Obvious parameters for application efficiency, and easy wins, are spray volume and nozzle choice. Syngenta application specialist Tom Robinson assesses the issues.

Why efficient spraying?

Having looked in the previous Academies at the impact of boom set-up, filling operations and forward speed, in this final instalment we look at some of the more obvious parameters for application efficiency - spray water volume and nozzle choice.

Clearly, spraying at reduced water volumes is not possible with all products and must only be carried out where it is permitted by the timing, target, nozzle choice and spray pressure. Careful consideration should be given before reducing water volumes.

But, where possible, lower water volumes are a very efficient way to go spraying.

Video: Sprayer water volume & nozzle choice

Approved product

If you reduce the water volume from 200 to 100 litres/ha (with a label-approved product), then straight away you have doubled the capacity of your sprayer.

Using the example in the table - for a 2500-litre sprayer operating at 12kph and taking into account time for filling, travelling, etc - this reduction would allow an extra 23ha a day to be treated at the lower volume.

If you had to hire a contractor to spray those 23ha to catch up, based on a contract spraying cost of £10/ha, that would equate to about £230.

In addition, studies have shown that if a T2 fungicide is delayed, then yield can fall by 70kg/ha a day, or the equivalent of about 0.5t a week.

Assuming a grain price of £80/t, over 23ha the 70kg reduction would equate to a £128 a day loss. Therefore, these two factors could make a difference of more than £350.

A further advantage of lower water volume spraying is that some products can actually work better, enabling you to achieve a biological improvement as well.

Appropriate nozzles

Alongside reducing water volumes, appropriate nozzle choice can also boost efficiency. Fitting the right nozzles for the job brings benefits in three ways:

• Reduced drift - as with boom height, correct nozzles can minimise drift and, therefore, open up more spraying opportunities. Air induction nozzles are particularly good at reducing drift, but are not widely used.
• Increased workrates - by allowing more hectares to be sprayed a day (linked, where possible, to reduced water volumes and faster forward speeds).
• Improved product performance - by getting more spray on the target and from more timely spraying (again from work rates and making best use of spray windows).

Typically, a standard nozzle fitted to sprayers is a variable pressure 110° -05 flat fan nozzle. It will produce a medium quality spray at 200 litres/ha and, by and large, will do a good job. But its performance can often be improved.

Often, they are used at too high a pressure. But they produce less drift at 2 bars than at the more traditional 3 bars. So when choosing a new set of standard nozzles, calculate the correct output at about 2 bars pressure rather than 3 bars and you could extend spraying opportunities by reducing drift.

Specialist nozzles

Specialist nozzles, although perhaps costing more, can offer advantages.

When choosing nozzles, a key aim is to get maximum spray on to the target and minimise the amount wasted.

For spring and summer use, the Amistar Nozzle is a very low-drift nozzle, with a 3-star LERAP rating. It was developed specifically for spraying cereals in particular, at the ear or T3 timing, where its angled tip has been specially designed to produce even coverage on both sides of the ear or plant as the sprayer passes over. Its benefits include more spray days with a quarter of the amount of drift, and it has produced about 0.3t more yield when used to apply the same fungicide mix.

Low drift

The Amistar nozzle also produces lots of droplets per litre, and has been shown through trials to be as effective for spring grassweed control. It has been found to deposit 30% more spray on a wild oat target than an alternative nozzle. Therefore, new for the 2007 season, it is the preferred nozzle for Axial (pinoxaden) where it is permitted to be used in 100 litres/ha spray volume because it:

• Deposits more spray on wild oats.
• Utilises air induction principles. to cut spray drift and, therefore, increases available spray days.
• Allows faster work rates from a 100 litres/ha spray volume (where this is permitted).

Autumn nozzle

Similarly for autumn, the 40° forward-angled Hawk nozzle has been shown to deposit more than double the amount of spray compared with a vertical nozzle on small blackgrass plants, which are a notoriously difficult spray target to hit. This should achieve better blackgrass control and give higher yields.

Meanwhile, for a pre-emergence herbicide application, where bare soil is the target, using alternating fore- and backward-facing Hawk nozzles along the length of the boom evens out coverage on both sides of clods.

The Hawk nozzle is also designed for a 100-litre/ha spray volume, for faster work rates and to make maximum use of spray windows.

In summary, choosing the right nozzle for the job can produce better control (for example, grass weeds), give higher yields and improved work rates from more spray days.