This article contains information that will assist you in becoming more proficient in the area of application technology in a manner that is both easy to understand and immediately useful.

In turn, this will allow you to create high-performing applications that are also secure, efficient, and environmentally friendly.

Drift control measures

Spray boom height

The lower the spray boom is to the crop or target, the less opportunity the wind, airflow, and other weather factors have to move droplets from the intended target. But remember that a boom height lower than the spray tip manufacturer’s recommendation results in an uneven application. So, before adjusting the sprayer boom height, make sure you are following the spray tip manufacturer’s recommendations.

Spray boom stability

The movement of a spray boom without stability can result in:

• Greater drift risk when the boom is working at a higher spray height

• Uneven distribution along the treated area Therefore, sprayers equipped with a spray boom with great stability provide a uniform application and have better control of spray drift.

Spray tips for drift reduction

Drift potential can be minimised by using low-drift spray tips. Low drift spray tips feature two mechanisms to produce coarser droplets and fewer driftable fines (droplets with a diameter smaller than 150 μm): pre-orifice and/ or venturi air induction technology.

Pre-orifice flat fan spray tips

Pre-orifice spray tips reduce the operating pressure internally and produce larger droplets than conventional flat fan spray tips. The tip’s pre-orifice restricts the amount of liquid entering the tip and creates a pressure drop through the tip. Fewer droplets prone to drift are produced creating excellent spray pattern uniformity. The examples of TeeJet® Technologies’ low drift spray tips with a pre-orifice design are DG, TT, and TTJ60.

Venturi air induction spray tips

Air induction spray tips have two orifices. The first orifice, known as the pre-orifice, meters the liquid. The second orifice, known as the exit orifice, is larger than the pre-orifice and is responsible for forming the spray pattern. A venturi system or air aspirator sits between the two orifices. This venturi system draws air into the body of the tip, where it is mixed with water.

This mixing creates an air-entrained spray pattern at a lower pressure. The spray pattern is comprised of large, air-filled, coarse droplets with very few drift susceptible droplets. The examples of TeeJet® Technologies’ air induction tips are AI, AIXR, AITTJ60, TTI60, and TTI. The graphic below represents the volumetric median diameter (VMD) of the TXA, XR, TT, TTJ60, AIXR, and TTI spray tips with the same capacity of 0,4 GPM (1,52 ℓ/min) operating at 40 psi (2,8 bar). The TXA spray tip produces the smaller droplets.

To choose the ideal low-drift spray tip for a safer application, it is also important to evaluate the percentage of driftable fines produced by each spray tip type, as shown in the table below.

Based on the driftable fine data from the previous table and using a computational fluid dynamics (CFD) technique, it is possible to create a simulation where we can observe the driftable potential plume of different spray tips – XR, TT, TTJ60, AITXA, AI, AITTJ60, TTI60, TTI, from the left to the right respectively (image below).

The simulation was carried out by comparing the spraying of all spray tips with the same capacity of 0,4 GPM at 40 psi (1,52 ℓ/min at 2,8 bar), with a wind speed of 10 mph (17 km/h).

Operating pressure

The reduction of the operating pressure can be used as a measure to mitigate drift, as shown in the table below. However, if just by reducing the operating pressure the percentage of driftable fines are still above the limit for a safe application, the user must select a spray tip that produces coarser droplets with a lower percentage of driftable fines.

Weather conditions

In order to make the best application decisions to minimise spray drift, the applicator must be aware that weather varies throughout the day. Therefore, it is important to check the wind speed, temperature, and relative humidity before and during the spray application. Thus, the wind speed measurement must be carried out at least at the beginning of spraying and at each tank refilling, using a weather meter to check if the application is taking place within the recommended wind speed range.

Drift reduction agents (DRAs)

The most critical factor in reducing spray drift is selecting a spray tip that produces the proper droplet size. The addition of drift reduction agents (DRAs) to the tank mixture can reduce driftable fines, but will never substitute the use of the right tip for drift mitigation. DRAs’ role is to assist the embedded technology in the spray tip. Pay attention to the spray angle when using DRAs – a more viscous solution can reduce the spray angle.

Buffer zone

A buffer zone is an area not treated with crop protection products, located between the target area and a sensitive area, such as:

• Sensitive crops

• Water source

• Urban areas

European regulations for drift reduction

Many European countries evaluate spray nozzles/tips for drift reduction. This makes general cooperation among agriculture, nature conservation, and environmental protection possible. The use of low drift tips brings significant benefits to users in the United Kingdom, Netherlands, and Germany, as well as others around the world. Stricter requirements for buffer zones to protect surface water and sensitive areas around fields have led to the development of a programme that assesses spray tip drift control as well as innovative tips producing larger droplet sizes.

Depending on the location of the fields relative to environmentally sensitive areas, such as surface water and field boundaries, applicators must use specific low drift spray tips and manage the width of buffer zones. TeeJet® Technologies features many spray tips designed to reduce drift that are tested and certified in each of these European countries, ensuring an effective and safer application.

The assessment is based on drift control using a reference system based on a tip specified by ISO 25358 droplet size classification. All approved and certified TeeJet spray tips are on our website: www.teejet.com.

In Germany, the Julius Kuhn Institute – Federal Research Institute for Cultivated Plants (JKI) is responsible for testing spray tips for agricultural use. In the United Kingdom the tests are carried out by LERAP, in France by INRAE, and in the Netherlands by DRD.