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Quality accessories for sprayers

The equipment for spraying operations must comply with specific Community directives, which set binding requirements for manufacturing companies, and must be subject to periodic inspections under the National Action Plan as an obligation for users. The industry has developed a wide range of technological solutions that optimize treatments and dramatically reduce environmental impact

by Davide Facchinetti
October - November 2016 | Back

The equipment for spraying operations must comply with specific Community directives, which set binding requirements for manufacturing companies, and must be subject to periodic inspections under the National Action Plan as an obligation for users. The industry has developed a wide range of technological solutions that optimize treatments and dramatically reduce environmental impact

The increasing attention paid by public opinion to pollution from the field spraying of pesticides initiated the enactment by the European Community of Directives 2009/127/EC and 2009/128/EC, later transposed in Italy. The first was an amendment of the machinery Directive, while the second was transposed recently with the adoption of the PAN (National Action Plan). This legislative document essentially sets new constraints on end users. For example, it sets forth the obligation to submit to periodic functional inspections, at specialized centres, nearly all machines used professionally for the distribution of pesticides (only some types of small machines carried by hand or shoulder by the operator escape this rule).

It is important to know that carrying out the mandatory functional inspection, when combined with a simultaneous calibration of the machine by skilled technicians using special test benches, significantly improves the performance of the machine in its different contexts of use. This is because it is almost always possible to make a specific machine adjustment that will improve its performance, both from the point of view of maximizing the percentage of sprayed product that can be effectively deposited on the leaf, and from the point of view of minimizing any product being unnecessarily released into the environment. This “machine calibration” is performed by checking some simple variables, such as the orientation and size of the nozzles, the settings relating to the range, the range of the pumps, the rotation speed of the fans, and the adjustment of any of the air deflectors.

Directive 127, which aims to ensure the environmental sustainability of factory-new sprayers (and concerns the manufacturers firsthand) was implemented in our country on 17 April 2012. From that date, to be able to market their machines, manufacturers must comply with a set of minimum requirements that have the purpose of limiting unwanted accidental scattering of product into the environment, both in the distribution phase and in the prior stage of preparation of the mixture to be distributed. In summary, Directive 127 requires manufacturers to put on the market only machines that have a technical dossier. In addition to including the self-certification on the safety of the machine to be able to give it a CE marking, the dossier must include the aforementioned aspects related to the operator’s safety, as well as those pertaining to environmental protection.

All these obligations are also extended to small equipment carried by the operator, even if operated by hand, if it has a tank with a capacity exceeding 4 litres. Compared to the machines sold prior to 17 April 2012, the latest may be marketed only if designed and constructed to facilitate cleaning, in particular that of the main tank. This can be ensured by providing a special machine washer tank and the related circuit.

Furthermore, the manufacturer must now provide much more complete use and maintenance manuals, which must include information such as to provide the operator with the ability to perform the most common machine adjustments, in order to adapt it for use in different conditions or on different types of systems. Furthermore, the manufacturer must supply the machine with mandatory accessories such as a calibration kit (or at least a jug with a minimum capacity of 1 litre, graduated at intervals of not less than 20 ml and precision not less than 2.5%) and a possible adapter for connecting it to a flow meter, to measure the pump flow rate during the periodic functional checks.

In response to the growing need for increasingly environmentally friendly pesticide treatments, the sprayers developed in recent years have proved able to considerably reduce the volumes of products used for crop protection. This result was obtained by using devices of a different type such as tunnel atomizers, equipped with devices to recover and reuse product that did not reach its target, or electrostatic devices that help the active ingredient to stick to the target vegetation, or spraying bars with air sleeves.

The next step in the evolution of sprayers, correlated to the development of precision agriculture, would be to enable “precision protection”. Not surprisingly, there is a lot of research aimed at developing new, increasingly “smart” sprayers, able to autonomously adapt the dose of dispensed product based on parameters such as: the distance, thickness, and extent of the target vegetation, as well as any presence of certain pathogens, using machines with variable rate technology (VRT). From this point of view, the scientific research is making great strides, and the first commercial applications are expected in the coming years.

Essentially thanks to legislation 127 and to the general technological progress, the minimum requirements of new machines have in fact increased, but much more can be done to improve functionality, given the ecological problems associated with the use of these machines. There are many devices, electronic or otherwise, that can be installed on the machines even in the aftermarket, able to further improve their performance, not only from the point of view of environmental protection, but also from that of phytoiatric effectiveness of the treatment.


Technologically advanced accessories

Electronic control units and speed, pressure, and flow rate sensors. For many years now, we have seen DPA sprayers (acronym for Directly Proportional to Advancing speed) capable of automatically adjusting the operating pressure based on the speed of advance, in order to maintain constant and at the desired level the amount of mixture distributed per surface unit. These machines help avoid underdosing and overdosing, even when you cannot maintain a constant speed during the treatment.  The electronic control units of the machines in question exploit simultaneously sensors able to provide the advancing speed and sensors that provide the nozzle supply pressure, and possibly also the actual flow rate they deliver. Lately, these small on-board computers can do even more, thanks to the fact that they can interface with the recent satellite georeferencing devices. For example, these allow modern spraying bars to automatically close the supply based on their position in the field, without the operator’s input. All this avoids harmful treatment overlaps and the unnecessary distribution of mixture outside the target field. In this case these are not variable rate techniques, but “on-off” solutions, which still greatly increase the efficiency of the treatments.

Anti-drift nozzles. These come in various types, and by now they are also included in some standard configurations. These special nozzles dramatically decrease the drift effect when installed on spraying bars, while their effect is still positive, but much less noticeable when used on atomizers. Given the production of larger droplets, compared to traditional nozzles of equal calibre, these nozzles should be assessed carefully when there is a need for accurate and continuous coverage of the target, as in the case of covering or contact product treatments. In these cases, to maintain the desired phytoiatric effectiveness, in most cases it is best to adequately increase the volume of water being distributed.

Ultrasonic sensors. These sensors emit a sound wave at a very high frequency (ultrasonic), and by measuring the reflected wave (i.e. the echo) they are able to assess the distance between the emission source and the hit target. For example, by mounting them on atomizers, these devices can measure the presence and thickness of the foliar surface to be treated, and then allow a variable rate distribution (commercial applications relating to this technology are still not available on a large scale). When they are mounted on the ends of the spraying bars, they allow an electronic control unit to use the received signals to drive a pair of hydraulic pistons. These maintain the spraying bar always at the correct distance from the ground, be it ridged or, as is often the case, characterized by asperities that could affect the dynamic stability of the bar. It is also possible to obtain similar results fitting the spraying bars with some simple spring probes connected to a microswitch, instead of the above-mentioned ultrasonic sensors. Unlike what was said about atomizers, in the case of spraying bars these technologies are already available on the market.

Multispectral optical sensors. These sensors, when mounted on drones or, in some cases, even on satellites, can employ remote sensing techniques to obtain NDVI maps (normalized vegetative vigour index), which can be used to adjust the variable rate sprayers. The vegetative vigour maps can also be obtained with devices that run along the rows on the ground, either by mounting these sensors on vehicles that precede the machine for the treatments, or by mounting them on the sprayer itself, taking care to place them far enough ahead of the device spraying the phytoiatric mixture. For example, the Swiss company Avidor hightech produces a device that adjusts the flow of liquid sprayed by the atomizers based on the information given by the NDVI index derived from the maps. The optical sensors such as the Green-seeker or weed-seeker, when mounted on spraying bars intended for inter-row weeding in hoed crops or on-row weeding in vineyards or orchards, can automatically open the nozzles solely in the presence of weed vegetation, avoiding the unnecessary spraying of bare soil.

Electrostatic charging of ejected liquid particles. These devices electrically charge the phytoiatric mixture droplets with an opposite charge from that of the target vegetation. This promotes an increase in pesticide deposits, thus reducing the droplets dispersed in the environment unnecessarily due to drift. Among other things, this phenomenon involves a better spatial distribution of the particles due to the mutual repulsion between identical charges. The force of electrostatic attraction to the vegetation is often higher than gravity itself, thus favouring an increase in the deposit on the undersides of leaves. Although some always recommend the use of these devices, in order to reduce by up to 20% the doses normally used in pesticide treatments, others advise against their use with products that act by contact or coverage. Given that the electrostatically charged droplets are less likely to penetrate into the middle of a bunch of grapes or a very thick and dense vegetation, the use of these devices always implies an increase of deposits on the periphery of this type of vegetation, at the expense of the deposits in the central areas.

Spraying bars with air sleeves: although transporting the droplets ejected from the machine by specific air flow towards the target vegetation has now been the practice for decades in the field of tree crops, this method was introduced for herbaceous crops only recently. In the latter case, the air current serves both to improve the penetration of the treatment within imposing vegetated masses, and to decrease the occurrence of drift problems. All this allows the safe performance of treatments even in the presence of modest environmental air currents. These machines produce a current of air at a rate of 25-35 m/s, carrying downward the liquid ejected from the nozzles, and also “opening” the underlying vegetation to better penetrate the droplets within them. The implementation of an air sleeve to a spraying bar that originally did not have one is a modification that cannot be counted among the “inexpensive” ones. Nonetheless, such an addition can still be done fruitfully in aftermarket to considerably improve the distribution efficiency of these machines, allowing subsequent savings in terms of pesticides.


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