Properly timed and executed herbicide applications can significantly enhance weed control, but it requires careful consideration of various factors, including environmental conditions, product selection, and application techniques.
Let’s look at some best practices for in-crop spraying to help you achieve optimal results.
Best practices for in-crop spraying:
1. Timing of herbicide application
The timing of herbicide application is crucial for maximizing effectiveness. Spraying at the right time of day can enhance the absorption and action of herbicides. Generally, the best time to spray is during the day when plants are actively growing, typically this is between 9:00 a.m. and 5:00 p.m.
Morning vs. Evening Spraying:
Morning Spraying: Early morning spraying takes advantage of cooler temperatures and higher humidity, which can reduce the risk of herbicide volatilization and drift. Spraying in the morning before the temperatures rise can reduce the risk of rapid evaporation, meaning more time for the herbicide uptake.
Evening Spraying: Late afternoon or early evening spraying can also be effective as temperatures cool down and wind speeds typically decrease. This timing can reduce the risk of herbicide evaporation and drift.
2. Evaluating Environmental Conditions
Environmental conditions play a significant role in herbicide effectiveness and safety. Here are key factors to consider:
Drought Conditions
Drought stress can affect both crops and weeds, altering their response to herbicides. Plants under drought stress often have thicker cuticles and reduced growth, which can limit herbicide uptake. To maximize effectiveness:
- Use the Full Label Rate of Systemic Herbicide Concentration: In some cases, increasing the concentration within the label guidelines of the herbicide may help penetrate the thicker cuticles of drought-stressed weeds. Also applying systemic herbicides in the morning can limit crop injury.
- Apply contact herbicides at night: This will result in less injury to the crop, and contact herbicides can be more active in drought times.
Wind Speeds
Wind speed is a critical factor in preventing herbicide drift, which can cause off-target damage and reduce effectiveness. Ideal wind speeds for spraying are between 3 to 10 km/h. Here’s how to manage spraying in windy conditions:
- Use Coarse-Spraying Nozzles: These nozzles produce larger droplets that are less likely to be carried away by the wind.
- Spray Early or Late: Wind speeds tend to be lower in the early morning or late evening, making these times preferable for spraying.
- Avoid High Winds: Do not spray when wind speeds exceed 10 km/h to prevent drift and ensure the herbicide reaches the target area.
Humidity Levels
Humidity can significantly affect herbicide performance. High humidity levels (above 50%) are generally favourable as they slow the evaporation of spray droplets, allowing more time for herbicide absorption. In regions across Canada, monitoring humidity levels can help optimize spraying conditions.
3. Managing Temperature Inversions
Temperature inversions occur when a layer of cool air is trapped near the ground by a layer of warmer air above it. This condition can cause herbicide droplets to remain suspended in the air, leading to off-target drift. To avoid spraying during inversions:
- Check Conditions: Inversions typically occur in the late evening or early morning when the air is still. Avoid spraying during these times unless you can confirm the absence of an inversion.
- Visual Indicators: Fog, dew, or smoke remaining near the ground can indicate an inversion. If these are present, delay spraying until conditions improve.
4. Selecting the Right Herbicide
Choosing the appropriate herbicide is essential for effective weed control. Glyphosate, such as Credit Xtreme are widely used for their broad-spectrum activity and effectiveness. When selecting a herbicide:
- Understand Weed Species: Identify the weed species present in your fields and choose an effective herbicide for those species
- Consider Herbicide Resistance: Use herbicides with multiple effective modes of action and rotate herbicides with different modes of action to slow the development of herbicide-resistant weed populations.
5. Optimizing Application Techniques
Effective spraying techniques ensure uniform coverage and penetration. Here are some tips:
- Calibrate Equipment: Regularly calibrate your sprayer to ensure accurate application rates.
- Adjust Nozzles: Select nozzles that produce the appropriate droplet size for your conditions. Fine droplets improve coverage but are more prone to drift, while coarse droplets reduce drift but may provide less coverage.
- Maintain Speed: Keep a consistent speed while spraying to ensure even application across the field.
Maximizing the effectiveness of crop spraying involves a strategic approach that considers timing, environmental conditions, herbicide selection, and application techniques. Whether you’re tank-mixing and spraying pre-emergent or pre-seed burndown herbicides with glyphosate or cleaning up fields with an in-crop herbicide, adhering to best practices can enhance herbicide performance while minimizing risks.
Incorporating these practices into your crop management plan ensures effective weed control and effective use of herbicides.
