Oakes Irrigation Research Site
Carrington Research Extension CenterNorth Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Phone: (701) 742-2744, FAX: (701) 742-2700, E-mail: Walter.Albus@ndsu.edu

 

James Loken et al., North Dakota State University

 

Table 1.   Effect of adjuvant on herbicide efficacy and yield for weed control

See also  Effect of micro-rate application timing on herbicide efficacy and yield for weed control

 

Adjuvants improve micro-rate herbicide efficacy for weed control in onion, Oakes, ND.  Loken, James R., Harlene Hatterman-Valenti, Collin Auwarter, and Walt Albus.  An experiment was conducted at the Oakes Irrigation Research Site to compare early-season, broadleaf weed control of bromoxynil or oxyflourfen (water based formulation) applied as micro-rates plus adjuvants to the same herbicides applied as micro-rates without adjuvants for weed control in onion (Allium cepa L.).  The soil was an Embden sandy loam with 2.4% organic matter and 6.7 pH.  Onion variety ‘Teton’ pelleted seed was planted at 285,000 seeds/A using a Monosem four row double-line planter on April 23.  Plots were 6 ft wide by 17 ft long and arranged in a randomized complete block design with four replicates.  At time of weed cotyledon stage (May 16) herbicides were applied as micro-rates at 1/8 of their lowest labeled rates every 7 days, with four total applications.  Herbicide micro-rates were applied with a CO2 pressurized backpack sprayer.  A standard application of bromoxynil and oxyfluorfen was applied on June 24 (4-leaf stage) to control broadleaf weeds.  Another standard application of bromoxynil and oxyfluorfen was made on July 1 (5-6-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. Treatments were evaluated for overall control of redroot pigweed (Amaranthus retroflexus L.) and common lambsquarters (Chenopodium album L.) after all micro-rate treatments were completed using a visual evaluation on June 30.  On September 24, 5 ft of the middle two rows of each plot were 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. 

 

Herbicide application dates, timings, and environmental conditions for Oakes, 2008.

Application Date:                  5-16               5-26               6-3                 6-9                 6-24               7-1

Onion Stage:                        loop                flag-1 lf           1-2 lf               2 lf                 4 lf                  5-6 lf

Air Temp., (F):                      75                  50                  53                  61                  75                  75

Wind speed, (MPH):              5                    4                    6.5                 2.7                 5                    5

          

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

Spray Volume, GPA:             20                  20                  20                  20                  20                  20

 

Results:  Micro-rate herbicide applications plus adjuvants provided excellent control of common lambsquarters at the highest application rates regardless of herbicide and regardless of adjuvant. These applications provided superior control to the herbicide treatments without adjuvant. Redroot pigweed control was excellent across all herbicides and all application timings, due to the late emergence and poor weed growth during the early season.  Large grade yields were significantly greater with the high and medium application rates regardless of adjuvant, except where no adjuvant was included, where only the highest rate was significantly greater.

 

                                                     

Table 1. Effect of adjuvant on herbicide efficacy and yield for weed control in onion at Oakes, ND in 2008.

Treatment

 

Visual Evaluations

 

Yield

Herbicide

Adjuvant

Rate (herbicide + adjuvant)

 

colq1

rrpw2

 

 

Medium3

Large4

Total

 

 

-(product/A)-

 

-% control-

 

---------------------lbs/A--------------------

Oxyflourfen

MSO

2 oz + 0.5% v/v

 

95.0

100

 

15395.3

32771.4

51407.9

Oxyflourfen

MSO

1 oz + 0.5% v/v

 

85.0

100

 

22147.7

21427.5

46816.3

Oxyflourfen

MSO

0.5 oz + 0.5% v/v

 

62.5

100

 

20437.1

11343.9

38353.3

Oxyflourfen

POC

2 oz + 1 pt/A

 

95.0

100

 

13864.8

22867.9

39523.8

Oxyflourfen

POC

1 oz + 1 pt/A

 

87.5

100

 

18186.3

23588.2

44025.3

Oxyflourfen

POC

0.5 oz + 1 pt/A

 

53.8

100

 

14495.1

1530.5

24038.4

Oxyflourfen

None

2 oz

 

73.8

100

 

28539.9

9993.5

44025.3

Oxyflourfen

None

1 oz

 

48.8

100

 

9363.3

10173.5

25658.9

Oxyflourfen

None

0.5 oz

 

28.8

100

 

3511.2

0

8733.1

Bromoxynil

MSO

4 oz + 0.5% v/v

 

100

100

 

19896.9

29080.1

53118.5

Bromoxynil

MSO

2 oz + 0.5% v/v

 

93.5

100

 

19266.9

29530.3

52578.3

Bromoxynil

MSO

1 oz + 0.5% v/v

 

65.0

100

 

16565.8

15485.4

40334.0

Bromoxynil

POC

4 oz + 1 pt/A

 

100

100

 

22867.9

35202.2

62931.9

Bromoxynil

POC

2 oz + 1 pt/A

 

82.3

100

 

28810.0

30430.6

64462.4

Bromoxynil

POC

1 oz + 1 pt/A

 

62.5

87.5

 

17916.2

16205.7

39793.8

Bromoxynil

None

4 oz

 

87.5

100

 

22507.8

31511.0

58430.3

Bromoxynil

None

2 oz

 

40.0

100

 

6392.3

3331.2

14585.1

Bromoxynil

None

1 oz

 

27.5

100

 

2520.9

540.2

9543.3

Hand weeded check

--

--

 

100

100

 

20167.0

540.2

30160.5

Weedy check

--

--

 

0

0

 

0

0

1080.4

LSD

--

--

 

16.8

3.8

 

8884.9

15238.5

20658.6

1common lambsquarters, 2redroot pigweed, 3medium grade is 2.25-3 in, 4large grade is 3 in and >, 5oxyfluorfen water

 based formulation

 

 

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