Cooperative Extension Service The University of Georgia College of Agricultural and Environmental Sciences

SOYBEAN SPRAYER APPLICATION AND NOZZLE SELECTION
Paul E. Sumner, Extension Engineer

Nozzle section is one of the most important decisions to be made related to pesticide applications. The type of nozzle determines not only the amount of spray applied, but also the uniformity of the applied spray, the coverage obtained on the sprayed surfaces, and the amount of drift that can occur. Each nozzle type has specific characteristics and capabilities and is designed for use under certain application conditions. The types which are commonly used for ground application of agricultural chemicals for soybeans are the fan and cone nozzles.

Herbicide Application

The type of nozzle used for soil incorporation and applying herbicides is one that develops a large droplet and has no drift. The nozzles used for broadcast applications include the regular flat fan, extended range flat fan, drift reduction flat fan, turbo flat fan, twin flat fan, Air-assist flat fan, flood and wide angle cone nozzles. Operating pressures should be 20 to 30 psi. Pressure over 40 psi create significant drift. These nozzles will achieve uniform application of the chemical if they are placed properly along the boom. For the flat fan nozzles overlap should be 50 to 60 percent. Wide angle cone and flood nozzles should have 100 percent overlap. Table 1 presents suggested boom heights for flat fan nozzles with different angles. Also the orientation of each along the boom should place such they are angled 5 degrees from the center line of the boom.

Table 1. Various nozzle heights for a 20 inch spacing.

Even flat-fan nozzles are used for banding herbicides over the row to apply uniform coverage across the entire width of the spray pattern. The width of the band produced is determined by nozzle height (Table 2).

Table 2. Nozzle height for 80 and 95 degree even flat fan nozzles in inches.

Insecticide and Fungicide Applications

Hollow cone nozzles are used primarily when plant foliage penetration is essential for effective insect or disease control, and when drift is not a major concern. At pressures of 40 to 80 psi, these nozzles produce small droplets that readily penetrate plant canopies and cover the underside of the leaves more effectively than any other nozzle type. The hollow-cone nozzles produces a cone-shaped pattern with the spray concentrated in a ring around the outer edge of the pattern. Even fan and hollow cone nozzles can be used for banding insecticide an fungicides over the row.

Nozzle Material

Various types of nozzle bodies and caps, including color coded versions, and multiple nozzle bodies are available with threads as well as quick-attaching adapters. Nozzle tips are interchangeable in the nozzle cap and are available in a wide variety of materials, including hardened stainless steel, stainless steel, brass, ceramic, and various types of plastic. Hardened stainless steel and ceramic are the most wear-resistant materials but are also the most expensive. Stainless steel tips, with corrosive or abrasive materials, have excellent wear resistance. Plastic tips are resistant to corrosion and abrasion and are proving to be very economical for applying pesticides. Brass tips have been common but wear rapidly when used to apply abrasive materials such as wettable powders and are corroded by some liquid fertilizers. Brass tips are economical for limited use, but other types should be considered for more extensive use.

Table 2 is a chart that can be used as a guide for selecting the proper nozzle type for most soybean spraying applications.Table 3. Suggested application for various spray nozzles used in soybeans. 1 - Excellent, 2 - Very Good, and 3 - Good.

* Example of nomeclature for nozzles.

Selecting The Proper Size Nozzle Tip

The correct nozzle tip size will depend upon application rate in gallons per acre (GPA), ground speed (MPH), Effective spray width of each nozzle (W). The best method for choosing the correct nozzle tip size is to determine the gallons per minute (GPM) of nozzle output required and then select a nozzle tip size that, when operated within the recommended pressure range, will provide this flow rate. Avoid relying on the "gallons per acre" rating which some manufacturers give their nozzles as means of selecting nozzle tip size. This rating is correct only for standard conditions (usually 30 psi, 4 MPH, and 20-inch nozzle spacings). The gallons-per-acre rating is useless if any vary from the standard. By following the steps described below, the proper nozzle tip size can be selected well ahead of the spraying season.

1. Determine "GPA " - First select the application rate in gallons per acre (GPA) used. The application rate consists of the gallons of carrier (water, fertilizer, etc.) plus chemical applied per treated acre. The best guides for this decision are the recommended ranges listed on the label, the recommendation of a chemical dealer or county agricultural agent, and experience with that particular chemical.

2. Determine "MPH" - Select an appropriate ground speed in miles per hour (MPH) for the field to be sprayed. Experience is the best guide here. Generally, speeds between three to 7 MPH are considered appropriate for low pressure ground sprayers depending upon field conditions. Do not rely solely on speedometers as an accurate measure of ground speed, especially on older tractors. Slippage and variation in tire sizes can result in speedometer errors of 30 percent or more. Ground speed can be determined by the following equation:

3. Determine "W" - Determine the effective sprayed width per nozzle (W) in inches.
For broadcast spraying, W = nozzle spacing, For band spraying, W = band width, For row-crop application, W = row spacing (or band width).

4. Determine Tip Size - Once the application rate, ground speed, and spray width per nozzle have been determined, the flow rate required for each nozzle in gallons per minute (GPM) can be determined by using a nozzle catalog, tables or the following equation:

The constant, 5,940, is used to convert gallons per minute, miles per hour, and inches to gallons per acre. The use of 6,000 instead of 5,940 will make the calculation easier and result in an error of only one percent.

Example: A herbicide is to be broadcast at 20 GPA at a speed of 5 MPH, using flat fan nozzles spaced 20 inches apart on the boom. What size nozzle tip should be selected?

The required flow rate for each nozzle is as follows:

The nozzle selected must have a flow rate of 0.34 GPM when operated within the recommended pressure range of a flat-fan nozzle (20 to 30 psi). By checking nozzle catalogs, you will find a number of different brands of flooding flat fan nozzles which will provide this flow rate. For example, the Spraying Systems XR8004 and Delavan LFR80-4R nozzles have a rated output of 0.35 GPM at 30 psi. Either of these nozzles will be sufficient for this application.

Example: A foilier fungicide is to applied at 15 GPA at a speed of 7 MPH, using hollow cone nozzles. The row spacing is 36 inches with three nozzles directed toward each row. What size tip should be selected?

The required flow rate for each row is as follows:

The flow rate for each nozzle is the row (GPM) divided by the number of tips per row.

The nozzle selected must have a flow rate of 0.21 GPM operating between 40 to 80 psi. Checking nozzle catalogs, the Spray Systems TX-10 and Delavan HC-10 cone spray nozzles have a rated output of 0.20 GPM at 60 psi. Or the Spray System D 4-23 and Delavan DC 4-23 disc-core nozzles have a rated output of 0.21 GPM at 80 psi. Either one of the nozzles chosen would deliver the proper amount per acre.

Water Rates (GPA)

The grower who plans to use spray materials at the low water rates should follow all recommendations carefully. Use product label recommendations on water rates to achieve optimal performance. Plant size and condition influence the water rate applied per acre. Examination of the crop behind the sprayer before the spray dries will give a good indication of coverage.

Agitation

Most materials applied by a sprayer are in a mixture or suspension. Uniform application requires a homogeneous solution provided by proper agitation (mixing). The agitation may be produced by jet agitators, volume boosters (sometimes referred to as hydraulic agitators), and mechanical agitators. These can be purchased separately and installed on sprayers. Continuous agitation is needed when applying pesticides that tend to settle out, even when moving from field to field or when stopping for a few minutes.

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, The University of Georgia College of Agriculture and the U. S. Department of Agriculture cooperating.
Gale A. Buchanan, Dean and Director

05/27/99