influence of seeding rate and herbicide programs on weed ...roundup ready alfalfa • approved for...

Influence of Seeding Rate and Herbicide Programs on Weed Control, Yield, and Quality of

Roundup Ready Alfalfa

Kevin W. BradleyRobert L. Kallenbach

Roundup Ready Alfalfa• Approved for sale and use in 2005

• New tool for weed management in alfalfa

• Technology Fee:– $125.00 per 50 lb bag– $ 2.50 per lb

• Technology fee has raised concerns regarding the ultimate utility of the technology

• Experiments conducted to:Evaluate the effect of seeding rate and herbicide programs (glyphosate vs. conventional) on weed control, yield, and quality of spring-seeded RR alfalfa

Materials and Methods

Alfalfa broadcast by hand at 4, 8, 12, and 16 lbs/A into a conventionally-tilled seedbed in late-March/early-April each year, then rolled and firmed with a field-scale cultipacker

Plots arranged in a RCB design with 4 replications

Herbicide applications made with CO2backpack sprayer delivering 15 gpa

Alfalfa density/m2 determined following the first and last annual harvests each year

Weed control and crop injury visually rated throughout the growing season

Materials and Methods:Herbicide Treatments and Timings

Preplant Incorporated Treatment– 4 ½ pts Eptam

POST Treatments (2-4 inch weeds)– 2 qts Butyrac + 1 ½ pts Poast Plus +

0.5% v/v crop oil concentrate– 5 fl ozs Raptor + 0.25% v/v non-ionic

surfactant + 2.5% v/v urea ammonium nitrate

– 22 fl ozs Roundup Weathermax + 2.5 lbs ammonium sulfate

Untreated Control

Materials and Methods:Forage Harvests & Quality Analysis

Forage yields determined by harvesting middle of each plot with HEGE forage harvester

Samples from each plot ground and % crude protein content determined by Near Infrared (NIR) Spectroscopy (Pacific Scientific 5000 scanning monochromator)

Influence of Herbicide Treatments and Seeding Rates on Large Crabgrass Control 4 Months After Planting (MAP)

Herbicide Treatments Seeding Rate

Columbia 2005

Mt. Vernon 2005

Mt. Vernon 2006

-- lbs/A --

Eptam 4.0 66 f 50 e 9 cd8.0 76 c-f 63 d 6 d

12.0 73 ef 75 c 10 cd16.0 86 a-e 86 b 24 c

Butyrac+Poast Plus 4.0 90 abc 83 bc 90 a8.0 96 a 83 bc 93 a

12.0 88 a-d 89 ab 98 a16.0 98 a 92 ab 98 a

Raptor 4.0 73 ef 53 de 19 cd8.0 78 c-f 58 de 58 b

12.0 70 f 84 bc 59 b16.0 80 b-f 90 ab 69 b

Roundup WthrMax 4.0 75 def 98 a 99 a8.0 94 ab 99 a 99 a

12.0 89 abc 98 a 100 a16.0 88 a-d 99 a 93 a

Trial Location

----- % Large Crabgrass Control 4MAPa-----

aMeans within a column followed by the same letter are not different (LSD=0.05) and can be used to make all herbicide by seeding rate comparisons.

Influence of Herbicide Treatments on Control of Other Grass Weeds 4 Months After Planting (MAP)

*There was not a significant effect of seeding rate, therefore all results were combined across herbicide treatments.*Other grass weeds included giant foxtail, yellow foxtail, goosegrass, and stinkgrass.

TreatmentsColumbia

2005Mt. Vernon

2006

Eptam 74 b 12 c

Butyrac+Poast Plus 95 a 83 a

Raptor 73 b 43 b

Roundup WthrMax 91 a 97 a

-- % Grass Weed Control 4 MAPa --

Trial Location


Influence of Herbicide Treatments on Broadleaf Weed Control 4 Months After Planting (MAP)

*There was not a significant effect of seeding rate, therefore all results were combined across herbicide treatments.*Broadleaf weeds included seedling curly dock, common lambsquarters, and redroot pigweed.

TreatmentsMt. Vernon

2005Mt. Vernon

2006

Eptam 95 b 100 a

Butyrac+Poast Plus 99 a 100 a

Raptor 97 ab 99 a

Roundup WthrMax 98 a 100 a

-- % Brdlf. Weed Control 4 MAPa --

Trial Location


Influence of Herbicide Treatments and Seeding Rates on Overall Weed Control 4 Months After Planting (MAP)

Herbicide Treatments

Seeding Rate

Columbia 2005

Mt. Vernon 2005

Mt. Vernon 2006a

-- kg/ha --

Eptam 4.0 65 e 72 e8.0 76 cd 76 e

12.0 75 cd 85 d16.0 80 bc 93 bc

Butyrac+Poast Plus 4.0 93 a 91 c8.0 95 a 91 c

12.0 93 a 94 abc16.0 98 a 96 abc

Raptor 4.0 70 de 72 e8.0 77 cd 77 e

12.0 75 cd 91 c16.0 74 cde 94 abc

Roundup WthrMax 4.0 79 cd 97 ab8.0 92 a 99 a

12.0 90 ab 99 a16.0 91 a 99 a

aIndicates locations where there was not a significant effect of seeding rate, therefore seeding rates were averaged across herbicide treatments.

Trial Location

----- Overall Weed Control 4 MAP (%)b -----

bMeans within a column followed by the same letter are not different (LSD=0.05) and can be used to make all herbicide by seeding rate comparisons.

47 c

93 a

97 a

67 b

Untreated, 4 lb/A seeding rate Untreated, 8 lb/A seeding rate

Untreated, 12 lb/A seeding rate Untreated, 16 lb/A seeding rate

Eptam, 4 lb/A seeding rate Eptam, 8 lb/A seeding rate

Eptam, 12 lb/A seeding rate Eptam, 16 lb/A seeding rate

Raptor, 4 lb/A seeding rate Raptor, 8 lb/A seeding rate

Raptor, 12 lb/A seeding rate Raptor, 16 lb/A seeding rate

Butyrac + Poast Plus, 4 lb/A seeding rate Butyrac + Poast Plus, 8 lb/A seeding rate

Butyrac + Poast Plus, 12 lb/A seeding rate Butyrac + Poast Plus, 16 lb/A seeding rate

Roundup WthrMax, 4 lb/A seeding rate Roundup WthrMax, 8 lb/A seeding rate

Roundup WthrMax, 12 lb/A seeding rate Roundup WthrMax, 16 lb/A seeding rate

Influence of Seeding Rate on Alfalfa Plant Density Following the First and Last Annual Harvests

Seeding Rate (lb/A)

First Harvest

Last Harvest

First Harvest

Last Harvest

First Harvest

Last Harvest

4.0 54 c 44 c 83 d 44 b 49 c 31 c

8.0 92 b 66 b 105 c 46 ab 69 b 37 b

12.0 109 a 87 a 140 b 48 a 82 b 41 ab

16.0 119 a 93 a 154 a 50 a 103 a 44 a

Alfalfa Density Following First and Last Annual Harvestsa

--------------------------------------- Plants / m2 ---------------------------------------

a Means followed by the same letter are not different, LSD=0.05.

Columbia 2005 Mt. Vernon 2006Mt. Vernon 2005

*There was not a significant effect of herbicide treatment, therefore all results were combined across seeding rates.

Influence of Seeding Rate on Alfalfa Stem Density Following the First and Last Annual Harvests

*There was not a significant effect of herbicide treatment, therefore all results were combined across seeding rates.

Seeding Rate (lb/A)

First Harvest

Last Harvest

First Harvest

Last Harvest

First Harvest

Last Harvest

4.0 123 c 238 c 178 c 262 c 175 c 294 b

8.0 203 b 332 b 219 b 307 b 246 b 362 a

12.0 234 a 425 a 268 a 324 ab 271 b 363 a

16.0 257 a 470 a 289 a 339 a 320 a 409 a

Alfalfa Density Following First and Last Annual Harvestsa

--------------------------------------- Stems / m2 ---------------------------------------



Influence of Herbicide Treatments on the Number of Alfalfa Stems Per Plant Following the First and Last Annual Harvests

*There was not a significant effect of seeding rate, therefore all results were combined across herbicide treatments.

TreatmentsFirst

HarvestLast

HarvestFirst

HarvestLast

HarvestFirst

HarvestLast

Harvest

Eptam 2.6 a 5.1 b 2.0 a 6.3 b 3.7 a 8.6 b

Butyrac+Poast Plus 1.9 d 6.0 a 2.0 a 7.1 a 3.1 b 10.1 a

Raptor 2.2 bc 4.2 c 2.0 a 6.3 b 3.6 a 9.3 ab

Roundup WthrMax 2.3 b 6.8 a 2.0 a 7.1 a 3.7 a 9.9 a

Untreated 2.0 cd 3.1 d 2.0 a 6.4 ab 3.1 b 8.9 b

Alfalfa Stems Per Plant Following First and Last Annual Harvestsa

------------------------------------- # Stems / Plant --------------------------------------



Influence of Herbicide Treatments on Individual and Total Yield of Roundup Ready Alfalfa (Columbia 2005)

*Bar sections with different lowercase letters indicate significant differences in yield within a given harvest, bars with different uppercase letters indicate significant differences in the total alfalfa yield for the year (LSD=0.05).

0

1000

2000

3000

4000

5000

6000

Eptam Butyrac +Poast Plus

Raptor RoundupWthrMax

Untreated

Treatments

Yiel

d (lb

/A)

Harvest 1 Harvest 2

a

ccd

b

a

c

a

b

aB

E

CD

A

Influence of Herbicide Treatments on Individual and Total Yield of Roundup Ready Alfalfa (Mt. Vernon 2005)


0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Eptam Butyrac + Poast Plus

Raptor RoundupWthrMax

Untreated

Treatments

Yie

ld (l

b/A

)

Harvest 1 Harvest 2 Harvest 3 Harvest 4

abd c b a

a

cb ab b

a

bab

a ab

a

abb

ab a

A

CB

A A

Influence of Herbicide Treatments on Individual and Total Yield of Roundup Ready Alfalfa (Mt. Vernon 2006)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Eptam Butyrac + Poast Plus

Raptor Roundup WthrMax

Untreated

Treatments

Yie

ld (l

b/A

)

Harvest 1 Harvest 2 Harvest 3 Harvest 4

c bc

b b

b

bb

ab ba

aab

a abab

abC C CB

A

b

b a

a


Influence of Herbicide Treatments and Seeding Rates on Crude Protein Content (Columbia 2005)

SeedingHerbicide Treatments Rate Harvest 1 Harvest 2

-- lbs/A --

Eptam 4.0 12.0 de 8.9 hij8.0 12.1 de 10.8 f-i

12.0 11.3 e 11.6 efg16.0 12.1 de 13.7 cde

Butyrac+Poast Plus 4.0 14.5 a 16.0 bc8.0 13.6 abc 17.9 ab

12.0 14.2 a 19.3 a16.0 13.9 ab 19.5 a

Raptor 4.0 12.6 cde 10.7 f-i8.0 12.7 cd 11.3 e-h

12.0 11.4 de 11.2 e-h16.0 11.5 de 13.7 cde

Roundup WthrMax 4.0 12.7 bcd 13.1 def8.0 12.1 de 17.6 ab

12.0 11.6 de 14.8 cd16.0 12.0 de 18.0 ab

Untreated 4.0 7.6 g 7.6 j8.0 7.6 g 8.6 ij

12.0 10.0 f 9.5 g-j16.0 9.2 f 10.1 g-j

Crude Protein Contenta

-------------------- % --------------------

aMeans within a column followed by the same letter are not different (LSD=0.05) and can be used to make all herbicide treatment by seeding rate comparisons.

Influence of Herbicide Treatments and Seeding Rates on Crude Protein Content (Mt. Vernon 2005)

SeedingHerbicide Treatments Rate Harvest 1 Harvest 2b Harvest 3b Harvest 4

-- lbs/A --

Eptam 4.0 21.1 e 19.9 de8.0 21.6 b-e 22.2 abc

12.0 21.8 a-e 22.1 abc16.0 21.7 a-e 21.7 abc

Butyrac+Poast Plus 4.0 22.5 a 21.5 bc8.0 22.1 a-d 21.8 abc

12.0 22.0 a-e 22.6 abc16.0 22.3 abc 22.2 abc

Raptor 4.0 21.7 a-e 21.2 cd8.0 21.5 cde 22.3 abc

12.0 22.3 abc 22.4 abc16.0 22.5 ab 22.6 abc

Roundup WthrMax 4.0 21.5 cde 22.3 abc8.0 21.7 a-e 23.1 a

12.0 22.4 abc 22.7 ab16.0 22.0 a-e 22.4 abc

Untreated 4.0 20.1 f 19.7 e8.0 21.5 cde 21.8 abc

12.0 21.2 de 21.3 bc16.0 21.4 cde 22.0 abc


------------------------------------ % ------------------------------------


23.6 a

22.9 bc

23.0 ab

22.7 bc

22.5 c 22.9 b

23.5 ab

23.3 ab

23.7 a

23.3 ab

bIndicates harvests where there was not a significant effect of seeding rate, therefore

Influence of Herbicide Treatments and Seeding Rates on Crude Protein Content (Mt. Vernon 2006)

SeedingHerbicide Treatments Rate Harvest 1b Harvest 2 Harvest 3 Harvest 4b

-- lbs/A --

Eptam 4.0 21.8 f 19.4 g8.0 22.8 c-f 20.4 fg

12.0 22.8 c-f 21.3 c-f16.0 23.8 abc 21.9 a-e

Butyrac+Poast Plus 4.0 22.4 ef 21.7 b-f8.0 23.7 abc 23.0 ab

12.0 23.9 ab 23.2 b16.0 24.0 a 23.1 ab

Raptor 4.0 23.1 a-e 21.1 def8.0 24.0 a 22.7 abc

12.0 23.7 abc 22.9 ab16.0 24.1 a 22.9 ab

Roundup WthrMax 4.0 23.5 a-d 22.6 a-d8.0 23.5 a-d 22.8 ab

12.0 24.0 a 23.2 a16.0 23.2 a-e 22.9 ab

Untreated 4.0 22.6 def 19.4 g8.0 23.6 a-d 20.7 efg

12.0 23.4 a-e 20.7 efg16.0 23.5 a-e 22.1 a-e

25.8 ab

25.9 a

24.7 c

25.2 bc

bIndicates harvests where there was not a significant effect of seeding rate, therefore seeding rates were averaged across herbicide treatments.


------------------------------------ % ------------------------------------


22.3 b

23.0 ab

23.6 a 26.0 a

22.9 ab

20.5 c

Conclusions:Weed Control

• Roundup WeatherMax or Butyrac + Poast Plus generally provided similar and highest control of large crabgrass and other grass weeds, regardless of alfalfa seeding rate.

• All herbicide treatments (conventional and glyphosate) provided greater than 95% control of the broadleaf weeds evaluated in these trials.

Conclusions:Forage Yield and Quality

• Butyrac + Poast Plus decreased initial and overall alfalfa yields at all locations

• Roundup WeatherMax resulted in similar or higher overall yields than conventional herbicide treatments at Mt. Vernon in 2005 and 2006, but not at Columbia in 2005 (dry year)

• Crude protein content was generally lower in untreated compared to herbicide-treated alfalfa at all locations, especially at the lower seeding rates

• Crude protein content was generally highest in response to Butyrac + Poast Plus or Roundup WeatherMax treatments

Excellent weed control, yield, and forage quality can be achieved with one application of glyphosate (Roundup) and seeding rates as low as 8 lbs/A in spring-seeded alfalfa. Longer-term studies will be required to determine the ultimate utility and economic feasibility of Roundup Ready vs. conventional alfalfa systems.

influence of seeding rate and herbicide programs on weed ...roundup ready alfalfa • approved for...

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