allow the water-detergent solution to circulate through the system for several minutes. Remove the nozzles and strainers and flush the system twice with clean water.

When it is time to store your sprayer, add 1 to 5 gallons depending of the size of your tank, of anti-freeze (ethylene glycol) and water or recreational vehicles (RV) anti-freeze before the final flushing. As water is pumped from the sprayer, the anti-freeze will leave a protective coating inside the tank, pump, and plumbing.

Container Disposal

Returnable, reusable containers are recommended if they are available because they eliminate disposal problems. Recycling is a solution to non-returnable containers; approximately 48,000 were recycled in 1995. When this is not an option, proper disposal of empty pesticide containers is very important. Empty containers should not be left around as they pose a hazard to the area, animals and people.

Empty liquid containers must be triple-rinsed or power-rinsed before disposal. After completely draining the contents into your sprayer, rinse it by filling it at least 1/10 full of water, capping it, then shaking until all inside surfaces have been rinsed. Empty the rinse water into the spray tank. Drain the container completely (at least 30 seconds) and repeat the rinse process two more times, adding the rinse water to the spray tank.

Triple-rinsing is slow and tedious. An easier and faster way is to use a power rinse device that attaches to a hose and pierces the bottom or side of the container (Figure 31). The water spray rinses the container as it drains. A 60-second spray rinse is usually better than a triple rinse. Special rotating nozzles are also available to flush out containers and rinse spray tanks. Rinsed containers should be crushed and disposed of in a waste handling system or recycled if they are returnable.

Figure 31. Power rinse device. (8KB b&w illustration)

If burning of packages is allowed by local ordinances, burn no more than one day’s accumulation at a time. The smoke and fumes from pesticides can be toxic. Burn containers in a location where smoke and fumes do not move toward people or an inhabited area. An alternative to burning is to place empty paper and cardboard containers in a plastic trash bag and dispose of them in an approved waste handling facility.

Approved procedures for disposal of excess chemicals and empty containers have changed frequently. Disposal techniques that are legal today may not be acceptable tomorrow. Check with local authorities on proper methods to use.

Chemical Injection

Injection metering of spray chemicals is another approach to solving many of the handling problems and the disposal of surplus spray tank mix and rinsate.

Injection sprayers are designed so that tank mixing is unnecessary. Because the tank contains only clean water, tank washout between sprays and disposal of any unused chemical mixture is eliminated.

In place of tank mixing, chemicals from a concentrate container are metered and injected into the water being pumped through the sprayer, giving the correct proportion of chemical and water for the needed spray. Injection can take place at various points on the sprayer, depending upon the design. When spraying is complete, the containers of concentrate can be removed to storage and with minimum cleanup the sprayer is ready for another use.

Weights and Measures

Weight
16 ounces = 1 pound = 453.6 gms
1 gallon water = 8.34 pounds = 3.78 liters

Liquid measure
1 fluid ounce = 2 tablespoons = 29.57 milliliters
16 fluid ounces = 1 pint = 2 cups
2 pints = 1 quart
8 pints = 4 quarts = 1 gallon
8 ounces = 1 cup

Length
3 feet = 1 yard = 91.44 centimeters
16 ½ feet = 1 rod
5,280 feet = 1 mile
320 rods = 1 mile

Area
9 square feet = 1 square yard
43,560 square feet = 1 acre = 160 square rods
640 acres = 1 square mile

Speed
88 feet per minute = 1 mph

Volume
27 cubic feet = 1 cubic yard
1 cubic foot = 1,728 cubic inches = 7.48 gallons
1 gallon = 231 cubic inches

Common Abbreviations and Terms Used With Pesticide Sprayers
GPM = Gallons Per Minute
GPA = Gallons Per Acre
PSI = Pounds Per Square Inch
MPH = Miles Per Hour
RPM = Revolutions Per Minute
GPH = Gallons Per Hour
FPM = Feet Per Minute

Using Pesticides Safely

In addition to the traditional recommendations of buying only the right amount of the proper chemicals and being sure they do not get stolen, eaten, drunk, spilled, or misused before you are ready to use them, the following suggestions for use of chemicals in the field are worth reviewing:

1. Read and understand all of the pesticide label before use. The label has detailed instructions on how to use the pesticide wisely. Re-read all bold print.

2. Don’t use a tank mixture of two or more chemicals unless the mixture has label clearance.

3. When pouring and mixing chemicals, be sure the breeze blows the chemical away from you. Wear clean clothes, rubber gloves, and chemical goggles when handling chemicals. Wash all clothing, gloves, and caps before wearing them again.

4. Don’t hurry when using chemicals. Hurrying causes most people to be more accident prone. Spilled chemicals, the wrong chemicals in the sprayer, and the wrong rate of application are examples of problems that rushing promotes.

5. Reduce spray drift by applying chemicals on relatively calm days. Operate the sprayer at the lowest recommended pressure to minimize drift.

6. Mix only the amount of pesticide needed for the job. Use your best judgement when disposing of leftover spray or used containers. As you empty a container, rinse it three times and pour the rinsate into the sprayer tank.

7. Thoroughly rinse sprayer tank and hoses before changing pesticides or repairing equipment. Contamination may not be completely eliminated, but it can be minimized so the resulting hazard to crops and humans is small.

8. Be familiar with symptoms of chemical poisoning. Dizziness, headaches, upset stomach, blurred vision, and excessive sweating are symptoms of poisoning from several pesticides. See a doctor any time you do not feel well and have handled a chemical within the past 12 hours. Take the label along. The label will tell the doctor which chemical has caused the poisoning so corrective action can be done.

9. If a pesticide is spilled on the skin, wash the affected area with soap and water. Remove any contaminated clothing and put on clean clothes before continuing.

References

Chemical Applications In Agriculture, NCR 520, Michigan State University, 1994.
Boom Sprayers, NRAES 19, Pennsylvania State University, 1983.
All About Application Accuracy, Dupont, Wilmington, Delaware, 1982.
A Guide to Field Sprayer Operation, Saskatchewan, 1983.
Spraying Systems Catalog, Wheaton, Illinois.
Delavan Spray Catalog, Lexington, Tennessee.

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For more information on this and other topics, see: www.ag.ndsu.edu

AE-73 (Revised), September 2004