What are the main problems encountered in sprayers?

Matopiba is the region with the greatest agricultural growth in Brazil, with 73 million hectares distributed in the states of Maranhão (MA), Tocantins (TO), Piauí (PI) and Bahia (BA). The region is considered the last Brazilian agricultural frontier as it has large areas with potential for agricultural exploitation and which are currently extensive degraded pastures. By 2022, Brazil will have 70 million hectares of crops, of which ten million will be in this region, which will represent 16,4% of the planted area (Mapa, 2020).

However, the growing expansion of agricultural areas in Brazil has traditionally not been accompanied by the correct dimensioning of agricultural machinery, generating inadequate operating conditions and consequently losses in the production process. An example of this is the reduction in the application rate, the main objective of which is to spray a larger amount of area in a shorter period of time so that the entire area to be treated can be covered. This reduction makes the spray more concentrated and, therefore, more likely to generate residues and complications throughout the spraying system, such as clogging of spray tips or residues in filters and anti-drip valves.

According to information compiled by AgroEfetiva, based on its own database and also from the IPP project (Periodic Inspection of Sprayers), from FCA/Unesp, Botucatu (SP), it was possible to evaluate the application rate and the percentage of non-conformity of spray tips, filters and anti-steam valves that make up the sprayers used in Matopiba. In this context, nonconformity is understood as the lack of conformity, that is, the occurrence of problems that lead to the component being considered inadequate or having problems.

35 machines were inspected during the three-year period from 2016 to 2018 in the states of that region. Spray tips were considered unsuitable for use when they were clogged or worn. The line and suction filters were those with pesticide residue embedded in the mesh or that had cracks, and the anti-drip valves were those that were leaking. Based on this information, correlations were made between the application rate and the nonconformity of the mentioned components.

The average application rate applied in Matopiba was 74L/ha, with minimum and maximum values ​​of 37L/ha and 123L/ha, respectively. The highest average was found for Tocantins (94,5L/ha), followed by Bahia (76,3L/ha), Piauí (70,4L/ha) and Maranhão (63,7L/ha), as illustrated in Figure 1 It is important to highlight that the new leaflets for agricultural pesticides already contain information that takes into account good agricultural practices, such as application rate and droplet spectrum, to mainly avoid the risk of drift.

The percentage of adoption of an application rate followed a normal distribution, with the range between 60 and 70 liters per hectare being the most common, with a frequency of 28,57% of all properties visited (Figure 2). And nonconformities in spray tips, filters and anti-drip valves were present, respectively, in 69%, 40% and 37% of the total sprayers evaluated.

A strong and negative correlation was found between spray volume and non-compliance with spray tips (r=-0,75), filters (r=-0,73) and anti-drip valves (r=-0,71), as shown in Table 1 and Figure 3. This unprecedented result reinforces, above all, the negative effect of using more concentrated solutions (lower application rates) on the clogging or wear of spray tips. Furthermore, it illustrates the excessive retention of agricultural pesticides in the spray system filters (as this was the main problem observed). And the indirect effects of this practice may be related to the malfunction of anti-drip valves, as it causes residue to accumulate in internal components. However, other factors linked to the maintenance of the machines can cause damage to these spraying components.

The presence of residues in the machine's spraying components can cause serious damage to crops, especially when it comes to herbicides in highly complex agricultural environments, such as Matopiba. These problems will tend to be increasingly frequent in the coming years, in which the use of auxin mimics will be substantially increased due to new transgenic events that confer resistance to the active ingredients dicamba and 2,4-D in different crops, such as soybeans and cotton.

Therefore, efficient cleaning strategies for the spray system are essential for the complete removal of residues. AgroEfetiva has carried out several researches on this important aspect of application technology, in addition to research on drift, volatility, droplet spectrum and spray mixtures. For example, a machine should never be stored without properly cleaning the spray system. The book Understanding Application Technology: Phytosanitary Mixtures and Sprayer Decontamination (Publisher: Fepaf), provides a more in-depth discussion on this topic.

Therefore, the reduction in the application rate, and consequently the increase in the concentration of the spray mixture, makes the operation of applying agricultural pesticides more complex, with greater risks of damage and generation of residues in the spray components and may even be outside the scope of recommendations for leaflets and good agricultural practices. Therefore, it is essential to periodically inspect sprayers and clean them with efficient waste removal strategies, in order to guarantee operational and environmental safety and efficiency in applications. Using appropriate application rates will play an important role in this process.  

Vitor CR Araújo, FCA/Unesp; Fernando Kassis Carvalho, Rodolfo G. Chechetto, Alisson AB Mota, AgroEfetiva; Ulisses R. Antuniassi, FCA/Unesp