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Weed germination in the field - can it be predicted?

Weed germination in the field - can it be predicted?. Ilse A. Rasmussen, DIAS Jesper Rasmussen, DAU. Weed germination in the field. Registrations Results analysis using ”Weed Cast” Discussion. Locations of registrations. Registrations. 3 years Weeds counted in spring barley fields

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Weed germination in the field - can it be predicted?

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  1. Weed germination in the field - can it be predicted? Ilse A. Rasmussen, DIAS Jesper Rasmussen, DAU

  2. Weed germination in the field • Registrations • Results • analysis • using ”Weed Cast” • Discussion

  3. Locations of registrations

  4. Registrations • 3 years • Weeds counted in spring barley fields • 20 counts in each field 1 m apart • at most 20 m between counts • 1 - 2 times per week • Number of most occurring species • same plot every count • Largest growth stage of each species

  5. Results • Climate from nearby stations • Either • mean of all counts in one field • or split into 4 ”plots” of 5 counts • Results from different fields where the same weed species were present

  6. Germination of POLCO Plant number Day R2 = 97.5 t R2 = 98.2 Number of POLCO emerged in relation to temperaturesum or days Mean of 20 counts in one field

  7. Germination of POLCO • Temperature sum or number of days equally well suited for modelling emergence

  8. Germination of POLCO t Day Percentage of POLCO emerged in 5 different fields April 1st: t = 0 and Day = 0 t: temperature sum (base 0)

  9. Germination of POLCO • Different sowing times, climate etc. • Up to 100 day-degrees difference of 50% germination • Up to 14 days difference of 50% germination • 100% germination app. the same • Different slopes of the germination curve

  10. Germination of CHEAL Germination of CHEAL in 4 plots in one field. 5 counts carried out in each plot. Largest distance between counts: 20 m

  11. Prediction of germination • If these models are general, it will be possible to predict • when 50% of the weeds have emerged • how large the total emergence will be • The slope of the germination curves are different • between fields • between plots in one field

  12. Relationship between germination of different species Germination of TRIIN and VIOAR in relation to POLCO in 3 different fields

  13. Relationship between germination of species • If germination was dependent only upon external input, the relationship between two species should be the same on all locations • As this is not so, it seems that factors within the seeds interacted with the environment to give different germation curves

  14. What do we need to do? • Field monitoring? • Lab or semi-field research? • Can it be done at all?

  15. Germination of POLCO - actual and prediction by WEEDCAST

  16. Germination of POLCO - actual and prediction by WEEDCAST

  17. Germination of CHEAL - actual and prediction by WEEDCAST

  18. How do we fit the models? • Base-temperature • Soil types • Soil moisture threshold

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