Effect of wheat seed rate and herbicide on annual ryegrass control (Roseworthy)

Trial In Progress

CC BY 4.0

Research organisatons
Funding source

Trial details

Researcher(s) Ben Fleet
Gurjeet Gill
Contact email gurjeet.gill@adelaide.edu.au
Contact phone 0428 592825
Year(s) 2022
Contributor School of Agriculture, Food and Wine - The University of Adelaide
Trial location(s) Roseworthy campus, University of Adelaide, SA
Effect of wheat seed rate and herbicide on annual ryegrass control (Roseworthy) locations

This field trial at Roseworthy was undertaken to investigate factorial combinations of wheat seed rate, and herbicides packages on wheat grain yield and the management of annual ryegrass.

Key messages

Key messages
• A field trial was undertaken at Roseworthy in 2022 to investigate the effect of combinations of wheat seed rate and herbicide treatments on crop yield and annual ryegrass (ARG) control.
• The increase in wheat plant density in the range of 100 to 300 plants/m2 improved suppression of ARG seed production (17-30%) and increased wheat grain yield (15-21%). However, herbicide treatments were the major driver of wheat grain yields and ARG suppression (P<0.001).
• The trial site had a large ARG seedbank that resulted in heavy and prolonged weed establishment. This was evident from inadequate ARG control achieved with pre-emergent herbicides alone. The trial site also had a detectable level of trifluralin resistance, which would have reduced efficacy of Trifluralin + Avadex Xtra® treatment.
• The sequential application of pre-emergent herbicides followed by an early post-emergent herbicide reduced ryegrass seed set by 94% compared to the untreated control and increased wheat yield by 4.57 t/ha.
• There was an exponential relationship between nitrogen recovery by wheat and ARG seed set, which accounted for >89% of the variation. Wheat plant density and herbicides treatments had a significant influence on nitrogen recovery in grain where only 300 wheat plants/m2 recovered nitrogen equivalent to fertiliser N applied. Only herbicide treatments achieving >60% ARG suppression achieved nitrogen recovery greater or equivalent to applied fertiliser N.

Lead research organisation School of Agriculture, Food and Wine - The University of Adelaide
Host research organisation University of Adelaide
Trial funding source GRDC 9175134
Related program GRDC Crop Protection - Weeds

We thank GRDC for providing funding for this project.

Other trial partners Not specified


Crop type Cereal (Grain): Wheat
Treatment type(s)
  • Herbicide: Type
  • Sowing: Rate
Trial type Experimental
Trial design Randomised,Replicated

Roseworthy campus, University of Adelaide 2022

Sow date Not specified
Harvest date Not specified
Plot size Not specified
Plot replication Not specified
Observed trial site soil information
Trial site soil testing
Not specified
Soil conditions
Trial site Soil texture
Roseworthy campus, University of Adelaide, SA Not specified
Derived trial site soil information
Australian Soil Classification Source: ASRIS
Trial site Soil order
Roseworthy campus, University of Adelaide, SA Chromosol
National soil grid Source: CSIRO/TERN
NOTE: National Soil Grid data is aggregated information for background information on the wider area
Actual soil values can vary significantly in a small area and the trial soil tests are the most relevant data where available

Soil properties



Derived climate information

No observed climate data available for this trial.
Derived climate data is determined from trial site location and national weather sources.

Roseworthy campus, University of Adelaide SA


Some data on this site is sourced from the Bureau of Meteorology

SILO weather estimates sourced from https://www.longpaddock.qld.gov.au/silo/
Jeffrey, S.J., Carter, J.O., Moodie, K.B. and Beswick, A.R. (2001). Using spatial interpolation to construct a comprehensive archive of Australian climate data , Environmental Modelling and Software, Vol 16/4, pp 309-330. DOI: 10.1016/S1364-8152(01)00008-1.

Trial report and links

Trial last modified: 29-03-2023 13:07pm AEST