Oakes
Weed control using herbicides applied as micro-rates in onion
Loken,
James R., Harlene Hatterman-Valenti, Collin Auwarter and Walt Albus.
An experiment was conducted to compare early-season weed control of bromoxynil, oxyflourfen (water based formulation), metribuzin, and aciflourfen applied at micro-rates to a standard preemergence treatment of DCPA in onion (Allium cepa L.). The soil was a Maddock sandy loam with 2.2% organic matter and 7.4 pH. Onion variety ‘Teton’ pelleted seed was planted at 220,000 seeds/acre using a Monosem four row double-line planter on May 4. Plots were 6 ft wide by 17 ft long and arranged in a randomized complete block design with four replicates. The standard preemergence treatment of DCPA was applied one week after planting (May 11). At time of weed cotyledon stage (May 15) herbicides were applied as micro-rates at 1/16, 1/8, and 1/4 of their lowest labeled rates every 7 days, with 2 or 3 total applications. Herbicide micro-rates were applied with a CO2 pressurized backpack sprayer. A standard application of bromoxynil, oxyfluorfen and dimethenamid-P was applied on June 20 (3-leaf stage) to control broadleaf weeds. Another standard application of bromoxynil and oxyfluorfen was made on July 10 (5 to 6-leaf stage) as a final late-season broadleaf weed control measure. Standard applications were applied using a tractor-mounted sprayer. Best management practices were used for fertility, disease, insect and grass weed control. Fifty lbs/acre of 28% nitrogen was applied on April 18. Liquid nitrogen (30 lb/acre at 28%) was applied via streambar on June 7, June 21 and July 11. Treatments were evaluated for overall control of redroot pigweed (Amaranthus retroflexus L.) and common lambsquarters (Chenopodium album L.) seven days after each micro-rate treatment using weed counts and approximately two weeks after the first standard application using a visual evaluation. On October 4, ten feet from the middle two rows of each plot was harvested for grade and yield analysis. After harvest, onions were allowed to cure and then were graded. Split and diseased bulbs were graded as culls regardless of diameter. Samples were taken to check for the percentage of double-centered bulbs.
Herbicide application dates, timings and environmental conditions for Oakes, 2006.
Onion Stage: PRE PRE E 1-1½ lf 3 lf 5-6 lf
Air Temp., (F): 57 60 70 70 73 73
Wind Velocity, (MPH): 7 10 6 8 1 0
Soil Temp., (F): 50 55 60 79 82 81
Operating Pressure: 40 psi 40 psi 40 psi 40 psi 40 psi 40 psi
Nozzle Type: Flat Fan Flat Fan Flat Fan Flat Fan Flat Fan Flat Fan
Nozzle Size: 8002 8002 8002 8002 8002 8002
Results: Micro-rate herbicide applications did not appear to injure onion during establishment. Plant counts reinforced visual weed control ratings. Visual ratings indicated that excellent common lambsquarters and redroot pigweed control occurred early on with 3 applications of bromoxynil at 0.063 lb ai/acre and 3 applications of oxyfluorfen at 0.013 lb ai/acre. The greatest total and large diameter onion yields were also associated with the oxyfluorfen treatment. Early-season common lambsquarters control was necessary to achieve high yields with the micro-rate treatments.
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Table 25. Effect of herbicide, rate, and number of applications on weed control, onion yield and grade at the Oakes Irrigation Research Site in 2006.
|
|
Micro-rate |
# of App. |
Population colq |
4Population rrpw |
5% Weed Control colq |
% Weed Control rrpw |
3Yield
(cwt/A) |
||||
|
Herbicide |
(lb ai/A) |
|
11WAT1 |
2WAT3 |
1WAT1 |
2WAT3 |
29WAP |
9WAP |
2.25-3 in |
3 in or > |
Total |
|
Bromoxynil |
0.016 |
2 |
44 |
31 |
3 |
3 |
15 |
21 |
5 |
0 |
5 |
|
Bromoxynil |
0.031 |
2 |
28 |
30 |
1 |
5 |
24 |
43 |
32 |
0 |
32 |
|
Bromoxynil |
0.063 |
2 |
22 |
4 |
2 |
4 |
69 |
61 |
167 |
110 |
278 |
|
Bromoxynil |
0.016 |
3 |
37 |
36 |
4 |
3 |
9 |
35 |
26 |
2 |
28 |
|
Bromoxynil |
0.031 |
3 |
58 |
10 |
2 |
1 |
81 |
83 |
132 |
114 |
246 |
|
Bromoxynil |
0.063 |
3 |
10 |
1 |
4 |
3 |
99 |
95 |
161 |
114 |
275 |
|
Oxyfluorfen |
0.003 |
2 |
11 |
22 |
1 |
2 |
13 |
26 |
44 |
4 |
48 |
|
Oxyfluorfen |
0.006 |
2 |
4 |
26 |
1 |
1 |
28 |
63 |
114 |
34 |
148 |
|
Oxyfluorfen |
0.013 |
2 |
4 |
10 |
0 |
1 |
73 |
71 |
154 |
190 |
343 |
|
Oxyfluorfen |
0.003 |
3 |
7 |
18 |
1 |
2 |
14 |
30 |
66 |
49 |
115 |
|
Oxyfluorfen |
0.006 |
3 |
3 |
7 |
0 |
2 |
85 |
79 |
195 |
219 |
414 |
|
Oxyfluorfen |
0.013 |
3 |
1 |
3 |
0 |
0 |
99 |
100 |
108 |
350 |
458 |
|
Metribuzin |
0.005 |
2 |
25 |
24 |
1 |
1 |
3 |
21 |
0 |
0 |
0 |
|
Metribuzin |
0.009 |
2 |
33 |
24 |
5 |
6 |
6 |
31 |
0 |
0 |
0 |
|
Metribuzin |
0.019 |
2 |
23 |
11 |
1 |
1 |
0 |
21 |
6 |
0 |
6 |
|
Metribuzin |
0.005 |
3 |
18 |
31 |
9 |
16 |
6 |
25 |
0 |
0 |
0 |
|
Metribuzin |
0.009 |
3 |
22 |
27 |
1 |
1 |
3 |
19 |
2 |
0 |
2 |
|
Metribuzin |
0.019 |
3 |
10 |
6 |
1 |
2 |
28 |
44 |
54 |
0 |
54 |
|
Acifluorfen |
0.016 |
2 |
17 |
21 |
0 |
2 |
0 |
3 |
0 |
0 |
0 |
|
Acifluorfen |
0.031 |
2 |
18 |
27 |
4 |
2 |
6 |
3 |
28 |
2 |
30 |
|
Acifluorfen |
0.063 |
2 |
16 |
19 |
2 |
1 |
20 |
8 |
85 |
46 |
132 |
|
Acifluorfen |
0.016 |
3 |
34 |
35 |
3 |
7 |
3 |
3 |
0 |
0 |
0 |
|
Acifluorfen |
0.031 |
3 |
16 |
14 |
3 |
2 |
10 |
3 |
30 |
2 |
32 |
|
Acifluorfen |
0.063 |
3 |
19 |
24 |
2 |
1 |
28 |
31 |
97 |
27 |
124 |
|
DCPA - PRE |
8 |
— |
25 |
25 |
2 |
3 |
85 |
87 |
199 |
248 |
447 |
|
Hand-Weeded Check |
— |
0 |
0 |
0 |
0 |
0 |
100 |
100 |
173 |
286 |
|
|
LSD (0.05) |
|
|
28 |
18 |
4 |
5 |
22 |
36 |
60 |
110 |
141 |
1 1WAT1 denotes one week after first treatment,
2 9WAP denotes nine weeks after planting,
3Cull yield not shown,
4
Average populations taken from a 1 ft2 area,
5 colq
and rrpw denote common lambsquarters and redroot pigweed respectively.
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