There are several factors to consider before and during herbicide spray application. Taking the appropriate steps to prepare for a successful application can save time, money and effort. While spray requirements may vary based on crop, location and herbicide formulation, there are steps that should be taken to ensure the best protection against weeds during the current crop season and to protect the effectiveness of the herbicide long term.
Mother Nature plays an important role in the success of herbicide application. In addition to the preventive and arbitrary actions necessary to increase herbicide effectiveness, working with natural conditions is extremely beneficial and mandatory since we do not control the weather or other natural factors.
Here are five considerations to get the most benefit when applying herbicides in the field:
1. Moisture Levels
Applying herbicides when a large amount of dew is present in the field, can negatively affect the efficacy of the herbicide. Dew can dilute the herbicide and lower the effective concentration. Furthermore, applications during heavy dew can lead to runoff, decreasing the effectiveness of the herbicide as well as distributing it in undesired areas.
Like many other parts of agriculture, the application of herbicides is dependent on temperature. Warm temperature and relative humidity are the best conditions to apply most herbicides. Extreme humidity can cause an increase in moisture on the plants, having the same effect on the herbicide as listed in number one.
Furthermore, temperature inversions can cause issues with off-target drift when applying herbicides. Temperature inversions occur when warm air rises and cooler air settles close to the earth where it is then immobile. Spraying during a temperature inversion can cause the herbicide to stay airborne until the inversion ends. By that time, the droplets may have made their way drastically off-target. This means that in addition to the herbicide not being effective in the intended field, it may have unintended, negative impacts to other areas.
3. Wind Speed
Wind speed can make or break the herbicide’s performance. It is important to check the wind speed before starting, but also be aware of and check any changes in wind speed during the application and make immediate adjustments as appropriate. Waiting for optimal wind speed may seem tedious, but it is very important for several reasons. Direction and force of the wind can be beneficial, but also devastating to herbicide application.
Ideal wind speed can vary, but according to the University of Minnesota Extension, wind speeds of 3 to 7 MPH winds are recommended. Above this speed, the wind can interfere with application and cause off-target drift. Conversely, spraying with 3 MPH wind or less could cause the herbicide application to be ineffective if a temperature inversion occurs. Spraying in wind speeds other than those listed on the herbicide label may not only be ineffective and potentially damaging to other areas, but it could also be illegal and have other undesirable consequences.
Selecting the correct nozzle is a very important factor to achieve the most effective herbicide application. The size of the droplets directly correlate with the nozzle and spray pressure, which also determines the amount of spray, the uniformity of the application and overall coverage. Nozzles can help with drift by controlling droplet size, but still allowing an applicator to get the adequate coverage with the herbicide.
A required nozzle size or spray droplet category should be listed on the label specific to the selected herbicide. In addition to using the correct nozzle, it is important to make sure the nozzle and sprayer are both clean, calibrated and in working order before heading to the field as blockage and worn-out equipment can cause uneven application. In addition, check your equipment during application and recalibrate as necessary. Also, be sure to properly clean your equipment as you change fields or products.
5. Boom Height
The height of the boom can also influence the effectiveness of your application and the amount of off-target drift during an application. A higher boom is more likely to have increased drift. Conversely, if the boom is too low, it can cause uneven patterns or skips in application. In general, the relationship between the boom height and the nozzle spacing should be a one-to-one ratio. For example, a 20-inch boom should have a 20-inch nozzle spacing.
When applying an herbicide, you should always follow the equipment manufacturer instructions and product labels to ensure best weed control. Educating yourself on herbicides and effective herbicide application will allow you to make more knowledgeable decisions when it comes to weed management. While these are not the only factors to consider when applying herbicides, ensuring that you’ve done everything in your power to increase herbicide effectiveness will pay off in the long run by helping you protect the crop and maximizing yield. Effective weed management will not increase a crop’s yield, but will help maximize the crop’s yield potential.