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Ongoing project

A strategic approach to weed management for the Australian vegetable industry (VG15070)

Key research provider: University of New England

What’s it all about?

This investment was established at the end of 2016 to deliver weed management tools and approaches. The four-year project is identifying and improving integrated management strategies for high-priority weeds, and is developing guidelines and a host of resources for growers. Its work will ultimately help reduce the dependence on herbicides and tillage for weed control, which can become ineffective when used repeatedly.

The project team continues to make progress across the following research areas:

Weed management guides

The project team has published weed management guides for the priority species, pigweed (Portulaca oleracea), marshmallow (Malva parviflora), and blackberry nightshade (Solanum nigrum).  Additional guides are being finalised for amaranth (Amaranthus spp.), wild radish (Raphanus raphanistrum), common sowthistle (Sonchus oleraceus), and chickweed (Stellaria media).

Economic impact of weeds

The economic impact of weeds was assessed for 19 vegetable farms in New South Wales, Victoria, Tasmania and Western Australia. The direct costs of managing weeds and the estimated economic impact on crop yield and quality were included in the evaluation.

In the report, Economics of weed management in the Australian vegetable industry, it was found that the weighted average reduction in operating profit due to weeds was $2,090 per hectare, with the result for organic farms approximately six times higher than in conventional (herbicide-focused) management systems.

Integrated weed management manual

Development of the Integrated Weed Management Manual is continuing, with industry feedback providing valuable insight as content is finalised. 

Pot and field trials

Four cover crop trials in different vegetable growing regions across Australia have been established, to understand the implications of using different winter and summer cover crop types on the weed seed bank, and to demonstrate how cover cropping may be strategically used during fallow or non-crop periods to help improve on-farm weed management. Data collection and analysis is ongoing for the cover crop trials, hand weeding experiment, and cover crop/weed competition experiment.

Extension activities

A case study was prepared and published, Effective Integrated Weed Management: Diligent hand weeding eventually pays off, featuring The Loose Leaf Lettuce Company in Western Australia.

The team also carried out extension field work in Victoria to gather resources for another case study of effective IWM.

Future events include a vegetable industry field day at Gatton in Queensland, and up to three additional case studies of successful IWM.

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The latest information about the project – including articles, reports, case studies and management guides – can always be found on the University of New England’s website.

Read more in this article, Managing important weed species on Australian vegetable farms, published on page 24 of WA Grower, Winter 2019 edition.

The team reports progress in all aspects of their research into weeds including…

Weed seed banks in soil

Soil seed banks form a key source of weed infestation in vegetable crops since weed seeds can survive in soil for decades and give rise to weed plants year after year. To study the size and distribution of weed seed banks in vegetable fields, a survey was carried out across all states and territories of Australia.

Soil samples were collected from 36 vegetable farms to a depth of 20cm. Weed seeds for three depth categories (0-5 cm, 5-10 cm and 10-20 cm) from each farm were counted using the seedling emergence method and identified to species or genus level.

A total of 63 species were recorded in soil seed banks. Species causing the most problem for growers were marshmallow, fat hen, blackberry nightshade, chickweed, milk thistle and dwarf nettle. The preliminary results indicate that weed management strategies in vegetable crops should focus on depleting the seed bank in the top 10 cm.

Data analysis continues, so keep an eye out for further updates from the survey.

Field trials on tillage and irrigation

The team is conducting a series of trials to assess the effects of tillage and irrigation methods on the movement of weed seeds down into the soil. They are testing it on various soil types.

Integrated weeds management manual

The team has begun developing an integrated weeds management manual which will incorporate findings from the team’s research studies as these progress.

Economic analysis of weed management techniques

Field trips and farmer interviews are underway to calculate the costs and benefits of innovative weed management practices in vegetable production, compared to widespread practices.

Results are in for an initial cover crop trial in Myalup WA while others are underway to investigate the economics of cover cropping for weed suppression.

Other field and pot experiments

Hand weeding in Australia and globally has been studied with findings summarised for inclusion in the upcoming manual.

A review of commercially available hand weeding implements for vegetable production systems has also been completed, with the aim of identifying the most relevant implements for further evaluation. A field trial of these implements is planned to test effectiveness and efficiency of implements including a rotary cultivator, long-handled draw hoe and a goose foot hoe. In addition, the physical effects of the various tools on the people using them will be considered.

Another study is looking into the effect of plant age and other agronomic factors on the control and recovery of pigweed (Portulaca oleracea).

A number of graduate students are taking part in the studies to build capacity in the area of weeds in vegetable production, providing long term benefit for research in the industry. One project looked at the effect of mulch types in controlling nutsedge, finding that those that let no light through were much more effective than transparent or semi-transparent films. 

Another student project evaluated whether vinegar, eucalyptus oil and salt have the potential to control weed seed germination and growth. Although the herbicidal effect was not as strong as glyphosate, vinegar and eucalyptus oil showed moderate control of weeds at early growth stages.

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