roundup ready vs. liberty link soybeans crops - daniel stephenson...harvest date august 9 th. ......

Roundup Ready vs. Liberty Link

Soybeans

Daniel Stephenson, Ph.D.Daniel Stephenson, Ph.D.

Weed Scientist

LSU AgCenter

Got to understand the herbicide

first!

• Not just Roundup Ready vs. Liberty Link

• Not just Ignite vs. Roundup PowerMax or • Not just Ignite vs. Roundup PowerMax or

Touchdown Total or generic glyphosate

• GLYPHOSATE vs. GLUFOSINATE

Glyphosate vs. Glufosinate

• Both are non-selective herbicides

• Broad-spectrum annual and perennial broadleaf

and grass weed control

• Chemical structures

HO C CH CH2 CH2 P O ║ ║

O O

CH3

−NH4

+

NH2

HO C CH2 NH CH2 P O NH3 CH ║ ║

O O

OH CH3

CH3

− +Glyphosate isopropylamine salt

Glufosinate ammonium salt

Glyphosate

• Mode of action:

• Inhibits enolpyruvyl shikimate-3-phosphate (EPSP)

synthase

• EPSP inhibition depletes

• aromatic amino acids tryptophan, tyrosine, and phenylalanine

• All needed for protein synthesis or biosynthetic pathways leading

to plant growth

• Symptomology:

• Foliar chlorosis and necrosis within 4-7 days for highly

susceptible plants and within 10-20 days for less

susceptible plants.

• Chlorosis 1st in immature leaves and growing points.

Glyphosate

• Absorption and translocation:• Moderately absorbed through cuticle. WHY NIS IS NEEDED!

• Symplast translocation with accumulation in

• Underground tissues

• Immature tissues

• Meristems

• Behavior in soil

• Rapidly and tightly absorbed to soil

• No soil-activity

• Degraded microbially in soil and water

Glufosinate

• Mode of action:

• Inhibits glutamine synthetase and production of glutamine

• Glutamine synthetase inhibition

• Affects the enzyme that converts glutamate and ammonia to

glutamine

• Accumulation of ammonia destroys cells and inhibits photosystem • Accumulation of ammonia destroys cells and inhibits photosystem

I and II reactions.

• Ammonia reduces the pH gradient across the cell membrane when

can uncouple photoposphorylation.

• Symptomology:

• Chlorosis and wilting within 3-5 days. Necrosis in 7-14

days. Rate of symptoms increased by bright sunlight, high

humidity, and moist soil.

Glufosinate

• Absorption and translocation:• Requires a 6 hour rain-free period for max activity

• Xylem or phloem movement limited

• Behavior in soil

• Weakly absorbed to soil• Weakly absorbed to soil

• No soil-activity

• Degraded rapidly microbially in soil and water

Compare MOA’s

• GLYPHOSATE• Inhibits amino acid

biosynthesis

• Chlorosis and necrosis 10-20

days

• Symptoms seen in

• Immature leaves

• GLUFOSINATE• Inhibits glutamine synthetase

activity with ammonia build-

up

• Chlorosis and necrosis 3 to 14

days

• Symptoms seen in• Immature leaves

• Growing points

• Good absorption and

translocation

• Symptoms seen in

• Foliage primarily

• Poor absorption and

translocation

paraquat

No absorption/translocation

What it touches, it hurts

glyphosate

absorption/translocation needed

to kill the plant

glufosinate

Little to no A&T. Coverage crucial.

Works better with high temps and humidity

glyphosate

glufosinate

paraquat

RR vs. LL Soybean• Amounts of herbicide

• Glyphosate

• Soybean cracking to R2 = 2.25 lb ae/A

• 3 applications of 22 oz/A of Roundup PowerMax or 32 oz/A of a generic 4 lb glyphosate

• Maximum in-crop application = 1.54 lb ae/A

• 44 oz/A of Roundup PowerMax or 66 oz/A of generic 4 lb glyphosate

• Glufosinate

• Limited to # of applications

• 2, 22 oz/A applications of Ignite = total/year of 44 oz/A/year

• 1, 29-36 oz/A application = total/year of 36 oz/A/year

• Difference?

• Greater rate and # of glyphosate applications available – RESISTANCE!

• Have to utilize additional herbicides besides Ignite because of limitation in

rate and # of applications.

RR vs. LL Soybean Research

St. Joseph, LA – Northeast Res. Station

• 2 x 3 x 3 factorial arranged in a randomized complete block

design

• 4 replications

Alexandria, LA – Dean Lee REC

RR vs. LL Soybean Research

Trial Information

Roundup Ready variety Pioneer 94M80

Liberty Link variety S080120

Seeding rate 123,500 seed/Acre

Planting date April 30th

Emergence date May 4th

Row spacing 38-in single-row

Harvest date August 9th

RR vs. LL Soybean Research• Factor 1 – Soybean variety/herbicide tolerance trait:

– Roundup Ready (Roundup PowerMax @ 22 oz/A)

– Liberty Link (Ignite @ 22 oz/A)

• Factor 2 – timing of 1st application:

– 10 d after emergence DAE– 10 d after emergence DAE

– 15 DAE

– 20 DAE

• Factor 3 – timing of sequential application:

– 10 d after 1st application (DA 1st applic.)

– 15 DA 1st applic.

– 20 DA 1st applic.

barnyardgrass

At harvest – Variety x 1st applic. timing

AA A

B

C

D

goosegrass


A A A

B

C

D

Palmer amaranth


A A A

B

C

D

entireleaf morningglory


A A AABB

C

Soybean yield

A

B

glyphosate 10 DAE fb 20 DAE



glufosinate 10 DAE fb 20 DAE



Photo taken July 7th







Photo taken July 7th

Summary• Barnyardgrass, goosegrass, and Palmer amaranth

– Control equal for 10, 15, or 20 DAE 1st application of glyphosate

– In Liberty Link soybean, make 1st application 10 DAE

• Entireleaf morningglory

– Control equal for all 1st application timings of glyphosate– Control equal for all 1 application timings of glyphosate

– 10 = 15 DAE > 20 DAE with glufosinate

• Soybean yield

– No herbicide application timing effect

– Roundup Ready variety > Liberty Link variety

– Amount of grass = amount of soybean entering combine at harvest

• HARVEST EFFICIENCY!!!!!!

Co-application with Ignite 17 DAT

St. Joseph, LA – barnyardgrass

42 DA sequential application

ab

a

bcbc a

a aa a

cbcbc

dc

b b b

a

St. Joseph, LA – tall morningglory

42 DA sequential applicaton

ab

c

d

a

bca

bc

a

cdd

ab b

bcd

dd bcd

St. Joseph, LA – 42 DA sequential

application

• hemp sesbania and redroot pigweed

–All treatments provided >95% control.–All treatments provided >95% control.

–No differences among any factors.

St. Joseph, LA – Soybean yield

b

aa

a

b

b

Weed Mgnt. in Narrow-Row Crops

• Weed control greater when soybean seeded in 19- to 51-cm

rows compared to 76-cm rows (De Bruin and Pederson 2008; Ethridge et al. 1989;

Hock et al. 2006; Knezevic et al. 2003)

• Required weed-free period for maximum yields was 4 to 8 wk

less for cotton seeded in 53-cm rows compared to 79- and less for cotton seeded in 53-cm rows compared to 79- and

106-cm rows (Rogers et al. 1976)

Considerations & Objective

• Soybean planting pattern in Louisiana varies from 19- to 102-

cm.

• Limited to two applications of glufosinate in soybean in

Louisiana.Louisiana.

• Can reducing the soybean row spacing allow a producer to

delay their sequential application of glufosinate?

Materials and Methods

• 4 x 5 factorial arranged in a randomized complete block with 4 replications

• Factor 1: Planting pattern

• 7.5-in, 15-in, 38-in single-row, and 38 in twin-row

• Factor 2: Ignite application (22 oz/A) timing

• Nontreated• Nontreated

• 10 DAE

• 10 fb 20 DAE

• 10 fb 30 DAE

• 10 fb 40 DAE

• All treatments applied with a tractor-mounted compressed air sprayer with

flatfan nozzles calibrated to deliver 15 gpa at 37 psi.

Sequential applications

Barnyardgrass, Browntop Millet, Goosegrass

42 d after sequential application

LSD (0.05) = 6

Palmer amaranth


LSD (0.05) = 11

What about PRE’s?

• Investigated:

– Authority MTZ

– Boundary

– Prefix

– Metribuzin 75 DF– Metribuzin 75 DF

– Valor SX

– Etc……..

• Which one should you use in RR or LL soybean?

– Strengths and weakness of PRE and POST system need to

be matched!

PRE herbicides in soybean

14-21 DAT

What about PRE’s?

• Glyphosate– Strong on grass & most broadleaves

– Weaker on mg’s, spod, sesbania

– RESISTANCE!

• PRE’s that provide

broadleaf control

and mitigate Res.

• Glufosinate

– Strong on broadleaf weeds

– Weaker on grass and pigweeds

– Limited # of applications

• PRE’s that provide

grass and broadleaf

control to extend

applic. window.

Entireleaf morningglory, Hophornbeam copperleaf,

& Sicklepod


EMG & HBCL

LSD (0.05) = 2

Spod

LSD (0.05) = 3

Summary• In Roundup Ready soybean

– 1st application 15-20 DAE

– Sequential application 10 to 20 DA 1st application

• In Liberty Link soybean

– 1st application 10 DAE– 1 application 10 DAE

– Sequential application 10 to 15 DA 1st application

• Addition of Flexstar to Ignite will help on grasses and pigweed

• Grass and pigweed still tough in narrow-row LL soybean

• Match PRE and POST systems!

Summary• barnyardgrass, browntop millet, and goosegrass

• Little differences between planting patterns

• Sequential applications needed

• In general, control decreased with increasing sequential DAE

• Palmer amaranth

• With one application (10 DAE) wide-rows > narrow-rows

• Sequential application at 20 DAE > 30 > 40

My advice. Know what your

getting into.

THANKS & QUESTIONS?

• Thanks to the Louisiana Soybean and Feed Grain

Research and Promotion Board for funding this research.

• Daniel Stephenson

– Dean Lee - Alexandria

– Cell: (318) 308-7225

– Office: (318) 473-6590

– Email: [email protected]

roundup ready vs. liberty link soybeans crops - daniel stephenson...harvest date august 9 th. ......

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