Oakes
Influence of Tillage and
Herbicides in Onion Field Data (Year 1)
Sarah Gegner, Harlene Hatterman-Valenti, Walt Albus, and Collin Auwarter
North Dakota State University and Oakes Irrigation Research Site
Table 1. Effect of tillage and herbicide
on weed emergence/control
The main objective for this research is to evaluate the potential for strip-tillage in onion production and to understand the influence of strip-tillage on factors such as weed seed germination, soil moisture content, soil temperature, and erosion control. In addition, the effect of strip-tillage on herbicide efficacy in onion prior to the two-leaf growth stage will be evaluated.
Materials and Methods
A field experiment was conducted at the North Dakota State University Research Station near Oakes, North Dakota, on an Embden loam soil. The experiment was arranged as a strip-block with four replicates. Main plot consisted of two tillage systems: strip-tilled and conventional-tilled with four herbicide treatments as sub-plots. The strips were made fall 2006 into wheat stubble using a shank type unit; the conventional treatment was Roto-tilled once in the fall. Onion variety ‘Teton’ seed (TE) was planted April 20 in double rows at a rate of 250,000 seeds per acre. Plots were 12 feet wide and 17 feet long with 4 feet between each replicate.
Herbicides included DCPA (Dacthal), pendimethalin (Prowl H2O), oxyfluorfen (Goaltender), and bromoxynil (Buctril). Application rates as well as tillage treatments are illustrated in Table 1. DCPA and pendimethalin were applied as a pre-emergence herbicide on April 30, whereas post-emergence applications with reduced rates of oxyfluorfen or bromoxynil (micro-rates) were made at four weekly intervals starting when annual broadleaf weeds reached the cotyledon to first-true-leaf stage; the first application was made on May 16. The entire experiment received a post-emergence application of clethodim (Select) on June 4, after the onions had reached the two-leaf growth stage and an application of dimethenamind (Outlook) when onions were at the five-leaf stage (July 3), to help minimize late-season weeds. Best management practices were used for fertility, irrigation, disease, and insect control.
Herbicide effectiveness was evaluated through weed counts in each plot using a 0.93 by 0.93 m square and visual ratings of control (0-100%) where 0 equals no control and 100 equals complete control. Annual broadleaf weeds of most concern were common lambsquarters, redroot pigweed, and hairy nightshade. Weed counts were taken seven days after each herbicide application. Plots were hand harvested on September 4 and allowed to field dry until September 10. Onion bulbs were graded according to USDA standards.
Herbicides did not injure onions during establishment (data not shown). Onion yield grade did vary between tillage system and herbicide but generally was only numerically higher with the strip-tillage and herbicide treatment for the various onion grades. Noticeable exceptions occurred with onions graded between 3.5 and 4 inch diameters where the conventional-tillage and herbicide treatment numerically yielded higher than its corresponding herbicide treatment in strip-tillage. The yield grade cwt/A for each tillage and herbicide treatment are illustrated in Table 1.
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Table 1. Effect of tillage and herbicide on weed emergence/control (5 wk after pre-emergence applications and 3 wk after first micro-rate application) and onion grade/yield at Oakes, ND.
|
Herbicide |
Rate |
Weed count (#/ft2) |
Onion yield
(cwt/A) |
||||
|
|
|
Colq* |
Rrpw* |
Hans* |
3 ½-4 in. |
3-3 ½ in. |
2 ¼-3 in. |
|
Strip-tillage |
|
|
|
|
|
|
|
|
DCPA |
10 lbs/A |
0.3 |
0.8 |
6.8 |
67 |
189 |
192 |
|
Pendimethalin |
1.5 pt/A |
1.0 |
2.3 |
6.5 |
70 |
157 |
201 |
|
Oxyfluorfen |
2 oz/A |
0.0 |
0.0 |
0.0 |
51 |
169 |
180 |
|
Bromoxynil |
4 oz/A |
0.0 |
0.0 |
0.0 |
20 |
141 |
164 |
|
Conventional |
|
|
|
|
|
|
|
|
DCPA |
10 lbs/A |
0.3 |
3.3 |
4.3 |
81 |
159 |
147 |
|
Pendimethalin |
1.5 pt/A |
1.5 |
5.5 |
9.5 |
60 |
155 |
177 |
|
Oxyfluorfen |
2 oz/A |
0.0 |
0.0 |
0.3 |
68 |
169 |
191 |
|
Bromoxynil |
4 oz/A |
0.0 |
0.0 |
0.0 |
34 |
84 |
132 |
|
LSD 0.05 |
|
1.3 |
2.4 |
5.5 |
40 |
69 |
37 |
*Abbreviations: Colq=common lambsquarters, Rrpw=red root
pigweed, Hans=hairy nightshade.
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