YielixSpray Drift Risk Calculator — Wind, Nozzle & Buffer Zone Assessment
Assess spray drift risk before every application using wind speed, nozzle droplet size, buffer distance, delta-T, and boom height. The calculator scores each factor and produces an overall drift risk rating so you can decide whether conditions are safe to spray. Reduce off-target movement, protect sensitive areas, and stay compliant with label buffer requirements.
Inputs Explained
- Wind Speed
- Current or forecast wind speed in km/h or mph. Wind is the primary driver of spray drift and carries the highest weight (30%) in the overall score. Ideal range is 5-15 km/h.
- Nozzle Type / Droplet Size
- Select your nozzle classification from Fine to Very Coarse per the ASABE S572.3 standard. Coarser droplets are heavier and less prone to drift.
- Buffer Distance
- The distance between your spray area and the nearest sensitive area (waterway, residence, organic field). Compared against recommended minimums for your nozzle type.
- Delta-T (Wet Bulb Depression)
- The difference between dry bulb and wet bulb temperature in degrees Celsius. Values below 2 indicate inversion risk; above 8 means rapid droplet evaporation. Ideal range is 2-8.
- Boom Height
- Height of the spray boom above the target canopy in centimeters. Lower boom heights reduce the time droplets are airborne. Keep at 50 cm or below for best results.
How This Calculator Works
Worked Example
Planning to spray a herbicide with a medium nozzle, wind at 12 km/h, delta-T of 5°C, 20 m buffer, boom at 60 cm
- 1. Wind speed score
12 km/h is moderate — acceptable but not ideal. Partial score on the wind factor.
- 2. Nozzle score
Medium nozzle provides reasonable coverage but is more drift-prone than coarse. Moderate score.
- 3. Buffer distance score
20 m exceeds the 15 m minimum for medium nozzles. Good score on buffer factor.
- 4. Delta-T score
5°C is within the ideal 2-8°C range. Full score — no inversion or evaporation risk.
- 5. Boom height score
60 cm is slightly above the ideal 50 cm. Minor deduction.
Overall drift risk: Moderate. Conditions are acceptable but consider switching to a coarse nozzle or waiting for lower wind.
How to Interpret Your Results
| Condition | What It Means |
|---|---|
| Low Risk (Green) | Conditions are favorable for spraying. All factors are within safe ranges. Proceed with application following label directions. |
| Moderate Risk (Amber) | One or more factors are marginal. Consider adjusting nozzle size, boom height, or waiting for better conditions. Extra caution near sensitive areas. |
| High Risk (Red) | Conditions pose significant drift risk. Do not spray. Wait for wind to drop, temperature inversion to clear, or switch to a much coarser nozzle with larger buffer. |
Common Mistakes to Avoid
Spraying in calm conditions thinking no wind means no drift
Calm conditions (under 5 km/h) often indicate temperature inversions where spray hangs in the air and drifts unpredictably for long distances. A light breeze (5-10 km/h) is actually safer.
Using fine nozzles near sensitive areas for better coverage
Fine droplets provide coverage but drift much farther. Near sensitive areas, always use the coarsest nozzle that provides adequate efficacy.
Ignoring delta-T when planning spray timing
Delta-T below 2°C (common early morning and late evening) signals inversions. Delta-T above 8°C means droplets evaporate rapidly. Check weather data before spraying.
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