Investigating double break (or stacked rotation) options for weed & disease control


Research organisaton
Funding source

Trial details

Researcher(s) Chris Wilkins &, Nathan Craig West Midlands Group
Year(s) 2016
Contributor West Midlands Group
Trial location(s) Site 6, Merredin, WA
Investigating double break (or stacked rotation) options for weed & disease control locations

Including break crops into rotations with cereals can influence the nitrogen (N) dynamics of cropping systems and assist in the management of weeds and reduce disease incidence in crop rotations. Previous studies into single year break crops where herbicide-resistant annual ryegrass was present found that weeds still had a significant impact on wheat production. Interestingly, these trials demonstrated that clean fallow or break crops can deliver cheaper, more effective ryegrass control compared with in-crop grass management options in wheat.

Two break crops in a row has seen cereal yields double and grassy weeds drop in problem paddocks in low rainfall zones across South Australia. Pastures and break crops - such as pulses, canola, brown manure vetch and oaten hay – have been grown for up to two seasons and some of the results were outstanding. Despite very strong wheat yields in the first two years of the trial, disease and grassy weeds are now starting to reduce performance of continuous wheat. However, wheat following two year breaks are now producing gross margins several hundreds of dollars per hectare better than continuous wheat with no major constraints developing yet. One year breaks have improved the following wheat performance, but weeds and diseases are still present.

The main objective of this project is to demonstrate the rotational benefits of a sequence of broadleaf, legume, and pasture crops for the production of wheat in the Kwinana West and East zones of WA.

Key messages

The results presented in this report are from the first year of a three-year study that investigates the effect of break-crop sequences on wheat grain yield. The site was selected due to its high background levels of ryegrass control, and crop rotation treatments have been designed around weed control as the main rotational factor.

Grain yield was relatively low compared to the growing season rainfall of 253 mm. Grain yield was affected by severe frost that occurred during grain fill.

This project will continue with the second crop in rotation for the 2017 season, followed by wheat across all plots in 2018 to assess the benefit of a stacked rotation for subsequent wheat grain yield.

Lead research organisation West Midlands Group
Host research organisation West Midlands Group
Trial funding source GRDC WMG00003-A
Related program N/A
Acknowledgments N/A
Other trial partners GRDC
Download the trial report to view additional trial information


Crop type
Treatment type(s)
  • Crop: Rotation
Trial type Experimental
Trial design Unknown

Merredin 2016

Sow rate or Target density 100kg/ha
Sowing machinery

Knifepoint & presswheel 

Sow date 27 May 2016
Harvest date 18 November 2016
Plot size 2.88m x 12m
Plot replication 4
Fertiliser <p>Summit Gusto&nbsp;(10N:12P:14K:7.5S + 0.5CU +0.1Zn) @ 80 kg/ha</p>
Seed treatment Raxil® Pro
Download the trial report to view additional method/treatment information
Trial source data and summary not available
Check the trial report PDF for trial results.
Observed trial site soil information
Trial site soil testing
Not specified
Soil conditions
Trial site Soil texture
Site 6, Merredin, WA Sand to sandy loam
Derived trial site soil information
Australian Soil Classification Source
Trial site Soil order
Site 6, Merredin, WA Sodosol
National soil grid Source
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.

Site 6, Merredin WA


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

SILO weather estimates sourced from
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.