Determination of the optimal timing and number of ridgings to control ragweed

(Ambrosia artemisiifolia) in organically produced soyabean

Maryse LeblancInstitut de recherche et de développement en agroenvironnement,

Saint-Hyacinthe, Québec, Canada

Daniel Cloutier, Pierre-Antoine Gilbert

EWRS 9th Workshop : Physical and Cultural Weed ControlSamsun, Turkey

QUÉBEC (7,7 million)

Francophones

CANADA(33,7 million)

Saint-Hyacinthe

Outline• Introduction

-biology

-problematic

• Objectives

• Methodology

-modification of the inter-row weeder

• Experimental results

• Conclusion

IntroductionCOMMON RAGWEED

Ambrosia artemisiifolia L.

• Annual dicotyledonous

• Pubescent, 1.5 m high

• Monoecious (having separate male flowers and female flowers on the same plant)

• Indigenous in Canada

• 3000 seeds/plant

• Some seeds remain viable for 40 years (usually 10-12 years)

Problematic• Cause respiratory allergies that

affect 10-15% of the population

ProblematicA few plants on row

escape cultivations and:• Continue to grow

• Become higher than soyabean

• Flower and produce pollen = allergies

• Produce viable seeds which fall down on soil and increase weed seed bank

• Make harvesting difficult and decrease seed quality

• Stain soyabean seeds because ragweed plants are still green at harvest time

Objectives• Determine the effect of ridging on ragweed

control and soyabean yield

• Determine the optimal timing to build the ridge

• Determine the effect of ridging once compared with ridging two, three or four times

Methodology• Soil type: Clay loam

• Preceding crop: Soyabean

• Fertilization: None

• Soyabean variety: S10-B7

• Seeding date: 2009: 20/5, 2010: 18/5

• Seeding rate: 517000 seeds/ha

• Seeding depth: 3,8 cm

• Row spacing: 0,76 cm

Methodology• Controls:

- Weedy check

- Hand weeded check

• Conventional cultivation (except controls):

Plots cultivated 3 x:

- 2-3 flex-tine harrowings

- 1 inter-row cultivation

Flex-tine harrow → 2-3 times • Speed: 6 km/h• Dates: 2009 2010

June 5 (cotyledons) May 27 (unifoliate)

June 14,18 (unifoliate) June 8 (1st trifoliate)

Hatzenbichler

Inter-row weeder with S-tines→ 1 x

• Speed: 7 km/h

• Dates: 2009 2010

June 22 (1st trifoliate) June 15 (2nd trifoliate)

Vicon RT 2100

2010: With harrow discs mounted to pull soil away from the row

18 cm

30 cm

Diameter: 28 cm

Harrow discs effect on soil

7,5 cm

19 cm

10 cm

Field after an inter-row cultivation with harrow discs

Methodology

• Ridging:

- 1 to 4 inter-row cultivations with hilling discs

- at 1, 2, 3 and/or 4 WALC (weeks after the last cultivation)

Inter-row cultivator with hilling discs

Diameter: 33 cm

Added weight: 5 x 37,5 kg

Ridging Speed2009 2010 1er 3,0 2/7 (4th trif.) 22/6 (4th trif.) 2e 5,8 10/7 (5th trif.) 3/7 (6th trif.) 3e 5,8 20/7 (17th trif.) 7/7 (1st side shoot)

4e 5,8 23/7 (18th trif.) 15/7 (6th side shoot)

1st: 21,6 cm2, 3, 4th: 26,7 cm

1st: 45 cm2, 3, 4th: 50 cm

12 cm

2010: discs staggered

2009: discs mounted face to face

22°

Ridge height at harvest time

• 1 ridging : 6,0 cm• 2 ridgings : 8,3 cm• 3 ridgings : 10,0 cm• 4 ridgings : 10,5 cm

Treatments (randomized complete block with 4 replications)

No Ridging WALC (week after the last cultivation)

1. 0→ Conventional cultivation

2. 1 1 3. 1 2 4. 1 3 5. 1 4 6. 2 1 & 2 7. 2 1 & 3 8. 2 1 & 4 9. 2 2 & 3 10. 2 2 & 4 11. 2 3 & 4

12. 3 1, 2 & 3 13. 3 1, 2 & 414. 3 1, 3 & 415. 3 2, 3 & 416. 4 1, 2, 3 & 417. Weedy check18. Hand weeded check

048

12162024

1 2 3 4 12 13 14 23 24 34 123 124 134 234 1234

Weeks after the last cultivation

T/ha

Ridging Weedy Handweeded no ridging

Results

2009: Ragweed biomass at harvest time

0

1

2

3

4

1 2 3 4 12 13 14 23 24 34 123 124 134 234 1234

Weeks after the last cultivation

T/ha

Ridging Weedy Handweeded No ridging

2010: Ragweed biomass at harvest time

Results

Results

Cultivation Density before (plants/m2) %

coty 2L 4L 6L +6L Control1st Flex-tine H. 55 19 0 0 0 872nd Flex-tine H. 381 6 13 7 2 76Inter-row c. 63 112 4 9 7 65with h. discs

Ragweed control after conventional cultivation in 2010(on crop row)

(Without harrow disc = 30%)

Ridging Density before (plants/m2) %coty 2L 4L 6L +6L Control

Once at:1 WALC 10 45 60 5 15 722 WALC 5 15 20 25 25 483 WALC 0 5 45 60 75 144 WALC 0 5 10 25 25 45

Several:1st @ 1 WALC 25 20 45 10 10 872nd @ 2 WALC 35 5 10 5 5 813rd @ 3 WALC 0 0 5 0 5 504th @ 4 WALC 40 0 0 0 5 25

Ragweed control after ridging in 2010Results

2009: Soyabean yield at 14 % moisture

0

1

2

3

4

1 2 3 4 12 13 14 23 24 34 123 124 134 234 1234

Weeks after the last cultivation

T/ha

Ridging Weedy Handweeded No ridging

Results

0

1

2

3

4

5

1 2 3 4 12 13 14 23 24 34 123 124 134 234 1234

Weeks after the last cultivation

T/ha

Ridging Weedy Handweeded No ridging

2010: Soyabean yield at 14 % moisture

Results

2009: Seed pod number per plant

048

1216202428

1 2 3 4 12 13 14 23 24 34 123 124 134 234 1234

Weeks after the last cultivation

Seed pods/plant

Ridging Weedy Handweeded No ridging

Results

048

1216202428

1 2 3 4 12 13 14 23 24 34 123 124 134 234 1234

Weeks after the last cultivation

seed pods/plant

Ridging Weedy Handweeded No Ridging

2010: Seed pod number per plant

Results

Conclusion

Ragweed control:

• Inter-row weeding with harrow discs decreased the number of ragweed seedlings on row crop

• If there is only one ridging, it is better to do it at 1 WALC

• It is not necessary to do more than 2 ridgings

ConclusionSoyabean:

• Soyabean yield and seed pod number were not affected by the ridging

Germain Moreau, technicianField workers from IRDA

Summer students

Financial support from MAPAQ (Programme Prime-vert, Volet 11)