Tillage farmers who spray: the wind call, at your height

As a farmer-operator, you decide whether to go ahead with each spray pass. This call is made for fungicides, herbicides, plant growth regulators, and trace elements. Your decision depends on the wind at boom height, gusts, and Delta T conditions, all of which are critical factors for effective application and preventing drift.

This decision comes up often, typically 6 to 12 times per crop each season. During peak weeks, from March to July, you might be making this call daily, sometimes multiple times a day. A wrong call carries significant risks, including operator exposure and bystander exposure from drift, which can lead to crop damage on neighbouring land. There have been court findings where spraying in windy conditions was deemed negligent, highlighting the importance of this decision.

Your own document, which includes product labels and DAFM sustainable use rules, sets the specific limits for each application. The Wind Agent helps you assess if the conditions align with these limits, assisting your go or no-go decision for each hour you consider spraying. This support is vital for protecting your crops, the environment, and your reputation.

Your spraying operations are directly affected by wind at boom height, not the general wind at 10 metres, which is often cited in public forecasts. The Wind Agent provides wind information specifically at your working height, which is 2 metres for typical spraying applications. It shows both the mean wind speed and gusts at this specific height, giving you a precise understanding of the conditions where your spray is released.

Product labels, DAFM sustainable use rules, and your own professional judgement determine the wind limits for your work. These limits can vary by product, nozzle type, and the specific application you are undertaking. The instrument interpolates wind data to your exact working height, giving you a precise reading that is directly relevant to your sprayer boom.

This means you are looking at the wind where your sprayer boom is operating, not a general measurement from a higher mast or airport. This specific, height-matched data helps you compare actual conditions against the limits set by your product labels and other regulatory guidelines, ensuring you operate within acceptable parameters for drift management and efficacy.

The instrument provides the probability that the wind will be above your set limit, hour by hour. This is computed from a set of ensemble members, showing the fraction of these members that exceed your limit at 10, 80, 100, and 120 metres, which is then interpolated to your working height. This gives you a clear indication of the likelihood of encountering unsuitable wind conditions.

The Agreement Spine feature shows you where different weather models agree or disagree on the forecast. This gives you insight into the confidence behind the prediction; high agreement suggests a more reliable forecast. For instance, if 20 per cent of ensemble members show wind above your limit, you might proceed with caution, planning to monitor conditions closely and having a contingency plan.

If the odds are around 50 per cent, you might consider delaying the spray pass or adjusting your schedule to a different time of day when conditions are more favourable. If 80 per cent or more of the ensemble members indicate wind above your limit, it suggests a high likelihood of unsuitable conditions, prompting a no-go decision for that hour. These percentages are examples to help you interpret the information for your specific work and risk tolerance.

It's an example day. You wake up early, around 05:30, and check The Wind Agent for the day's forecast. The instrument shows a low probability of wind exceeding your 2-metre boom height limit for the first few hours, with mean wind around 3 mph and gusts to 6 mph, and Delta T is favourable for spraying.

By 06:00, you decide to prepare the sprayer, checking all nozzles and mixing the product. The forecast for 07:00 to 10:00 still shows low odds of exceeding your limit, with mean wind remaining under 5 mph and Delta T remaining within the ideal range. You start spraying at 07:30, taking advantage of the calm morning conditions.

At 09:30, you notice the odds of exceeding your limit are starting to climb for the afternoon, reaching 40 per cent by 14:00, with wind speeds predicted to increase. By 11:30, the forecast for 14:00 to 16:00 shows a 60 per cent chance of wind above your limit, with mean wind at 12 mph and gusts to 18 mph. You decide to finish the current field and stop spraying by 12:30, ensuring you complete the current pass before conditions deteriorate.

The afternoon forecast continues to show high odds of exceeding your limit, confirming your decision to stop. You then plan to resume spraying the next morning, when conditions are predicted to be more suitable, based on the instrument's forecast.

Your wind limit for spraying operations is not a universal figure; it comes directly from your own documents and operational guidelines. This includes the product labels for the chemicals you are applying, DAFM sustainable use rules, and your professional judgement based on experience and local conditions. These sources specify the maximum mean wind speed and gust conditions for effective application and to minimise drift.

For your work as a farmer-operator, the instrument is preset to a working height of 2 metres, which is typical for sprayer booms. The default limit for mean wind and gust at boom height is 11.8 mph. However, you can adjust this limit within the instrument to precisely match the specific requirements of the product you are using, the type of nozzle, or any other guidance you follow. This ensures the forecasts are always relevant to your exact operational constraints and regulatory obligations.

By inputting your specific limit, the instrument calculates the probability of exceeding that exact threshold. This personalised approach helps you align your spraying decisions with your regulatory and product-specific obligations, rather than relying on generic wind speed figures that may not apply to your specific situation.

The Wind Agent keeps a dated record of what was forecast and observed for wind conditions, the specific limit you used, and the call you made (go or no-go) for each day. This comprehensive record is important for several reasons in your work as a farmer-operator, providing a verifiable log of your decision-making process.

If a neighbour raises concerns about spray drift, or if an inspector from a regulatory body, such as the DAFM, inquires about your spraying practices, you have a clear, time-stamped record. This documentation shows the conditions you assessed and the decision you made at the time of spraying. It provides verifiable proof of your due diligence and adherence to best practices, which can be crucial in resolving disputes or demonstrating adherence to regulations.

This record helps you demonstrate that you adhered to your product label limits and DAFM rules, offering tangible evidence of your operational standards. It also serves as a valuable reference for your own operational review, allowing you to compare past forecasts with actual conditions and refine your decision-making over time. This record is a factual account of the conditions and your response, not an approval of your actions.

Irish conditions, particularly the Atlantic exposure, mean that wind is a constant and significant factor in tillage farming. The storm season, generally from October to March, brings stronger and more unpredictable winds, which can severely impact outdoor operations. However, even outside these months, localised wind patterns and sudden gusts can significantly affect spraying operations, demanding careful attention to conditions.

For tillage farmers, the peak spraying season runs from mid-March to the end of July. During this critical period, daily decisions regarding wind at boom height are paramount for effective application and to prevent drift. Autumn herbicide and slug pellet applications in October and November also require careful attention to wind conditions, as these can be just as sensitive to adverse weather and require precise application.

While Met Éireann provides national forecasts, the specific, height-matched wind data from The Wind Agent helps you apply these general forecasts to your precise operational needs at boom height. Irish agricultural guidance, often shaped by Teagasc advisers, consistently emphasises the importance of understanding local conditions and adhering to product label instructions for responsible farm management.