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