To reduce the levels of weed populations, weed seeds are destroyed at or after grain harvest, according to the journal Weed Technology that discusses the harvest weed seed control system.

Combined with herbicide use, this system may further lower weed populations. The effects of this system were observed in 25 large commercial crop fields in western Australia over 10 consecutive growing seasons.

An attribute of most weed species is that the seeds are attached to upright plants, allowing those seeds to be collected during harvest. Up to 80 percent of annual ryegrass seed production is collected during a commercial grain harvest. However, these seeds are typically cast aside as chaff and redistributed over the field.

Four methods have been established to capture and destroy weed seeds at crop harvest. One method involves the use of chaff carts, pulled behind a grain harvester, to collect the weed seed and other discarded plant material. These materials are then either burned or used as livestock feed.

Another method uses a chute to disperse the seed from the harvester into narrow windrows, which are subsequently burned. A baler attached to the harvester offers another method of disposal, creating bales of chaff and straw residue for livestock feed.

Finally, a mechanical device (Harrington Seed Destructor) uses a cage mill to process crop chaff. This device could destroy 95 percent of the weed seed contained in the chaff.

The authors emphasize an integrated approach, as opposed to a stand-alone technique, in order to successfully utilize the system in agriculture throughout the world. In this study, the only 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.  

One of the potential advantages offered by this system 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. 

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 failing to control mature weeds that have gone to seed.  

As weeds continue to become resistant to multiple herbicides, new weed control strategies are needed to ensure optimal crop harvests.  FG

—From Weed Technology news release