Roundup Ready vs. Liberty Link Soybeans Crops - Daniel... · • Ammonia reduces the pH gradient...

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

At harvest – Variety x 1st applic. timing

A A A

B

C

D

Palmer amaranth

At harvest – Variety x 1st applic. timing

A A A

B

C

D

entireleaf morningglory

At harvest – Variety x 1st applic. timing

A A AABB

C

Soybean yield

A

B

glyphosate 10 DAE fb 20 DAE

glyphosate 10 DAE fb 25 DAE

glyphosate 10 DAE fb 30 DAE

glufosinate 10 DAE fb 20 DAE

glufosinate 10 DAE fb 25 DAE

glufosinate 10 DAE fb 30 DAE

Photo taken July 7th

glyphosate 20 DAE fb 30 DAE

glyphosate 20 DAE fb 35 DAE

glyphosate 20 DAE fb 40 DAE

glufosinate 20 DAE fb 30 DAE

glufosinate 20 DAE fb 35 DAE

glufosinate 20 DAE fb 40 DAE

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

42 d after sequential application

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

42 d after sequential application

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: dstephenson@agcenter.lsu.edu