Threshold vs. adjusted dosage
Svend Christensen and Torben Heisel, DIASMark Paice SRI
Blackgrass (Alopercurus myosuroides)
Old Seed Bank
Plants germinating
Herbicide -use
StochasticSeed Mortality
New SeedBank
Cost
StochasticGermination
Economic Model
Yield Loss
StochasticWeed Control
Plants surviving
Crop WeedCompetition
Seed Productionand Dispersal
Stochastic Seed
Mortality
Dose- response
New Seeds
Crop WeedCompetition
Initial Blackgrass Data
• Blackgrass density was measured in a 14 m x 14 m grid in a winter barley at Silsoe Research Institute
• The model unit was 1 m by 1 m cells
• Treatment unit was 4 m by 4 m cells
Spatial weed management of Blackgrass
• The threshold algorithm• PC-Plant Protection• DAPS (Decision Algorithm for Patch
Spraying)
The Threshold Algorithm
If Blackgrass density was higher than 1 plant m-2
A normal dose of 3.5 l ha-1 IPU was applied
PC-Plant Protection
A normal dose of 2.1l ha-1 IPU was applied
Input data Output data
Point or zone model
Competition model
PC-Plant Protection
Decision model
DAPS - Decision Algorithm for Patch Spraying
ResultsSeed Bank
Seeds/m2Year 02
0 m
The Threshold Algorithm
Seed
s/m2
Year 1
Seed
s/m2
Year 5
Seed
s/m2
Year 3S
eed
s/m2
Year 7
PC-Plant Protection
Seed
s/m2
Year 5
Year 1 Seed
s/m2
Seed
s/m2
Year 3S
eed
s/m2
Year 7
Decision algorithm for Patch Spraying
Seed
s/m2
Year 1
Year 3 Seed
s/m2
Seed
s/m2
Year 5 Seed
s/m2
Year 7
Yield loss (DKK ha-1)
Year Threshold PC-P DAPS
1 171 207 38
2 175 195 16
3 184 186 18
4 190 177 17
5 196 168 17
6 197 161 17
7 204 153 17
1317 1247 140
IPU dose (l ha-1)
Year Threshold PC-P DAPS
1 1.7 2.1 2.8
2 2.1 2.1 2.3
3 2.2 2.1 2.1
4 2.3 2.1 1.9
5 2.3 2.1 1.7
6 2.4 2.1 1.7
7 2.4 2.1 1.7
15.4 14.7 14.2
Cost (DKK ha-1)
Year Threshold PC-P DAPS
1 77 91 123
2 92 91 99
3 97 91 93
4 99 91 82
5 101 91 78
6 106 91 75
7 105 91 75
677 637 625
Model Assumptions
• The size of the treatment area affects the differences between the algorithm
• No spatially or temporally depended effect of soil conditions or cultivation factors on seed emergence, crop weed competition or seed production
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