Oakes
Carrington
P.O. Box 531,
Influence of Tillage and Herbicides in Onion
2007 & 2008 Field Data
Sarah Gegner, Harlene
Hatterman-Valenti, Walt Albus, Collin Auwarter
North Dakota State
University and Oakes Research Extension Center
Figure 1. Hairy Nightshade weed
counts in strip-tillage
Figure 2. Hairy Nightshade weed
counts in conventional tillage
Figure 3. Common Lambsquarters
weed counts in strip-tillage
Figure 4. Common Lambsquarters weed counts in
conventional tillage
Table 1. Effect of tillage and
herbicide on onion grade/yield
Objectives
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 during the 2007 and
2008 field seasons at the North Dakota State University Research Extension
Center near Oakes, North Dakota, on an Embden loam soil. The experiment was set up as 2X4 factorial
in 2007 and a strip plot with herbicide as the whole plot and tillage as the
subplot in 2008. The whole plot
consisted of strip-tillage or conventional tillage; the subplots consisted of
herbicide treatments. The strips were
made fall 2006 and 2008 and again in the spring right before planting, using a
shank type unit; the conventional tillage treatment was Roto-tilled twice in
the fall and again before planting.
Onion cultivar Teton was planted April 20, 2007 and April 23, 2008 in
double rows at a rate of 250,000 and 285,000 seeds per acre, respectively. Plots were 6 feet wide and 17 feet long with
3 foot alleyways between each replicate.
Herbicides included DCPA (Dacthal), pendimethalin (Prowl H20),
oxyfluorfen (Goaltender), and bromoxynil (Buctril). DCPA and pendimethalin were applied as pre-emergence herbicides
on April 30, 2007 and May 1, 2008; 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, 2007 and 2008.
Pre-emerge applications were applied at 10 lbs/acre and 1.5 pt/acre for
DCPA and pendimethalin, respectively.
Micro-rate applications were applied at 2 oz/acre and 4 oz/acre for
oxyfluorfen and bromoxynil, respectively.
The entire experiment received a post-emergence application of clethodim
(Select) after the onions had reached the two-leaf growth stage and an
application of dimethenamid-P (Outlook) when onions were at the five-leaf
stage, to help minimize late-season weeds.
Best management practices were used for fertility, irrigation, disease,
and insect control throughout the entire experiment.
Herbicide effectiveness was evaluated through weed
counts using a square foot area in the center of each plot. Visual ratings were taken seven days after
the fourth micro-rate application to also evaluate weed control; a scale of
0-100 percent control was used 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 micro-rate application.
Plots were hand harvested on September 4, 2007 and
September 24, 2008. Onion bulbs were
graded into four classes according to USDA standards: small (1-2 ¼ inches),
medium (2 ¼-3 inches), large (3-4 inches) and colossal (4+ inches). Total marketable yield included grades
medium and large.
Results
Micro-rate herbicide applications made prior to the
two-leaf growth stage did not injure onions during establishment in either 2007
or 2008 field seasons(data not shown).
During the 2007 field season, tillage had an effect on the germination of
common lambsquarters and redroot pigweed.
There were significantly more weed seedlings in the conventionally
tilled treatments than the strip-tilled treatments. Hairy nightshade was significantly reduced with the weekly
applications of herbicide. Common
lambsquarters weed seedlings were significantly greater in the pendimethalin
treatment. Redroot pigweed and hairy
nightshade were best controlled with micro-rate applications of oxyfluorfen and
bromoxynil (data not shown).
During the 2008 field season, there was little to no
redroot pigweed pressure in all treatments.
Common lambsquarters and hairy nightshade weed pressure was
significantly reduced with the weekly applications of herbicides (Figures
1-4). DCPA had significantly greater
hairy nightshade weed pressure than the other three herbicides (Figures 1 and
2). Results of 2008 showed no significant
differences in tillage on weed seed germination (Figures 1-4).
In 2007 and 2008, 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. Results of
2007 indicated a significant increase in onions graded between 3- and 4-inch
diameters within the strip-tilled treatments (Table 1).
Conclusions
Yield data indicated that strip tillage has the
potential to yield significantly the same as conventional tillage. With the added savings of a strip-tilled
system, it may be more economical to utilize a strip-tillage system for onion
production.
Figure 1. Hairy Nightshade weed counts in strip-tillage
averaged across reps for 2008 field season.
Weed counts were taken at 4 weekly intervals starting
May 23, 2008.
Figure 2. Hairy Nightshade weed counts in conventional
tillage averaged across reps for the 2008
field season.
Weed counts were taken at 4 weekly intervals starting May 23, 2008.
Figure 3. Common Lambsquarters weed counts in strip-tillage
averaged across reps for the 2008
field season.
Weed counts were taken at 4 weekly intervals starting May 23, 2008.
Figure 4. Common
Lambsquarters weed counts in conventional tillage averaged across reps for
the 2008 field season. Weed counts were taken at 4 weekly intervals starting May 23,
2008.
Table 1. Effect of tillage and herbicide on onion
grade/yield.
|
|
|
Onion yield: kg/ha |
||||
|
Tillage |
Herbicide |
grade: small |
grade: med |
grade: large |
colossal |
total marketable |
|
Strip |
Prowl H20 |
4664 |
20918 |
26964 |
404 |
47881 |
|
Conv |
Prowl H20 |
8100 |
20451 |
23914 |
0 |
44365 |
|
Strip |
Dacthal |
6261 |
24963 |
24165 |
457 |
49128 |
|
Conv |
Dacthal |
7795 |
24317 |
25367 |
0 |
49684 |
|
Strip |
Goaltender |
8414 |
23412 |
15428 |
0 |
38840 |
|
Conv |
Goaltender |
10073 |
20532 |
7858 |
0 |
28390 |
|
Strip |
Buctril |
7723 |
21609 |
21483 |
888 |
43092 |
|
Conv |
Buctril |
10145 |
22174 |
21618 |
0 |
43791 |
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