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 t R2 = 97.5 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