Mechanical Weeding the Answer to Resistance Issues?

A long-term study in Australia is testing mechanical weed-control methods in combination with herbicide use to target weed seeds during harvest, reducing the quantity of weeds that can grow in future crop cycles.

One advantage offered by this combination is that removing most of the weed seed will lessen its ability to develop resistance to the herbicides. Resistance to herbicides among weed species has become widespread and is negatively affecting agriculture, particularly in Australia.

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Ryegrass and wild radish that have developed resistance to multiple herbicides now dominate fields in Australian crop production. The current principal practice of weed control relies primarily on herbicides to manage weeds, but fails to control mature weeds that have gone to seed.

According to the journal Weed Technology, the study has established four methods to capture and destroy weed seeds at crop harvest:

1) Chaff carts, pulled behind a grain harvester, collect the weed seed and other discarded plant material. These materials are then either burned or used as livestock feed.

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2) A chute disperses the seed from the harvester into narrow windrows, which are subsequently burned.

3) A baler attached to the harvester creates bales of chaff and straw residue for livestock feed.

4) A mechanical device (Harrington Seed Destructor) uses a cage mill to process crop chaff. According to the report, the device could destroy 95% of the weed seed contained in the chaff.

The effects of this system were observed in 25 large commercial crop fields in western Australia over 10 consecutive growing seasons. The fields that reached the targeted goal of low weed density were those that employed the weed seed harvest system in conjunction with early-season herbicides. The authors recommend an integrated approach, as opposed to a stand-alone technique.

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