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Spray booms, innovations that reduce pesticides

Limiting the use of pesticides is essential to protect the environment and human health. Technological innovations in the agro-mechanical field can make a fundamental contribution in this regard, optimising and rationalising the use of plant protection products

by Davide Facchinetti
February 2024 | Back

Modern agriculture faces the crucial challenge of reducing the use of pesticides to preserve the environment and human health, and all this must be achieved without compromising the yield and quality of the crops. Despite the fact that the Agriculture Committee of the European Parliament has recently cancelled, following the widespread protest of farmers, the measure that provided for a halving of the use of pesticides by 2030, it is still advantageous for farms to focus on the reduction of chemicals in agriculture, thus supporting increasingly widespread consumption styles, in Europe and beyond. It should also be noted that the EU Commission, by requesting the halving of the quantity of pesticides used in agriculture, did not propose any alternative solution, thus putting in serious difficulty the Community agricultural productions which for various reasons already find themselves dealing with problems of self-sufficiency (i.e. the need to import from areas outside the borders of the EU), as well as a continuous and constant increase in production costs due to a succession of increasingly restrictive legislation (including on engine emissions). Especially since the targets set by Brussels would have required farms to invest heavily in new agricultural machinery and technology.

Pesticides and Assisted Evolution Techniques. A big help to rationalisation and efficiency in the use of pesticides will also come from the use of TEAs (acronym for Assisted Evolution Techniques), the biotechnologies now defined as ‘sustainable’ especially by those who have finally realised that boycotting the use of GMOs has done nothing but further reduce the competitiveness of European and Italian agriculture in particular (given that in some EU countries many GMOs are in fact cultivated). With these new techniques of ‘genome editing’ and cisgenesis, we are always making changes to the genetic heritage of plants, but in a different way than the technologies known as transgenesis, i.e. those that lead to the obtaining of GMOs. Although similar results are obtained, the plants obtained by genome editing do not contain any DNA of external origin, but only a mutation, i.e. no one will ever be able to prove a posteriori the origin of the mutation itself, whether it is of natural, chemical or biotechnological origin. It also follows that changes made to the genetic heritage of plants by means of cisgenesis or transgenesis techniques are not subsequently identifiable.

Reduction of pesticides, the contribution of electronics. However, further help to reduce the use of pesticides can also come from the use of technologically advanced solutions on operating machines, which in the case of open field crops are represented by spray booms. Modern DPA control units (acronym for Directly Proportional to Advance) equipped with speed, pressure and flow sensors, have been marketed for many years now to automatically adjust the operating pressure (and therefore the amount of flow supplied) according to the forward speed, in order to keep the quantity of mixture distributed per unit area constant and at the desired level. With these machines it is therefore possible to avoid under-dosing and over-dosing even when it is not possible to keep the speed at which the treatment is being carried out constant. The electronic control units of the machines in question use both sensors capable of detecting the forward speed and sensors that allow them to know the supply pressure of the nozzles and often also the flow rate actually delivered by them.

Air hose: a simple but reliable technology. Among the various technologically advanced accessories that can assist the function of spray booms, the air hose is the one that has been on the market for the longest time and probably also the one that exploits the simplest and most consolidated technologies, however it is still an accessory that is not very common on the fleet of machines sold as new, and even more so on those in use in the area. One of the main challenges in the application of pesticides is spray drift, i.e. the dispersion of pesticide particles into the surrounding environment. The use of the air hose significantly reduces this phenomenon, directing pesticides directly and specifically to crops and minimizing contact with surrounding non-target areas. This not only protects the environment and biodiversity, but also reduces the risk of human exposure to pesticides. In addition, the use of the air hose allows for more uniform coverage on crops, ensuring that pesticides reach even the deepest parts of the vegetation effectively. This targeted approach improves the effectiveness of phytosanitary treatment, maximizing the control of diseases and harmful insects when they nest in the deepest parts of vegetation. Thanks to fans usually driven by a hydraulic motor, the hoses in question produce an air current at a speed of 25-35 m/s, which transports the liquid ejected from the nozzles downwards and also allows the underlying vegetation to be "opened" so that the droplets can better penetrate inside it. The implementation of an air hose with a spray boom, which originally did not have one, is a modification that is not to be counted among the "cheap" ones, even if this addition can still be profitably carried out in the after-market to significantly improve the distribution efficiency of these machines, allowing subsequent savings in terms of plant protection products. The use of the air hose therefore contributes to the sustainability of agricultural practices, improves the efficiency of the application of pesticides and, by reducing waste and operating costs, also increases the profitability of agricultural activities.

Electrostatic charge to reduce drift. Electrostatic charging is a technology that improves the adhesion of pesticides to plant surfaces on spray booms and thus reduces waste during application. This system exploits the creation of an electrical potential difference between the spray boom and the plants, generating an attractive force that facilitates the adhesion of pesticide particles to the leaves and stems of crops. These devices basically give the droplets of phytoiatric mixture a charge opposite to that of the target vegetation, to encourage an increase in useful deposits on it to the detriment of the droplets unnecessarily dispersed in the environment by drift. Electrostatic charging involves, among other things, a better spatial distribution of particles due to the reciprocal repulsion that occurs between identical charges. Often the electrostatic force of attraction towards the vegetation is also greater than the gravitational one, thus favouring an increase in the deposit on the underside of the leaves. Although some always propose the use of these devices, in order to reduce the doses normally used in pesticide treatments by up to 20%, others do not recommend their use with contact products or for cover products, considering that electrostatically charged droplets are less likely to be able to penetrate deeply into very dense and thick vegetation. In fact, the use of this technology always leads to an increase in the deposit on the peripheral part of this type of vegetation, to the detriment of the deposit in the central areas.

Georeferencing and automatic closure of nozzles. The use of tractors equipped with automatic guidance systems connected to spray booms equipped with solenoid valves that automate the opening and closing of the flow to the sections, or even to the individual nozzles, represents another key innovation in spray booms. In fact, one of the main challenges in the distribution of plant protection products in the open field is the need to avoid overlaps and gaps, while ensuring complete coverage of the field. Thanks to these solutions, this problem is solved effectively and with extreme precision, allowing operators to activate and deactivate specific sections of the spray boom (or individual nozzles) based on the information coming from an electronic control unit that exploits satellite georeferencing to map exactly the areas where the product is distributed. The application of pesticides is therefore carried out in a targeted manner, avoiding treating unnecessary or already treated areas. Not only does this reduce product waste, but it also helps to preserve biodiversity and minimise the exposure of soils and water resources to potentially harmful chemicals.

Use of special nozzles for greater drift containment. In the application of pesticides, in addition to the classic "fan" nozzles, it is also possible to find specific nozzles on the market for the containment of the drift phenomenon and nozzles with particular conformations, which also allow in many cases to optimise the distribution of the liquid and reduce drift. Anti-drift nozzles deserve special attention because of their significant impact on reducing product dispersion outside the target area. There are various types of these particular nozzles and they are now also offered in some standard configurations. Basically, their function is to generate a population of larger and dimensionally more uniform droplets than traditional nozzles of the same caliber (and therefore having the same flow rates at the same pressures of use). However, given the production of larger droplets, these nozzles must be carefully evaluated in case an accurate and continuous coverage of the target is required, such as in the case of treatments with covering or contact products. In these cases, in order to maintain the desired phytoiatric efficacy, it is advisable to increase the volumes of water distributed adequately. An even more marked result in terms of an increase in the average size of the sprayed droplets (and therefore a further decrease in the drift effect) can also be obtained through the use of "mirror" nozzles which, given the poor coverage they tend to guarantee, are especially suitable for treatments on bare ground. A further contribution to the reduction of the drift effect can be obtained by replacing the end nozzles placed at both ends with specific ‘boom end nozzles’ with asymmetrical spray patterns, as well as by adding specific anti-drift adjuvants to the phytoiatric mixture.

Ultrasonic sensors and active suspensions to optimize the distribution diagram. Thanks to the use of sensors that allow to measure the distance from the ground of the ends of the spray booms - including ultrasonic ones which, by emitting a very high frequency sound wave and then measuring the reflected wave (i.e. the echo), are able to evaluate the distance between the emission source and the target hit - it becomes possible (through a special control unit) to ‘pilot’ a pair of hydraulic pistons to keep the spray boom at the correct distance from the ground at all times. This technology is effective both with trunked soils and in the very frequent case of soils characterized by roughness capable of affecting the dynamic stability of the boom.

Optical Sensors and Artificial Intelligence. Through the use of special optical sensors mounted on drones, it is now possible to obtain NDVI (Normalized Difference Vegetation Index) maps, which can be used for the regulation of variable rate sprayers that are then able to differentiate the doses distributed in areas that differ from each other in terms of size and/or type of vegetation. The same vegetative vigour maps can also be obtained with vehicles that run along the rows on the ground, either by mounting these sensors on media that precede the treatment machine, or by mounting them on the sprayer itself, taking care to adequately precede them with respect to the device responsible for the ejection of the phytoiatric mixture. Switzerland's Avidor Hightech, for example, produces a device that regulates the flow of the sprayed liquid based on the information provided by the NDVI index derived from the maps. The modulation of the liquid flow rate can be done in different ways, by modifying the operating pressure of the nozzles, by modifying the forward speed, or by adopting modern solutions that involve the use of solenoid valves capable of working at high frequencies. Through this last system, called PWM (Pulse Width Modulation), it is possible to change the flow rate of the liquid dispensed without intervening on the operating pressure, i.e. keeping the size of the droplets constant while varying the volume of liquid dispensed. Independent control of each individual nozzle is also possible.

The "see&spray" technology. Treatments can be carried out only where necessary with the "see & spray" technique, relatedto the use of herbicides that are usually non-selective and are localized only in areas where weeds are actually present. Optical sensors such as the Green-seeker or the weed-seeker have been on the market for several years and represent solutions capable of identifying the presence of a plant on bare ground. When mounted on spray booms intended for inter-row weeding in weeded crops or for in-row weeding in vineyards and orchards, or for pre-emergence weeding on bare ground, these optical sensors allow the automatic opening of the nozzles only in the presence of weeds, avoiding intervening on areas where there is no target vegetation. Taking the next step, i.e. allowing the booms to identify the weed and distinguish the weed from the commercial crop, especially when operating in early post-emergence and the morphological characteristics of the plants at this stage are not yet easily distinguishable, however, requires a decidedly different level of image processing by an Artificial Intelligence, and it is a technique still under study whose commercial applications are still confined to very specific crops and weeds. Precisely for this reason, already in 2017 a giant like John Deere spent 205 million dollars to acquire Blue River Technology, a startup that has developed a system with cameras and Artificial Intelligence algorithms to recognize weeds and treat them with extremely precise and targetedherbicide jets.  From that year on, almost all the largest companies involved in the field of treatments, as well as many universities and government research institutions, have begun to try their hand at this field and are developing similar technologies.


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