1 Mechanical Weed Control in Organic Crops Eric N. Johnson 1 and Steven J. Shirtliffe 1 Agriculture and Agri-Food Canada, Scott, SK 2 EWRS 3 Hand weeding intra-row weeds: 200-500 hours per hectare in carrot and direct sown onion and leek DIAS 4 Mechanical Weed Control Research in Saskatchewan • Pre-seeding tillage • Pre-emergence tillage – Rod-weeder, harrow, rotary hoe, small shovels on heavy harrow • Post-emergence – Harrows, rotary hoe – Inter-row cultivation – Mowing, rolling, weed clipping – Alternative cropping study – long-term study 5 6 Pre-seeding tillage
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Mechanical Weed Control in Organic Crops...1 Mechanical Weed Control in Organic Crops Eric N. Johnson1 and Steven J. Shirtliffe 1Agriculture and Agri-Food Canada, Scott, SK 2 EWRS
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1
Mechanical Weed Control in Organic Crops
Eric N. Johnson1 and Steven J. Shirtliffe1Agriculture and Agri-Food Canada, Scott, SK
2
EWRS
3
Hand weeding intra-row weeds:
200-500 hours per hectare in carrot and direct sown onion and leek
DIAS
4
Mechanical Weed Control Research in Saskatchewan
• Pre-seeding tillage• Pre-emergence tillage
– Rod-weeder, harrow, rotary hoe, small shovels on heavy harrow
• Post-emergence – Harrows, rotary hoe– Inter-row cultivation– Mowing, rolling, weed clipping– Alternative cropping study – long-term study
5 6
Pre-seeding tillage
2
7
Interaction of Seed Date and Flax Cultivar on Yield. Mean of 2 sites (Saskatoon, Scott). 2003
0200400600800
10001200140016001800
May 15 June 1 June 15
Seed Date
kg h
a-1
BethuneVimyNormandyLine 6Line 5
Seed Date X Cultivar interactionp < 0.01
8
Effect of seeding date and weed management on weed biomass in flax. Scott and Saskatoon, SK 2003-2005.
Effect of seeding date and weed management on yield of flax. Scott and Saskatoon, SK 2003-2005.
~70%
10
Post-seeding / Pre-emergenceTillage in field pea
MECHANICAL WEED CONTROL RESEARCH IN SASKATCHEWAN
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Questions
• Seed shallow and compete ??• Seed deep / pre-emerge till ??• Seed early?? Seed late ??
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Interaction of Seeding Date, Seed Depth/Tillage System on Weed Biomass in Field Pea. Scott 1999-2001.
0100200300400500600700800900
1000
Wd
biom
ass
(g/m
2)
Check Harrow Rod Wd
Early May
HerbicideEarly
2.5 7.5 2.5 7.5 2.5 7.5Mid May Late May
3
13
Effect of Seeding Date, Seed Depth/Tillage System on Field Pea Yield. Scott 1999-2001.
0
500
1000
1500
2000
2500
3000
3500
Yiel
d (k
g/ha
)
Check Harrow Rod Wd
Early May2.5 7.5 2.5 7.5 2.5 7.5
Mid May Late May
HerbicideEarly
14
Field pea seeded May 4 3” depth - Herbicide
Field pea seeded May 18 3” depth - Pre-emergence rod-
weed
If timed properly, pre-emergence tillage can be effectivein large seeded crops
•The best seed date X seed depth/pre-emergence tillage combination resulted in 80% of the yield obtained with the best seed date/ seed depth/ herbicide combination.
15
Maintenance ofCrop Residues
16
17 18
Effect of rotary hoe passes on the maintenance of cereal stubble residue, Scott, SK. 2004 - 06.
• Unreplicated strip trials in fallow and stubble• Stubble had moderate amounts of trash• Seeded to field pea• Treatments
– Untreated– Single Pass Till 5 DAS– Double Pass Till 5 DAS– Single Pass Till + Single Pass Rotary Hoe 5 DAS– Double Pass Rotary Hoe 5 DAS– Single Pass Till Ground Crack– Single Pass Till 3-node
24
Pre-emergence Tillage With Small Shovels – Field Pea Density Scott 2008
0102030405060708090
100
Unt
reat
ed
SP T
ill 5
DA
S
DP
Till
5 D
AS
SP T
ill, S
P R
. Hoe
5 D
AS
DP
R. H
oe 5
DA
S
SP T
ill G
. Cra
ck
SP T
ill 3
Nod
e
Plan
ts/m
2
Stubble
0102030405060708090
100
Unt
reat
ed
SP T
ill 5
DA
S
DP
Till
5 D
AS
SP T
ill, S
P R
. Hoe
5 D
AS
DP
R. H
oe 5
DA
S
SP T
ill G
. Cra
ck
SP T
ill 3
Nod
e
Fallow
5
25
Pre-emergence Tillage With Small Shovels – Field Pea Yield Scott 2008
010203040506070
Unt
reat
ed
SP T
ill 5
DA
S
DP
Till
5 D
AS
SP T
ill, S
P R
. Hoe
5 D
AS
DP
R. H
oe 5
DA
S
SP T
ill G
. Cra
ck
SP T
ill 3
Nod
e
bus/
acre
Stubble Fallow
010203040506070
Unt
reat
ed
SP T
ill 5
DA
S
DP
Till
5 D
AS
SP T
ill, S
P R
. Hoe
5 D
AS
DP
R. H
oe 5
DA
S
SP T
ill G
. Cra
ck
SP T
ill 3
Nod
e
26
Pre-emergence Tillage With Small Shovels – Field Pea Yield Scott 2008
0
10
20
30
40
50
Unt
reat
ed
SP T
ill 5
DA
S
DP
Till
5 D
AS
SP T
ill, S
P R
. Hoe
5 D
AS
DP
R. H
oe 5
DA
S
SP T
ill G
. Cra
ck
SP T
ill 3
Nod
e
% d
ocka
ge
Stubble Fallow
0
10
20
30
40
50
Unt
reat
ed
SP T
ill 5
DA
S
DP
Till
5 D
AS
SP T
ill, S
P R
. Hoe
5 D
AS
DP
R. H
oe 5
DA
S
SP T
ill G
. Cra
ck
SP T
ill 3
Nod
e
27
Tilling at 3-node stage
28
Post-emergence Tillage
29
Selectivity of Harrow Types
Tine Rotary
Flex-Tine Lely
Flex-Tine Einbock
30
Mechanical In-Crop Weed Control Selectivity
• Selectivity
– differential tolerance in plant species.
– Ratio between weed control and crop damage
• Selectivity dependent on:
– How closely weeds resemble the crop
– length of seed germination period
– ineffective - perennial weeds
6
31
Relationship between crop burial and yield of field pea from post-emergence harrowing at 3 above-ground node stage. Weedy conditions. Scott 2004 & 2006.
Effect of harrow type and disturbance level on wild oat fresh weight (g m-2), Scott, 1999
0100200300400500600
Tine Low Tine High Rotary Low RotaryHigh
Untreated
Harrow Type
g m
-2
10° back
High45° back
Low
34
Crop Tolerance to Post-Emergence Harrowing
• Crop tolerance is composed of two factors:
– Resistance: the ability of the crop to resist soil covering;
– Recovery: the ability of the crop to recover from soil covering.
35
Crop burial of barley, oat and wheat (from left to right) after four passes at the two leaf stage. Averaged over all treatments, crop burial of wheat (57%) was significantly greater (P<0.05) than barley (44%) and oat (38%).
Oat and barley had higher resistance to crop burial
than wheat
36
Effect of timing of post-emergence harrowing on crop burial – mean of oats, barley, and wheat. Scott/ Saskatoon
y = 5.8834x + 59.129R2 = 0.9318
y = 6.4145x + 17.746R2 = 0.9989
y = 2.1129x + 5.8R2 = 0.8764
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7
Number of Harrow Passes
Estim
ated
Cro
p B
uria
l (%
)
2 4 6
Leaf stage
y = 5.8834x + 59.129R2 = 0.9318
y = 6.4145x + 17.746R2 = 0.9989
y = 2.1129x + 5.8R2 = 0.8764
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7
Number of Harrow Passes
Estim
ated
Cro
p B
uria
l (%
)
2 4 6
Leaf stage
Later growth stages had higher resistance to crop
burial
7
37
Effect of post-emergence harrowing on yields of oats, barley, and wheat relative to untreated checks. Weed-free conditions.