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Night Spraying Herbicides




Farming Smarter Project

Timeline: 2012 – 2014

Project Lead: Ken Coles

Collaborators: Lakeland Agricultural Research Association (LARA),
Bonnyville & SARDA Ag Research, Falher


Zero-tillage systems require timely pesticide applications to control weeds & diseases. A southern Alberta farmer tried spraying at night and had some success. Farming Smarter wanted to find if night spraying could provide a feasible alternative to poor daytime conditions and potentially improve efficacy due to greater absorption. Night spraying might provide farmers with the option to cover the same acres in a shorter time frame or to cover more acres with the same equipment.


  1. Determine if applying pesticides at night is a practical option for producers.
  2. Generate unbiased data on the efficacy and tolerance of night applications of pesticides.
  3. Uncover possible issues/complications associated with night spraying.


Research plots were established at three locations across Alberta: Lethbridge, Bonnyville and Falher.

In preseed burndown (PSBD) trials, plots were sprayed at label-recommended and three quarter-label rates with four herbicides: Prepass (Florasulam), Rounndup (Glyphosate), Aim (Carfentrazone) and Heat (Saflufenacil) according to the experimental design using hand held sprayers equipped with two meter booms and CO2 propellant at three different timings, day (12-2 pm), night (12-1 am) and early morning (4-5 am).

In-crop trials plots were sprayed at three quarter-label rate with the herbicides, Liberty (Glufosinate-ammonium), TM Muster + Select (Ethametsulfuron-methyl + Clethodim), Vantage™ Plus MAX II (glyphosate), Odyssey (Imazamox, Imazethapyr), Select (Clethodim), OcTTain (fluroxypyr, 2,4-D LV ester), Everest (Flucarbazone-sodium), Axial + Infinity (Pinoxaden + Prasulfotole, bromoxynil) and Barricade (Thifensulfuron, methyl, tribenuron methyl) depending on the target crop and experimental design, using similar equipment and spray timing as mentioned above in the PSBD trials.


The major conclusions drawn from our study are:
  1. The herbicides in PSBD and in-crop trials performed most effectively when applied in the day time (12-2 pm). Night time (12pm-1am) gave better results than the least effective Dawn time (4-5 am). We saw a substantial advantage of Day and Night time applications over the Dawn time application
  2. Although, Night time application performance was less often effective than Day time application, it performed better more often than Dawn time and, therefore, it could be useful as an alternate spray application timing when opportunities for Day time application are limited
  3. The results also suggest that moisture-stressed plants or a major rainfall event shortly after herbicide application could also reduce efficacies potentially rendering the herbicides totally ineffective, upsetting the performance patterns most often seen in our study


  • Pre-seed and in crop herbicides have most consistent results with day time applications
  • Broadleaf weed control is most sensitive to environmental condition
  • Glyphosate and Liberty are more sensitive to environmental conditions that wheat herbicides (OcTTain, Everest, Axial + Infinity, and Barricade)
  • Grassy herbicides may be improved with night time application
  • Early morning applications are least consistent
  • If in doubt, spray wheat in the morning, canola in the afternoon and peas in the evening
  • Plant response to environmental condiditons plays a major role
  • Consider type of herbicide – contact vs. systemic and mode of action
  • Consider weather conditions such as temperature, relative humidity, wind and delta T
  • Consider stress duration during before application from temperature, evaporative cooling, wind and delta T
  • Consider inversion risk, presence of dew, water volumes, nozzles
  • Consider weedy fields, hard to kill weeds, canopy structure…
  • Especially important for resistance management

Final Report

Project technicians actually got out at midnight to test the theory.

Read/download the final report

Night Spraying Herbicide Report






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