Poor weed control within the wheel tracks of the sprayer can be caused by a number of factors.
#1 Physical Stress: The physical damage caused to the weed by the wheel pressing down upon it may lead to poorer uptake and translocation of some products.
#2 Poor Deposition: When air is displaced from the sprayer moving forward its possible that the droplets can be displaced as well. This effect will become more visible as the speed of the sprayer increases, tires are wider and with more aggressive lug patterns.
#3 Increased dust levels: The high levels of dust that is produced by the wheels can interact with many products on the leafs surface. Products that are known to be influenced by dust include Glyphosate and Paraquat.
When assessing whether one of these factors has occurred its important to account for the secondary germination of weeds. As the compaction of the tires may have led to soil seed contact which resulted in germination. A simple method of avoiding this is to record the growth stage of the weed identified.
#Spray timing and drift potential
The operators that tend to have issues with dust avoid the issue by spraying on calm days and after a summer rainfall event. Another option would be to spray during times of low wind speed and just after an early morning dew. One thing to keep in mind though when spraying early in the morning is the high chance of a surface inversion.
#Adopt control traffic
By adopting a control traffic system it is possible to minimise the dust the amount of dust occurring as a result of the wheel tracks. The wheel tracks under controlled traffic system tend to be more compact in the top soil, which explains the lower dust levels.
The key is to minimising the amount of air that is displaced by the tires. Some farmers have been using mud flaps and mud guards that are capable of limiting the degree of air movement from the tires to the base of the boom. Wheel track nozzles are another great idea where an applicator will place much larger nozzles directly behind the wheels in order to ensure the same level of coverage. Other options that may be worth considering would be a higher clearance sprayer, wider wheel spacing’s and front mounted booms.
When looking to improve the level of spray coverage within the wheel tracks a grower will need to consider a number of factors. The best thing that growers can do is to utilize additional wheel track nozzles when using knockdown herbicides. If you would like some additional information feel free to check out my reference source for this article by following the link below.