• A crop sprayer should be calibrated in line with the manufacturer's recommendations.
• Always remember the objective of spraying is to achieve application of the best possible level of pesticides and fungicides.
As agrochemicals are probably the most expensive inputs for an arable farmer, it is very important to calibrate a crop sprayer in line with the recommendations of the manufacturer of the equipment. This will greatly help in achieving the best crop yield.
It is important to check the key components of a sprayer well in advance before starting to use the equipment. Careful attention needs to be paid to the pump, regulator, agitator, filters and nozzles.
If the pressure settings are correct and the pulsing pump does not deliver the required flow, it is likely that the pump has damaged valves or a weak diaphragm. Bearing in mind that the regulator controls the pressure for spraying in accordance with the agrochemical supplier’s recommendations, it must be in good condition. The main filters should be cleaned before the spraying season and this task should be carried out daily while the spraying operation is taking place.
Always remember the objective of spraying is to achieve application of the best possible level of pesticides and fungicides. Spreading too much chemical will burn the crop, and too little will allow the survival of pests, which may mutate to cause further problems in the future. For these reasons, the correct nozzles must be used together with the right chemical requirements. Usually, a flat fan is used for herbicides and a hollow cone for pesticides and fungicides.
After ensuring the sprayer is in good working condition, calibration must be carried out for each application. This does not have to be a daunting mathematical challenge. With Jacto sprayers the farmer can achieve the correct calibration using a measuring jug, establishing the tractor speed, marking out a 50m distance and monitoring the time on a watch.
The first step is to time the tractor and sprayer combination covering 50m. Next, the measuring jug should be held under one nozzle for the same time to give the litres per hectare, which will enable the adjustment of the tractor speed, or the sprayer’s pressure and water rate.
After establishing the desired water rate per hectare, the chemical mix for the tank can be calculated using the tank volume and litres per hectare to arrive at the necessary mix of chemicals. The time spent on this work will achieve the best use of agrochemicals and manage the cost of spraying. To avoid wastage by the boom overlapping markers, or GPS can be used to minimise overlap.
The choice of the optimum time of day should be established by seeking advice from the agrochemical supplier and anticipating expected rainfall. Advice and experience will guide the farmer to establish how long before anticipated rain spraying should be carried out, how fast the tractor can be driven without spoiling the application to the crop and avoiding the spray being drifted away.
Fergus Robley is the General Manager of FMD, the Massey Ferguson distributor