Sprayers: sustainable technologies
Sprayers with product recovery are an innovative and ecological solution. Furthermore, more and more cases are being reported where this technology proves to be beneficial also from an economic point of view
Despite the growing concern of environmentalists and consumers about the effects of phytosanitary treatments in agriculture, it is well known that recourse to this practice is essential to obtain products with a high-quality level. The reduction and correct management of treatments remain a priority issue which calls for mechanization and new technologies for crop spraying. An analysis of the data concerning the functional tests, which have become compulsory for machines used for professional use to distribute plant protection products, clearly shows that the fleet of machines in circulation is rather old, with an average age of about 20 years. It is also undeniable that both spray booms and mistblowers, as well as machines defined as "special", such as those, for example, used for chemical stripping, have undergone a substantial technical evolution, which has significantly improved their environmental sustainability. For instance, with the implementation of Directive 2009/127/EC in 2011, manufacturers have introduced new equipment in the basic equipment. For example, all machines must now allow total interruption of spraying with a single control, they must enable easy filling and complete emptying of the main tank, precise and reliable definition of the volume to be sprayed, they must necessarily include a tank containing only water, dedicated to washing the sprayer, and they must also be designed to minimize the dispersion of the sprayed product by drift and percolation on the ground.
However, if the goal is to achieve maximum sustainability from the environmental point of view, all this is probably not enough. It is undeniable that, especially during the first treatments on tree crops, when the vegetation is still not at all or not very developed, the vast majority of the sprayed product is not spread on the target vegetation but is dispersed into the environment. Furthermore, both the recent introduction of regulations that contemplate the need to introduce buffer zones between treatment sites and sensitive sites (inhabited areas, bike paths, waterways, etc...) and the possibility of recovering the product otherwise dispersed to reuse it, generating significant economic savings, has prompted manufacturers to create eco-sustainable sprayers, i.e., equipped with a sort of "tunnel" inside which the treatment of the crop is carried out.
The possibility of carrying out the treatment in a confined environment or a sort of "mobile chamber" makes it possible to use the chamber's walls to intercept the product after it has passed through the target vegetation. This part of the distributed product would inevitably be lost with traditional sprayers. It is worth noting that this share is incredibly significant since with a conventional sprayer, in the initial stages of vegetation, it is common to disperse unnecessarily in the environment up to 80-90% of the sprayed product. While with machines equipped with recovery panels, almost all this product is recovered and reused. It is also true that the savings obtained with this new machinery decrease the more the barrier effect created by the vegetation increases in volume and density. The product savings in the last treatments are on average included in values ranging from 5 to 25%.
Based on these average values, and with reference to the already numerous studies published in the scientific literature, it is possible to estimate that, whereas the costs for the defense of an espalier vineyard vary on average between 300 and 1,000 €/ha, with the use of sprayers equipped with panels for the recovery of the product otherwise dispersed, the average saving is between 40 and 50% of the above figure.
On the other hand, the advantages are huge from the environmental point of view. This modern machinery can reduce up to 98% the phenomenon of drift, and this happens in practically all the conditions in which they can operate. Unfortunately, the complex architecture that characterizes them enables them to work only on espalier farming forms, making them bulkier, heavier, and more difficult to handle than traditional ones.
Despite these limitations, the demand for modern and truly eco-sustainable machines has led many Italian manufacturers to design a wide range of sprayers "with recovered panels", which are increasingly appreciated in Italy and abroad. What initially represented a small niche market has gradually expanded to become an increasingly important business for many Italian companies that find this particular market growing more and more. This is particularly true in those areas where, following the enactment of a series of very restrictive hygiene regulations requiring low environmental impact treatments on restricted portions of land (the so-called "buffer strips", sometimes very large), it has become almost impossible to carry out phytosanitary treatments on the perimeter strips of the plots using traditional machinery. However, precisely because of the use of innovative machinery equipped with product recovery panels, and therefore more "eco-sustainable" than traditional ones, it is now possible to carry out these treatments in full compliance with the requirements to protect vulnerable watercourses, sensitive areas, and bordering fields.
Let us now turn to agronomic considerations, given that in addition to certain savings in terms of the product to be used, it should also be considered that there are a number of critical issues that, if not adequately managed, can lead to unsatisfactory results.
The first issue is merely bureaucratic-legislative, and we hope it will be solved as soon as possible. As a matter of fact, it is well known that it is absolutely compulsory to respect the quantities indicated on the label of the plant protection product to be distributed for each hectare of cultivated area. It is also well known that, for example, the dosages indicated on the label always refer to a given quantity to be distributed per hectare (often with a minimum and a maximum dose). Instead, it would be logical to expect that for products acting by coverage, the reference would be made to the quantity of vegetation to be treated (referring, for example, to the leaf surface). In fact, it is perfectly clear to anyone familiar with the matter that a covering treatment carried out in April on a vine grown as a sapling requires, in order to obtain the same level of coverage, a much smaller quantity of product than the one required in July on a vine grown as a canopy. Moreover, in both cases, the amount of mixture phytoiatric required can vary 10 or more times, while the dosages reported on the label usually vary between the minimum and the maximum from 1 to 2. Yet this problem is further increased by mistblowers capable of intercepting and recovering the product otherwise dispersed, and only a desirable regulatory measure could solve the problem at the root.
Another critical aspect derives from filtering the mixture recovered from the panels, which is polluted by impurities such as dust and vegetation fragments that put a tremendous strain on the filtering system. Sometimes it is necessary to stop for cleaning, also to prevent the viscosity of the phytoiatric mixture in the tank from becoming too high.
However, from an operational point of view, the main difficulty is the considerable variability in the volume distributed. In fact, it is no longer linked, as on traditional machinery, only to the surface area worked, but is in fact related to the actual development of the vegetation. And even if it is possible to estimate it in broad terms, it is never possible to know it precisely before starting the operation, which unfortunately makes it impossible to determine the exact amount of mixture that will be distributed in the various plots. This means that it is almost impossible to get to the end of the treatment with the tank exactly empty. Instead, there will likely be a residual mixture that will have to be disposed of (or used in other fields). However, this problem is minimized by the most modern onboard computers that can measure the amount of product sprayed, recovered, and then report to the operator in real-time the amount of remaining autonomy.
Many national manufacturers are now committed to this particular market segment that includes machinery with additional high technological content. As a matter of fact, distribution management is almost always proportional to the speed of the machinery, thanks to the use of dedicated DPA control units and onboard computers. The control units also monitor the hydraulic adjustments where the opening and closing of the digging devices that support the screens for the recovery of the product are located. The latest innovations introduced are the use of specific apps installed on smartphones, tablets, or PCs to automatically complete the electronic campaign notebook.
