By Juan José Donoso, Director of Drops Consultores

Often, when an advisor instructs us to apply a specific volume of water in a given area with a particular phytosanitary product, our first step is to collaborate with the operator. We head to a row where we know the number of plants or meters, or the percentage of the hectare that corresponds to that row, and begin testing the speed and pressure needed to achieve the specified liters per hectare.

In many cases, we may hit the targeted liters per hectare, thus confirming that we are properly calibrated.

Alternatively, we can employ a mathematical method where, given the liters we are requested to apply, we select a tractor speed and are mindful of the working width or distance between rows, utilizing the following formula:

Q = (C x V x AT) / 600

Where:

• Q is the flow rate we need to deliver per minute to achieve the requested liters per hectare, expressed in liters per minute.
• V is the speed of the tractor in kilometers per hour.
• C is the desired coverage, expressed in liters per hectare.
• AT is the working width in meters, which for fruit trees corresponds to the distance between rows.

By dividing the result of this calculation by the number of nozzles, we obtain the flow rate that each nozzle must deliver to satisfy the application recommendation. This flow rate needs to be verified in the field to ensure proper calibration.

It is crucial to distinguish between being calibrated and being correctly regulated. Achieving the necessary liters per hectare does not always ensure optimal coverage, prompting us to analyze each component of the formula to enhance the quality and sustainability of our applications.

Application speed should be determined based on the type of terrain and the operator’s skill, as excessive speed can damage the sprayer, the tractor, and adversely affect operator comfort.

Moreover, the size of the fan impacts the product’s penetration into the foliage; if the speed is too high, the exposure time to air will be minimal, reducing application effectiveness. A higher air flow rate allows for greater speeds.

Selecting the most appropriate speed for the application is vital, considering that a tractor can achieve the same speed through different gears and revolutions.

Sprayer equipment pumps should not be exposed to more than 540 revolutions per minute (RPM) from the power take-off, though some manufacturers recommend an operational range between 400 and 540 RPM.

Operating near the maximum RPM ensures optimal pump and fan performance, but this also leads to higher fuel consumption and potentially excessive airflow for certain tree types. Conversely, working near the minimum could be inadequate for supplying the nozzles and maintaining proper agitation in the system.

The sprayer’s working width is determined by the planting layout, a detail that should have been addressed from the outset. With a larger working width, we must ensure that all plants are adequately reached.

The topic of application volume is extensive and warrants detailed analysis, which could be discussed at another time.