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United States Department of Agriculture

Agricultural Research Service

Title: WEED SEEDLING EMERGENCE MODELLING: CONVERTING OBSERVATIONS INTO EQUATIONS FOR WEEDEM

Author
item Forcella, Frank
item Walsh, Michael
item Archer, David
item Peltzer, Sally
item Cousens, Roger
item Chapman, Ross
item Gallagher, Robert
item Powles, Stephen

Submitted to: Australian Weed Science Society Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/13/2002
Publication Date: 9/13/2002
Citation: FORCELLA, F., WALSH, M., ARCHER, D.W., PELTZER, S., COUSENS, R., CHAPMAN, R., GALLAGHER, R., POWLES, S. WEED SEEDLING EMERGENCE MODELLING: CONVERTING OBSERVATIONS INTO EQUATIONS FOR WEEDEM. JACOB, H.S., DODD, J., MOORE, J.H, EDITORS. WEEDS: THREATS NOW AND FOREVER? 13TH AUSTRALIAN WEED SCIENCE SOCIETY PAPERS AND PROCEEDINGS. 2002. P. 260.

Interpretive Summary:

Technical Abstract: The timing and extent of weed seedling emergence are critical variables for successful weed management in arable crops. Although observations of the timing and extent of weed seedling emergence have been reported often, our abilities to predict these variables have not progressed as rapidly as needed to take full advantage of modern control technologies. Data sets for annual ryegrass were obtained from NSW, SA, VIC, and WA, whereas those for wild radish were from VIC and WA. In all cases data on seedling densities were collected periodically during the growing season, which allowed study of emergence timing and calculation of cumulative emergence over time. The densities of seeds in the soil were recorded in some studies. These latter data, when combined with densities of emerged seedlings, allowed calculation of percentage of seedbank that emerged, thereby allowing exploration of seed dormancy relationships with microclimate. Daily soil temperatures and water potentials were recorded at some sites and estimated for the remainder of sites. Then these data were combined to form an index of hydrothermal time, which was related to seed dormancy status and extent and timing of seedling emergence for each species. Although more research will be necessary to adjust these hydrothermal-based models, especially soil microclimate estimates, at this time the broad aspects of the timing and extent of seedling emergence of annual ryegrass and wild radish appear predictable.

Last Modified: 07/26/2017
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