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Phase rethink to aid weed and pest management

Dr Yaseen Khalil from the Australian Herbicide Resistance Initiative (AHRI) at the University of Western Australia is investigating whether disruptive pasture sequences could provide opportunities to improve weed and soil-borne disease management in Western Australian cropping systems.
Photo: Evan Collis

Crop rotation is an age-old practice to minimise pests and diseases, reduce chemical use, aid in building and maintaining healthy soil, and manage nutrient requirements – all of which maximise yield potential. But to ensure that Australian farming systems continue to improve their profitability and durability, a new lens is being focused on crop sequences.

Dr Yaseen Khalil is quantifying the agronomic and economic benefits of disruptive pasture phases as part of a capacity-building project through GRDC-investment with the Australian Herbicide Research Initiative (AHRI) at the University of Western Australia (UWA).

“I grew up working on my family farm in north-east Syria, where I developed a fascination for agriculture and food production,” Dr Khalil says.

It led him to complete a bachelor’s degree in agriculture in 2007 and master’s degree in the history of applied science in 2012 at the University of Aleppo in Syria.

He joined the International Center for Agricultural Research in the Dry Areas (ICARDA) in 2007 and spent seven years disseminating conservation agriculture information in Iraq and Syria on a project funded by the Australian Centre for International Agricultural Research (ACIAR).

Trial establishment, measurements of soil, crop, weed and pest parameters, and data analysis were major components of this work. I also gained valuable skills in coordinating farmer surveys investigating zero-tillage adoption in Syria and contributed to grower workshops to improve adoption and development of local zero-tillage seeders.

He won an ACIAR/John Allwright Fellowship, funded by AusAID, to undertake his PhD on the interaction between pre-emergent herbicides and crop residues in no-till farming systems in Western Australia. He moved to Australia in 2014, completing the PhD in 2018, and started work on the GRDC-supported postdoctoral project in 2019.

Benchmark grower survey

Dr Khalil’s work involves several facets but it was started with a foundational survey with cooperating AHRI farmers across the WA wheatbelt to compare paddock management by growers using pasture phases, with growers who operated with little rotational diversity. Seedbank evaluation on these selected farms helped to quantify the effectiveness of management methods using disruptive pasture phases in achieving low weed seed banks.

Directed by the survey, a serradella and weed control focus site was established at the UWA farm at Pingelly to evaluate weed control management options – singularly and in combinations – in reducing weed seedbanks in serradella phases.

The French serradella variety Cadiz was selected as the pasture species because, in addition to its ability to fix nitrogen, it has been shown to reduce root lesion nematode in subsequent cereal crops, as well as other soil-borne crop pathogens. It is low-cost to establish and specifically developed for use in phases to be directly harvested for seed, grazed or used as silage.

Siting the trial at the UWA farm meant animals could graze the trials. Two additional sites were established at Bolgart and Brookton to focus on the impact of serradella phases in minimising weed seed-set in crop rotations, primarily focused on ryegrass. The serradella pasture phases where one, two or three years in duration.

“From the university farm site, we concluded that although single weed management tactics were not effective in providing weed number reduction early in the growing season, some of them – weed wiping, spray-topping, mowing and spray-topping, hay/silage production, green manuring, brown manuring – applied at full canopy stage were very effective in reducing weed seed production,” Dr Khalil says.

Analyses to determine effects on disease levels and the economics of the rotations will be carried out at the end of the rotations.

Dr Khalil is keen to pursue his interest in developing robust farming systems for Australia. He is especially interested in farming systems and reintegrating pastures into Australian cropping rotations.

More information: Dr Yaseen Khalil, 0449 880 461,

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