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Spatial and Population Dynamics of Patches
of Wild-oats
Nicola Perry and Peter Lutman
IACR-Rothamsted
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Background:
• Important grass weed
• Patchy distribution
• Patch stability unknown
Wild-oats:
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Experiment details
• Patch size 3x3 m
• Two sowing densities:– 10 plants/m2 and 50 plants/m2
• Ploughing, cultivations and combining in same direction each year
• +/- wild-oat herbicide in 2000
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Experiment design
SLD
SHDLDSHD
LDSLDHD
HD
HD = high density; LD = low density; S = sprayed
arrows indicate cultivation & combining direction
N
30m
12m
3m
3m
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Monitoring
• Panicle distribution
• Seed movement
• Patch shape
• Location of outliers
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Panicle and seed distribution 1999
Panicles / m2
Seeds / m2
0
5
10
15
20
25
30
35
40
-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Distance (m)
Pa
nic
les
/ m
2
0
200
400
600
800
1000
1200
1400
Se
ed
s /
m2
Direction of cultivation & combining
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Panicle and seed distribution Sprayed Treatments 2000
Panicles / m2
Seeds / m2
0
20
40
60
80
100
120
-6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24
Distance (m)
Pa
nic
les
/ m
2
0
500
1000
1500
2000
2500
3000
3500
Se
ed
s /
m2
Direction of cultivation & combining
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Seed distribution after harvestSprayed v Unsprayed 2000
0
2
4
6
8
10
12
14
16
18
-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24
Distance (m)
Pe
rce
nta
ge
of
tota
l s
ee
ds
Sprayed UnsprayedDirection of cultivation & combining
Total no. seeds/m2
Sprayed: 17,860
Unsprayed: 139,410
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Low Density Sprayed Patch
1998 (9 m2)
1999 (20.3 m2)
2000 (20.6 m2)m
harvesting &
cultivation
0 1 2 3
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m
1998 (9 m2)
1999 (29.5 m2)
2000 (41.0 m2)
High Density Unsprayed Patch
harvesting &
cultivation
0 1 2 3
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513260 513280 513300213180
213190
213200
213210
213220
213230
213240
213250
213260
213270 1999
Patch outline
Outliers
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513260 513280 513300 513320213180
213190
213200
213210
213220
213230
213240
213250
213260
213270
213280
2000
Patch outline
OutliersS
S
S
S
S Sprayed plots
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Conclusions
• Majority of seeds move 1-2 m– movement due to cultivations and plants
leaning in wind
• Isolated plants occur up to 30 m away– movement by combine– may lead to future infestations / new
patches
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Conclusions
• Wild-oats need frequent re-mapping
• Patches not stable and new patches may form from isolated plants
• Presence of outliers make decisions on patch spraying complicated
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Limitations of manually mapping
weed patches
Nicola Perry and Peter Lutman
IACR-Rothamsted
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Methods of manually mapping weed patches
• Visual detection (human)– mapping on a grid– ATV, tractor/sprayer, combine– walking around patches
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Weed attributes which can be recorded
• Presence / absence
• Approximate levels (high / low)
• Weed numbers
• Weed vigour / ground cover
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Weed attributes which can be recorded from a vehicle or using quadrats
Vehicle Quadrat
Presence/Absence
Levels (high/low) ?
Counts x
% cover x
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Timing of visual assessments
Winter EarlySpring
Summer Harvest
Black-grass
? Y Y N
Cleavers ? Y Y ?
Wild-oats ? ? Y Y
Couchgrass
N N ? Y
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Activities on Warren Field(winter wheat)
Crop drilled 16 Sept 99
Quadrat mapped 2 Dec 99
ATV mapped 27 Jan 00
Sprayed ‘Grasp’ 13 Mar 00
Sprayed ‘Topik’ 30 Apr 00
Tractor mapped 30 Jun 00
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Warren Field black-grass comparison of mapping methods
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
Correlation : 0.82
Quadrat threshold 20 plants/m2 (Dec 99)
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
Black-grass
No Black-grass
ATV (Jan 00)
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Warren Field black-grass comparison of mapping methods
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
Correlation : 0.60
Quadrat threshold 5 plants/m2 (Dec 99)
Black-grass
No Black-grass
ATV (Jan 00)
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
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Warren Field black-grass comparison of mapping methods
Correlation : 0.37
Quadrat threshold 20 plants/m2 (Dec 99)
Black-grass
No Black-grass
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
Tractor (June 00)
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Warren Field black-grass comparison of mapping methods
Correlation : 0.84
Quadrat threshold 2 plants/m2 (Dec 99)
Black-grass
No Black-grass
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
Tractor (June 00)
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Warren Field wild-oats comparison of mapping methods
ATV (Jan 00)
Correlation : 0.74
Quadrat threshold 2 plants/m2 (Dec 99)
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
Wild-oats
No Wild-oats
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Warren Field wild-oats comparison of mapping methods
Tractor (June 00)
Correlation : 0.58
Quadrat threshold 2 plants/m2 (Dec 99)
Wild-oats
No Wild-oats
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
80
90
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Broad Mead black-grass comparison of mapping methods
ATV (Jan 00)
Correlation : 0.70
Quadrat threshold 5 plants/m2 (Dec 99)
Black-grass
No Black-grass0 20 40 600
20
40
60
80
100
120
140
0 20 40 600
20
40
60
80
100
120
140
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Black-grass distribution in Cashmore Field
Mapped from ATV Nov 99
Mapped from combine July 00
black-grass
no black-grass
508450 508500 508550 508600 508650 508700 508750
235450
235500
235550
508500 508550 508600 508650 508700 508750
235450
235500
235550
508450 508500 508550 508600 508650 508700 508750
235450
235500
235550
Mapped on foot May 00
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Conclusions
• Limitations to manually mapping weeds
• Discrete quadrat sampling too time consuming for mapping on a whole-field scale
• Continuous visual detection from a vehicle is less accurate, & may be restricted to tramlines, but is quicker
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Conclusions
• Need to make more progress with optimum visual detection in absence of automated detection