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Threshold vs. adjusted dosage Svend Christensen and Torben Heisel, DIAS Mark Paice SRI. Blackgrass ( Alopercurus myosuroides ). Old Seed Bank. Stochastic Germination. Plants germinating. Stochastic Seed Mortality. Dose- response. Plants surviving. Crop Weed Competition. Crop Weed
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Threshold vs. adjusted dosageSvend Christensen and Torben Heisel, DIASMark Paice SRI
Old Seed Bank Stochastic Germination Plants germinating Stochastic Seed Mortality Dose- response Plants surviving Crop Weed Competition Crop Weed Competition Seed Production and Dispersal New Seeds Yield Loss Economic Model Cost New Seed Bank Herbicide - use Stochastic Weed Control Stochastic Seed Mortality
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
Year 0 Seeds/m2 20 m
Year 1 Year 3 Seeds/m2 Seeds/m2 Year 5 Year 7 Seeds/m2 Seeds/m2 The Threshold Algorithm
Year 1 Year 3 Seeds/m2 Seeds/m2 Year 5 Year 7 Seeds/m2 Seeds/m2 PC-Plant Protection
Year 1 Seeds/m2 Year 3 Year 5 Year 7 Seeds/m2 Seeds/m2 Seeds/m2 Decision algorithm for Patch Spraying
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