Recently, the question has been raised as to whether the effectiveness of various herbicides change as spraying times are altered throughout the day. The advent of night lights on tractors has allowed for more work to be done during the night when winds tend to be lowest. In contrast, many producers have been spraying during the day provided that wind conditions are acceptable. It is possible that the maximum effectiveness of the herbicides is impacted by these alterations in spraying time.
The function of herbicides relies on the metabolism of the crops and weeds, which changes throughout the day. In the early morning, plants may not be in full photosynthetic capacity which will reduce nutrient and compound transport within the plant. As well, dew present on the leaves could reduce absorption of herbicides by the plants. Consequently, movement of the herbicides into and within the plant may be reduced, which could decrease herbicide efficacy.
The night spraying trial will assess the effectiveness of different herbicides for the control of grassy and broadleaf weeds in wheat and canola when sprayed at three different times of day: night (midnight), early morning (4 am) and during the day (noon).
The night spraying trials are being grown in three locations across Alberta and this is the second year that LARA has participated. In 2012, the trial was considered preliminary and the trial will continue to be grown at the LARA farm in Fort Kent in 2014.
- To determine the optimal time of day to spray herbicides on wheat for control of broadleaf and grassy weeds.
- To determine the optimal time of day to spray herbicides on canola for control of broadleaf and grassy weeds.
- To determine if the optimal spray time changes in wheat with a later seeding date.
- To determine if the optimal spray time changes in canola with a later seeding date.
To mimic appropriate weed populations, the plots were first cross-seeded with mustard (broadleaf) on the front half of every replicate and oats (grass) on the back half of every replicate. The mustard was seeded to a depth of 0.5” at 50 plants/m2 and the oats were seeded at 150 plants/m2 to a depth of 1.5”. All seeding was done with the LARA five-row Fabro zero-till small plot drill.
Two sets of plots were established at the LARA Research Farm in Fort Kent in late May and early June at a depth of 1.5” and 180 plants/m2. Stettler wheat was treated with Raxil MD prior to seeding and blend fertilizer was side-banded at the time of seeding. A list of treatments can be found in Table 1.
Table 1. Night Spraying Wheat Treatment List.
Two sets of plots were established at the LARA Research Farm in Fort Kent in late May and early June at a depth of 0.5” and 50 plants/m2. The variety used was L130 treated with Helix Xtra. A blend fertilizer was side-banded at the time of seeding. A list of treatments can be found in Table 2.
Table 2. Night Spraying Canola Treatments.
The data from the past three years has been compiled and sent for analysis at Farming Smarter in Lethbridge and will be available in late winter 2015.