Spraying precautions

Research points out flaws that affect pesticide applications and concludes that many of them could be avoided with simple actions adopted by operators. 

Controlling pests, diseases and weeds is very important to guarantee the quantity and quality of food, fiber and the production of raw materials for energy generation in agriculture. If this control is not done well, it is estimated that more than half of the expected final products may not be obtained. Therefore, it is necessary that correct methods of controlling the quality of pesticide applications are adopted on agricultural properties. To do so, producers and technicians need to understand exactly what most affects the quality of these operations.

Among these factors, we can highlight labor. Most of the time, greater attention is paid to operational conditions, to the detriment of the level of education and preparation of workers responsible for spraying. Therefore, a sophisticated machine will have little value if it is not operated by a professional qualified to follow the technical specifications. Therefore, operational and regulation and calibration procedures, which are the pillars of a good application, are often ignored or unknown. It is worth remembering that by law, rural workers applying pesticides must undergo adequate training to perform this task.

The maintenance, adjustment and calibration of agricultural machinery must receive special attention during spraying routines. Many researchers emphasize the importance of proper maintenance of agricultural machinery so that they perform their operational functions more efficiently, directly interfering with the company's profit. Currently, there are several initiatives throughout Brazil to encourage producers to carry out periodic inspection procedures on their sprayers. In some European countries this practice is mandatory and this contributes substantially to better control of spraying.

Fieldwork was carried out with the aim of investigating which factors have the greatest effect on the application of pesticides and, therefore, contributing to the adoption of more specific measures in the quality of pesticide applications. In this way, the analysis of parameters determining the quality of spraying was carried out, in order to contribute to other studies or propose more targeted actions, so that the most common problems can be corrected.

To this end, 60 sprayers were evaluated in the Alto Paranaíba region, Minhas Gerais, 30 hydraulic and 30 hydropneumatic, between the months of May and October 2012, highlighting the following parameters such as labor, calibration and equipment conditions. The analysis of each parameter was done through the evaluation of items that could represent them.

For labor, the following aspects were evaluated: safety in application, knowledge necessary for spraying, weather conditions for application, equipment for climate assessment and machine care. For the calibration procedure, the following were evaluated: engine rotation, sprayer speed, tips, adjustment and monitoring of weather conditions. To assess the condition of the equipment, leaks, hoses, pump filter, line filters, tip filters, refueling filter, protection of moving parts, syrup agitator, packaging washer, clean water reservoir, pressure gauge, valves were analyzed. anti-drip, spacing between tips, condition of the tips, bar alignment, manual accelerator, hour meter, tank level marker, line marker and noise levels.

We assigned a score to each item that ranged between zero and 15, where zero represented an absent or inadequate item and 5, 10 or 15 represented an present or adequate item. The data were analyzed using multivariate analysis methods, that is, using statistical models that could indicate which of the three parameters analyzed was the most decisive in the quality of the sprays. With this, numbers called “Wilk’s Lambda” were generated, where the lowest value represents the parameter that most influenced the final quality of the spraying (Table 01).

Observing table 01, it is possible to see that the parameters studied presented different values ​​of importance in the quality of the sprays, and that the calibration, as it presented the lowest Wilk’s Lambda value, was the most determining factor in this analysis. Labor, as it also presented a low value in this statistical analysis, can be considered another worrying factor in the quality of phytosanitary treatments.

For the characteristics explored within the equipment calibration parameter, a statistical analysis was also carried out, and the factors that presented lower Wilk’s Lambda values ​​were the most determining for the quality of pesticide application (Table 02). This means that these factors were the most problematic in most inspections, as they did not exist on the property or were in poor operating condition.

It is observed that climatic conditions are the least taken into account when applying chemical pesticides, followed by the actual application rate, which is the volume that the sprayer is actually applying, and also the nominal engine speed, which corresponds to the rotation of the power take-off. These factors, as they present lower Wilk's Lambda values, are those that most affected the quality of the spraying.

We found that most sprayers showed variations in the flow rates at the tips. Only 17% of the hydropneumatic sprayers analyzed had adequate nozzle flow, that is, their flow varied by less than 10% in relation to the original flow. Regarding hydraulic sprayers, 23% of them had the tip flow varying by less than 10%. This value is low, as most sprayers had problems at the tips, which lead to non-uniformity in volumetric distribution and error in the application rate.

The nozzles of the evaluated sprayers, in most cases, operated at a pressure consistent with the technical specifications. Only 13% of hydraulic sprayers were operating at pressure above the recommended level. They had fan-type tips, which generally operate with working pressures between 2 and 4 bar, and withstand smaller variations in working pressure. In hydropneumatic sprayers, all nozzles had a conical jet, which can generally operate at higher pressures, which is probably the reason why there was less occurrence of sprayers with pressures above those recommended.  

Another problem encountered is that half of the sprayers evaluated did not apply the recommended spray volume. Hydraulic sprayers, on average, applied 4% less than the recommended volume, while hydropneumatic sprayers applied 7,6% less.

We also found that monitoring of climate conditions is carried out on few properties. Other research found that in 15% of the properties evaluated, there was no monitoring of weather conditions, due to the lack of specific equipment for this purpose. If compared to the data found in this work, it is observed that little attention is paid to monitoring weather conditions in the Alto Paranaíba (MG) region during spraying, especially in hydraulic sprayers.

The discriminant analysis and the scenario found leads us to conclude that the largest number of problems found are related to the labor involved in the application. Many problems observed could have been easily resolved if there had been better selection, training and qualification of operators. It is therefore suggested that training and updates be carried out more frequently so that operators are motivated and aware of the appropriate adjustment and calibration procedures, as well as the care of the sprayer before, during and after spraying.

Guilherme Andrade Gontijo, Diego Sichocki, Renato Adriane Alves Ruas, UFV/CRP

Article published in issue 149 of Cultivar Máquinas.