Nozzles should hit the spot


With chemical costs being the biggest share of variable cost expenditure for arable farmers, it is important that the stuff is applied to the target and at the right time. Timeliness, to some degree, is driven by sprayer output and boom design is crucial to the performance of the sprayer with good contour following and stability paramount to maintaining the correct height above crop.

All boom movement is created by the towing vehicle and so sudden acceleration or deceleration, rocking back and forth across ruts or working across slopes will all have a major impact on nozzle height. The least influenced the boom is by the vehicle, the more stable it inherently is. Of course, all sprayer booms have a suspension system to provide lateral and longitudinal guidance to the boom and the effectiveness of these systems is crucial to performance and thus on any limiting of potential forward speed. The better the boom ride is, then more output with the sprayer is possible and the easiest way of making the best use of those few spraying days is to be able to spray more acres a day. Heavier booms have more momentum, especially those with more weight in the boom tip and this helps to create yaw.  Yaw movement is potentially the worst action for a sprayer boom as the frequency in which the boom travels backwards and forwards leads to multiple overspray at the boom tips. Watch the end of your sprayer boom as it passes you by - is it going to and fro? If so, it is costing you money. Boom roll and bounce are normally easier to dampen with a mixture of springs, accumulators and shockers, but here, speed of reaction is the main yardstick in making sure the boom gets back on target as soon as possible after being disturbed.

Tilt systems and variable geometry make it possible for the operator to steer the boom from left to right, or lift and lower the boom tips, but this is reactive and not proactive adjustment and so the workload this places on the operator leads to a reduction in travelling speed to be able to maintain the optimum boom position. The result? Less output per day. Also, the more they are concentrating on the boom height means they are not able to focus on the fundaments of spraying and so the temptation is to run with the boom higher than the optimum to play it safe. But however, this leads to a negative effect on drift.  Electronic height systems, such as Amazone’s DistanceControl, are an aid to reducing the stress on the driver by automatically maintaining the correct height above crop. However, the system needs to be more than just a few ultra-sound sensors fitted afterwards and the system should be integrated into the boom design to get the best contour following without a compromise on reaction time or poor guidance. Wider widths increase the need for variable geometry boom and automatic height control becomes a ‘must-have’ option.

And above all, don’t forget the basics; for a 50cm nozzle spacing on the boom and a 110° fan, the target running height is 50cm above crop, is your sprayer even capable of spraying down as low as this when pre-emergence or stubble spraying? Increasing the boom height by just 20cm above that target will double the amount of spray drift and thus be costly in terms of both the efficacy of application and to the environment. Applying chemical to a target is a sprayers’ only aim and the ability to maintain the nozzle position to the target is only as good as its boom ride.