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Agricultural chemicals and waste management

Calibration of chemical treatment equipment

A basic requirement for the efficiency of equipment to carry out chemical treatments is the uniformity of the application of the spray liquid, which is why the calibration of sprayers, or dressers, is one of the basic elements of Integrated Plant Protection.

An efficient sprayer must be properly adjusted: nozzles/atomizers selected, working pressure and speed of movement. Periodic calibration is carried out by an authorised diagnostician every 3 years, during the sprayer’s attestation, using specialised diagnostic equipment. Seasonal calibration is carried out by the farmer before each growing season, after the sprayer is stationary, after each change of nozzles, change of operating pressure or tractor. The aim is to achieve the required nozzle uniformity, droplet size and correct application rate per hectare. Calibration is also referred to as adjusting the sprayer and speed in such a way that the correct and planned application rate of the liquid and crop protection agent is achieved in the planned treatment.

In order to set the optimum spray rate and droplet rate, it is necessary, after consulting the conditions indicated on the product label:

  1. make a calculation taking into account: nozzle/atomizer spacing on the boom, actual operational speed of the sprayer in km/h (easiest way is to divide 360 m by the time taken to cover this distance, e.g. 360 m/ 60 s =6 km/h, or a shorter distance by conversion), determination of nominal spray output (q) from one nozzle (e.g. at 6 km/h using the formula q = Q * V * r/600, where Q – planned application rate per ha. at 6 km/h, using the formula q = Q * V * r/600, where Q is the planned application rate per ha, V is the measured speed of the sprayer, r is the nozzle spacing on the boom and 600 is a constant value),
  2. read the approximate liquid output value from the pressure table for the nozzle type in question,
  3. determine the actual flow rate from a single nozzle when the sprayer is switched on and all sections are switched on, by setting the nominal pressure for selected nozzles and measuring the flow rate of several nozzles, using measuring cups for 1 minute.

If the measured output is close to the calculated output, the pressure is left at the same level, otherwise it must be adjusted accordingly, and it is important that the deviation between individual nozzles does not exceed +- 5%. Knowing the output from one nozzle, we can calculate the volume of spray for spraying 1 ha and the amount of agent corresponding to the tank volume of the calibrated sprayer.

Field sprayers:

Calibration of seed and planting material dressers must be carried out exactly according to the procedure described in the dresser manufacturer’s instructions.