Western Australian grains scientists are looking to improve weed management following soil amelioration, with new research focusing on pre-emergent herbicides.
The work is part of a broader project to examine improving farming system profitability following soil amelioration, which has investment from the Department of Primary Industries and Regional Development (DPIRD) and Grains Research and Development Corporation (GRDC).
DPIRD research scientist Arslan Peerzada said strategic deep tillage with deep ripping, rotary spading or mouldboard plough was increasingly used to ameliorate soil constraints and improve crop production.
“Previous research has demonstrated that strategic deep tillage can increase the efficacy of pre-emergent herbicides, but we have not evaluated how that may improve the management of economically damaging weeds such as ryegrass, wild radish and brome,” Dr Peerzada said.
“This study aims to highlight the importance of an integrated weed management program that can improve crop yield and promote a sustainable agricultural system.”
A research update will be delivered at the Liebe Group’s field day at Wongan Hills on Wednesday 13 September 2023.
“We have selected a range of pre-emergent herbicides that we believe will minimise crop damage after these amelioration techniques,” Dr Peerzada said.
“However, their ability to control weeds is variable and depends on the paddock situation – especially the soil moisture at the time of amelioration, as well as the depth to which weed seeds are buried through the tillage implements.
“The best solution is to avoid placing heavy reliance solely on pre-emergent herbicides in the year following strategic deep tillage.
“Growers will need to consider diversifying weed control approaches, such as in-crop herbicide application, to maximise the effectiveness of strategic tillage in terms of suppressing weed populations.”
Trial sites at Merredin and Wongan Hills are comparing the efficacy of pre-emergent herbicides in controlling grass and broadleaf weeds under four treatments – spading, deep ripping, soil inversion and no amelioration.
Eight sub-plot treatments using a range of pre-emergent herbicides have been applied at each site.
The trials are also evaluating crop phytotoxicity associated with herbicide application in altered soil conditions, along with analysing the horizontal and vertical movement of weed seeds and surface soil in response to soil inversion, deep ripping, and spading.
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