Electric shock emerges as an alternative in weed control.

Weeds represent a major challenge for farmers. A 2018 survey by GeoAgri found that approximately 20 million hectares of soybean-producing soil are infested with weeds. When not properly managed, weeds can be responsible for up to 80% of production losses, becoming an even greater control challenge as they adapt to the soil and develop resistance to herbicide applications. In the latter case, requiring more interventions increases the average cost of production, reducing crop profits. 

In this sense, in addition to soil management practices and chemical control through herbicides, an available solution for maintaining viable weed control is electric weeding, for ecological use. Electric weeding technology is based on the use and application of electrical discharges and/or electric shocks by specific equipment. The repetition rates of the electric shocks vary depending on the size and capacity of the generator, as well as the discharge surface area. 

The desiccating machine used for this purpose, mainly by organic soybean producers, is the Eletroherb, patented and launched by Sayyou Brasil, a company in the agricultural industrial equipment market based in São Bernardo do Campo (SP). 

How does it work?

Eletroherb is an agricultural implement used attached to the tractor's power take-off and whose main characteristic is having two distinct mechanisms for applying electric shocks. With different sizes and generator power, it can adapt to the different objectives of users. 

First, the mechanical energy generated by the tractor's engine is converted into electrical energy in the implement, creating high voltage and high frequency. This energy is then transmitted to the applicators, with the negative charge being transmitted to the rollers located at the front of the implement, which will be in direct contact with the ground, transferring electron flow. 

The positive charge is transmitted to the plates located closest to the tractor, which will be in direct contact with the weeds. This applicator directs the high voltage through the plants to their roots and consequently to the soil. In this cycle composed of a positive pole (plant) and a negative pole (soil), the electrical circuit is closed, making it safe and environmentally friendly. 

At the end of these applicators there is a series of electrodes, which are responsible for the electric shocks, which can vary from five thousand volts to up to 15 thousand volts, depending on the size of the desiccator machine. 

It is important to emphasize that for the most efficient operation of electric weeding, the ideal height of the weeds should be between 20 and 40 centimeters. However, the electrical discharges do not need to touch the target surface, since air can also be an electrical conductor. Furthermore, this method is not dependent on the time of day or day for application, and it has height control through a hydraulic system, allowing adjustment according to the target plant. 

Change caused by shock 

High-voltage shocks initially affect the leaves, but the consequences quickly spread throughout the plant, irreversibly altering its structure. The chlorophyll in the leaves is immediately affected, sap transport is interrupted, and the photosynthesis process is impaired. As a result of these disturbances, the root system is altered, compromising the absorption of water and essential nutrients available in the soil, killing the weed in a few days. 

Relationships between advantages and disadvantages

The major advantage of this equipment over conventional methods of weed control is the complete preservation of the environment: the Eletroherb electrocution method is an environmentally friendly solution as it eliminates the use of chemicals, among other things. On the other hand, there are disadvantages, that is, factors that can be improved to enhance performance.

Benefits

In the long term, it is more economically viable compared to other alternatives.

- Socially responsible, since it does not pose a risk to the health of workers and consumers.

- It does not suffer from drift, meaning there is no risk of it affecting other crops.

It can be used at any time of day, as it is not affected by factors such as dew.

- It leaves no residue in the soil and does not pollute water sources.

- It maintains organic cover on the soil.

- It is effective in combating herbicide-resistant weeds. 

Electric shocks do not kill earthworms and ants.

Disadvantages

- Reduced efficiency in removing perennial, old, and lignified weeds.

- It's not a very fast process (about 0,7 ha/h).

There is a risk of igniting already dry plants and straw located in the area to be controlled.

- High initial investment required for the purchase of equipment.

- It can destroy cultivated plants, since the method does not discriminate between the types of plants to be affected.

- It requires multiple applications to be effective.

- The need for relatively wide corridors for traffic.

Among the factors for improvement, the lack of selection between plant types stands out as a very significant deficit in this implement. Therefore, precision agriculture emerges as an important resource, and agricultural systems with sensors and cameras are able to differentiate crops from weeds, increasing the precision in performing the task. 

In any case, the use of electric weeding offers an important contribution to the mechanization and pest control sector, since it helps in the removal of weeds from crops, avoiding the use of herbicides. This technique, produced and marketed in Brazil, is undoubtedly an important ally in the development of agricultural production systems, such as organic and integrated production systems, due to its potential for use in various production chains and in different parts of the world.

*Per Gabriela Matos Cambrussi, Airton dos Santos Alonço e Gessieli Possebom, from Laserg/UFSM