Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 76 Page 77 Page 78 Page 79 Page 80 Page 81 Page 82 Page 83 Page 84 Page 85 Page 86 Page 87 Page 88 Page 89 Page 90 Page 91 Page 92 Page 93 Page 94 Page 95 Page 96 Page 97 Page 98 Page 99 Page 100 Page 101 Page 102 Page 103 Page 104 Page 105 Page 106 Page 107 Page 108 Page 109 Page 110 Page 111 Page 112 Page 113 Page 114 Page 115 Page 11642 www.seed.ab.ca | Advancing Seed in Alberta applications at 5 a.m., 7 a.m., 9 a.m., 2 p.m., 8 p.m., 10 p.m. and midnight. “We wanted a visual demonstration for our field school, and was it ever. The results were strikingly different. It was almost like a bar chart in the field showing levels of efficacy. When herbicide was applied on hot days, you’d see that herbicide applied in the morning was good, but evening was bad, and then the efficacy would get better as the application got later in to the evening,” says Coles. Contrary to what one might expect, the field school results showed fairly good response for many of the 2 p.m. applications, even in cases where the application occurred when the tempera- ture was 27 C or more. “My thinking is that this is because the plants had only been under heat stress for an hour or two. And you see the same with cold stress at pre-seed burn-down. What is the point where the plant has been under cold stress longest? First thing in the morn- ing, which is when you see the poorest herbicide response.” The problem, of course, is farmers are constrained logistically by the narrow window in which they can usually apply herbicide. Assuming they can pick and choose when to spray often doesn’t work from an operational perspective. Therefore, because weeds respond differently to herbicides registered in different crops, Coles suggests scheduling one’s spraying with crop-specific guidelines in mind, particularly if you are struggling with herbi- cide resistance or high weed density. “I’d spray my canolas, both Liberty and glyphosate, in the middle of the day between 10 a.m. and 2 p.m.,” says Coles. “Wheat herbicides seemed to perform well under most condi- tions. For peas, certain kinds of products worked better in the evening, like herbicides for wild oat control. “I don’t think we have everything figured out. What we did learn more than anything was to pay attention to weather within the day and try to time accordingly, keeping in mind that plants’ ability to absorb herbicide is heavily influenced by stress,” says Coles. Madeleine Baerg Ken Coles, general manager of Farming Smarter, says the time of day herbicide is applied does impact its efficacy. “The time of day that herbicide is applied does impact its efficacy more than I ever expected.” —Ken Coles.