aAll nozzle numbers are Teejet brand. Other manufacturers will have comparable nozzles.

To obtain maximum insect and disease control, growers should mount their spray nozzles at an angle to the sprayed surface. Although fungicides and insecticides can be applied with hollow cone and solid cone nozzles mounted perpendicular to the sprayed surface or crop, angling the nozzles about 15 degrees in the direction of the forward travel of the sprayer will help stir plant leaves and foliage to give more thorough coverage, especially on the underside of the leaves. The Spraying action is more vigorous when mounted in this position. This mounting methods works well for both horizontally and vertically mounted nozzles.

Most sprayers are constructed with the nozzle bodies mounted perpendicular to the surface to be sprayed. This does not appreciably affect application efficiency when mounted perpendicular to the soil or plant surface. flood and rain-drop type nozzles must be oriented at an angle to obtain uniform application rates.

Flood nozzles used for application of herbicides give best application uniformity when mounted at 45 degrees to the perpendicular. Rain drop and swirl chamber nozzles, which produce large droplet sizes, should be mounted 15-3- degrees from a straight-down position. Nozzle spacing and boom height are critical to proper overlap and uniform coverage with flood and rain-drop type nozzles. A boom height of 14 inches and a nozzle spacing of 40 inches is ideal for there nozzles.

Having a sprayer system that can be used for a wide variety of needs is essential for most producers. Such a system can save time, storage space and money. Many producers will need more than one application system when spraying crops. A producer growing strawberries, tomatoes and blackberries cannot use the same boom design for all three crops. Even the pump needs may change when spraying more than one crop. This problem can be easily solved by having more than one boom and more than one pump for a spraying system. Booms can be designed to be easily removed and replaced with other boom shapes. The connections to the pump can be reconnected with quick-change connectors which simply plug into each other. This eliminates the need to loosen hose clamps and connections every time a change is needed. Pumps can be exchanged on a sprayer using the same type of quick-change connectors. This type of flexibility can make one sprayer very versatile with respect to several spraying needs.

Crop protection chemicals are most effective when applied at proper rates. Recommended rates are usually found on the chemical label, or they may be recommended by an extension service agent or other technical representatives dealing with application of agricultural chemicals. Applying too much chemical can injure a crop and greatly increase the cost per acre for application. Applying too little pesticide can result in inadequate and undependable control. A second application may be required to achieve adequate pest control. Time, labor and expense of a second application increases the total cost for treatment of a given acreage. Proper calibration assures safe, economical and effective pest control.

Sprayer calibration is the process of adjusting the sprayer to apply a desired rate of chemical in gallons per acre. Broadcast type sprayers are usually the easiest to calibrate due to the simple design and spacing of nozzles. To calibrate a broadcast sprayer, measure the distance between the nozzles on the boom in inches and convert to feet by dividing the distance in inches by 12. For example, a 20 inch nozzle spacing is very common on broadcast sprayers. Dividing 20 /12 gives 1.666 feet. Next, divide 340 by the nozzle spacing in feet. In this example we would divide 340 by 1.666 to get 204. 204 is the distance in feet to lay out a calibration course. Drive the sprayer the length of the calibration course at least twice to get an average time. Make sure you operate the sprayer at the desired ground speed you want to use when spraying your crop. Note the engine speed in RPM's and the gear selection you have chosen for spraying. Always use this engine speed and gear selection when you wish to apply the same rate of material with the same nozzles and pressure.

Now, park the sprayer and with the engine running at the same RPM's you have chosen, set the spraying pressure at the desired rate and catch output from each nozzle for the same length of time it took you to drive the length of the calibration course. Catch the output from each nozzle individually in a container graduated in fluid ounces. Each ounce of spray you catch from each nozzle is the application rate in gallons per acre. For example, if you catch 22 ounces from a nozzle, the application rate of that nozzle is 22 gallons per acre.

All nozzles should be applying approximately the same amount of spray material. Variation among nozzles should be no more than 10 percent and, preferably, no more than 5 percent. If any nozzle is not within 10 percent or less of the average of all nozzles, replace that nozzle with a nozzle that fits the average of the other nozzles.

If you need to reduce the amount the sprayer is applying, you can make minor adjustments by reducing the spraying pressure or increasing the forward ground speed. To make an adjustment more than 25 percent of the current application rate of the sprayer, change the size of the nozzle tips. If you need to increase the application rate, increase the spraying pressure or slow the ground speed of the sprayer. Again, for changes more than 25 percent, change the nozzle tip size.

Example: Sprayer output is 34 GPA. You want to apply 22 GPA. 34 - 22 = 12. 12/34=35 percent change. You will have to replace the nozzle tips with a smaller size to get the desired rate in GPA. You cannot adjust the pressure or the ground speed enough with minor changes to get the desired application rate.

To calibrate a sprayer for band application of chemicals, determine the band width to be sprayed in inches and convert to feet. Example: band width is 8 inches. 8/12=0.6666 feet. 340/.666= 510 feet

The calibration course length will be 510 feet. Proceed to calibrate by following the above instructions for broadcast calibration. The rate of application for banding will be the amount sprayed on the banded area only, not the total acreage driven over. For example, if you are banding an 8 inch band on 24 inch rows, the area sprayed for each acre driven over will be only one-third of an acre ( 8/24 or 1/3).

To calibrate a sprayer for applications with more than one nozzle per row, determine the row spacing in feet. Divide 340 by the row spacing in feet. For example, 60 inch rows on a 5 foot spacing (60/12=5). 340/5= 68 feet. The length of the calibration course will be 68 feet. Proceed to calibrate following the instructions for broadcast calibration. To determine the application rate in gallons per acre for multiple nozzles, catch the output from all nozzles for one row and add the total catch for one row to get the gallon per acre application rate. For example, if you have 8 nozzles per row and each nozzle is spraying 6 ounces for the calibration period, the application rate is (6 x 8) 48 gallons per acre.

Most of the 48 gallons applied to each acre will be water used as a carrier or diluent for the active chemical being applied. That is, if you are applying one pint of ridomil to the acre at a rate of 48 gallons per acre, you will have a tank mixture of one pint of ridomil and 47 gallons and three pints of water mixed with the ridomil to give a total of 48 gallons.

Sprayer wear and deterioration are a normal occurrence with sprayer use. However, misuse can easily shorten the useful life of sprayer equipment. The following suggestions will help prolong the life of your spray equipment.

Pesticide applicators should make every effort to reduce drift from their spraying operations. Excessive spray drift can lead to adverse publicity about agricultural chemicals. The overall effect of this adverse publicity can be determined to the production of food and fiber possibly resulting in some pesticide product withdrawals form the market. Applicators should be responsible individuals with enough respect for the environment to make every effort to utilize chemicals properly.

Pesticides can drift as far as one-half mile away from the target area if application methods and wind conditions are not ideal. Sensitive vegetation in the drift area can be severely damaged or destroyed depending on the chemical type used. Not only is off-site vegetation damaged - often with resulting adverse publicity - but chemical is wasted and ineffective pest control can result. Additional applications of pesticides may then be required to control pests with corresponding additional expenses.

Fortunately, there are several effective methods for reducing spray drift from agricultural chemicals. Ten ways in which pesticide drift can be reduced or eliminated are:

2. Use a lower spraying pressure whenever possible.

3. Lower the boom height or use drop nozzles to reduce wind effects.

5. Use drift shields when possible,

6. Don’t spray when the wind is above 7-10 miles an hour.

7. Use a drift control additive.

9. Don’t spray during the times of air inversions.

10. Leave a buffer zone between sprayed crops and chemical-sensitive crops.

Using larger nozzle tips, raindrop or full-cone tips and lower spraying pressures results in larger droplet sizes that are less affected by wind than are smaller droplet sizes. Lowering the boom height reduces the distance the spry droplet has to travel to the target, thus reducing the effects of wind on the droplet. Be sure to maintain enough boom height to insure uniform application of the chemicals. When possible, adding more water to the spray mixture allows you to use larger tips which produce larger droplet sizes.

Air inversions often occur in the morning as land begins to warm up quickly from the rising sun, especially around hilly terrain. Inversions are also likely to occur around bodies of water such as lakes or streams, Inversions tend to lift small droplets into the air rather than letting then fall onto the target area.

Sprayer shields are commercially available for most sprayers. Shields can also be constructed rather simply and inexpensively if commercial brands are not readily available in you area. Additives for spray solutions to eliminate or greatly reduce drift are available in your area. Costs for additives vary, but are usually less than a dollar an acre.

Reduce or eliminating spray drift can be profitable to spray applicators. Not only does more spray reach the intended target, but the environment is not adversely impacted and relations with neighbors are not strained.

For additional information on sprayer calibration or sprayer design, see The University of Tennessee Agricultural Extension Service publications PB 1535 "Agricultural Chemical Sprayer Facts", PB 1276 "A Guide to Proper Sprayer Calibration" and PB 1233 "Sprayer Nozzle Tip Capacity Information" or contact your local State Agricultural Extension Service.

Mailing address for the authors: Ellington Agricultural Center, 5201 Marchant Drive, Nashville, TN 37211-5112.

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