A Chemical Spray With a Shifting Wind and Stock in the Next Paddock
You are spraying a 12-hectare paddock of young lucerne with a knockdown herbicide using a boom spray on a still, mild morning. The label specifies a 3-day withholding period for grazing and warns against spray drift. Wind is forecast to pick up to 15 km/h from the north-west by early afternoon. The neighbouring paddock to the south-east holds 40 pregnant ewes and has a dam the sheep drink from. Your offsider has just filled the tank and wants to start immediately so the job is done before lunch. The farm owner is away and has left you in charge.
1. Decide whether to start spraying now. Set out the conditions you would check and the decision you would make.
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Check the label first - it is the controlling document. The label gives the withholding period (3 days for grazing) and drift warnings. Those are not optional. The next checks are wind speed and direction, temperature and humidity, and the sensitivity of the downwind crop or stock.
Apply the drift logic. Wind from the north-west would carry spray toward the south-east - straight at the ewes and their dam. At 15 km/h by afternoon, drift is a real risk even if it is calm now. Spraying now and hoping the wind holds is a gamble with someone else's stock and water.
Decision: do not start the full paddock now. Options in order of preference:
- Wait and reassess. Check the forecast for a window with light, steady wind blowing away from the ewes, and spray then. The lucerne will not be lost by waiting a day.
- Spray the upwind section only if the wind is genuinely light and forecast to stay that way, leaving a buffer strip near the boundary.
- Use a drift-reducing setup - lower boom height, coarser droplets, lower pressure - but only if the label allows it and the wind still suits.
Tell the offsider why. 'Done before lunch' is not the goal; a clean job with no off-target damage is. Note the decision and the conditions in the spray record.
2. The offsider says the ewes are 'miles away' and the dam is 'not our problem'. How do you handle the human side and the record-keeping?
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Human side: the offsider is not being reckless - they are focused on finishing the task, which is a normal pressure. Acknowledge that, then redirect to the shared risk. Explain that drift onto a dam or onto pregnant ewes can cause abortion, illness or residue problems, and that the cost falls on the farm, not just the neighbour. Give them a clear role in the safer plan (e.g. checking wind, setting the buffer, recording conditions) so they are part of the solution rather than overruled.
Record-keeping: complete the spray record as required - product, rate, date, time, paddock, weather at start and finish, wind direction and speed, applicator, and any buffer left. Note the withholding period (3 days) and mark the paddock so no one grazes it early. Record the decision to delay or modify and why; if a complaint arises later, that record is your evidence.
Judgement point: the exam is testing whether you can hold a safety and legal line under social pressure, and whether you can do it without damaging the working relationship. The right answer is firm on the decision, respectful to the person, and documented.