Most farmers have already completed planting and are now preparing for the next major task – crop protection through responsible spraying with agrochemicals.

This is an essential operation for good yields, though it may be the most expensive input after fuel costs.

As with all other farming operations, preparation is key for efficient and cost effective coverage against weeds, grass, insects, pests, and diseases.

Critical to remember is that too much or too little chemicals have negative consequences. Excessive use of chemicals can burn crops, diminishing yields, while too little will allow pests to survive and possibly mutate to cause even more problems and limit yields.

Spraying tips

Sprayer check: What to look out for:

  • Carry out comprehensive checks and maintenance of sprayers well in advance of their use;
  • Pay attention to the water line from pumps, pipes, filters, regulators, agitator, filters, and nozzles;
  • Replace the oil level in the pump every season. Check if this was done at the end of last season and topped up to oil the level recommended by the manufacturer;
  • Replace worn-out and cracked hoses;
  • Check the status of the pump. If it does not deliver a stable pressure, or pulses when the pressure regulator settings are adjusted, it could have damaged valves, or a weak diaphragm;
  • Nozzles: Ensure that you have the appropriate and correct nozzle for the spraying. Often, the nozzles required are overlooked. It is important to take the advice given by the agrochemical suppliers such as recommendations for the water rate and droplet size. The regulator controls must also be in good working condition;
  • The minimum requirement should be a flat-fan nozzle to be used for herbicides and a hollow cone for pesticides. When using flat-fan nozzles, the fan pattern should be slightly offset by a few degrees to avoid larger droplets being formed where the fan patterns meet, which can burn the crops and cause unwanted yield limitation;
  • Clean filters at the end of every season and just before spraying begins. Clean after every day of spraying, or more often if the water is dirty. Daily filter cleaning during spraying helps to ensure maximum benefit for yield protection. It also helps to prevent down time and gives consistent pressure, during the small windows of opportunity for spraying.
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  • After ensuring that the sprayer is in good working condition, calibrate each application. This does not have to be a daunting task. With Jacto sprayers, a farmer can achieve the correct calibration using the supplied measuring jug, with the desired tractor speed timed over a 50-metre distance;
  • Use the timing to collect the discharge from one nozzle into the measuring jug to give the litres per hectare, or acre. If the water rate required needs adjusting, fine tune the pressure and, or the forward speed.

Chemical mix: After this, calculate the chemical mix using the tank volume with litres per hectare or acre to arrive at the necessary mix of chemicals. The time spent on this work will achieve the best use of agro chemicals and manage the cost of spraying.

To avoid wastage by the boom overlapping, markers or GPS can be used.

Temperature, wind and rain:

  • Establish the optimum time of day regarding temperature and wind speed from the agro-chemical supplier;
  • Consider expected rainfall. Advice and experience will guide you to establish how long before the expected rains should you spray to avoid unnecessary waste of chemicals and to achieve the positive results for crop yields.

Fergus Robley is the General Manager, FMD East Africa, the Massey Ferguson distributor


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