Methods of weed seed collection at harvest
Narrow header trail
Facilitating narrow header trails (also known as trash windrows) is the cheapest, simplest form of collecting residue. It is done by disconnecting the straw spreaders on the header and allowing the straw, chaff and weed seeds to fall in a narrow trail behind the header. Adding a simple chute forces the residue into an even narrower, more discrete row.
The trail can then be burned during autumn. This has become common practice in many districts when harvesting canola. The high fuel load in the row results in a hot burn and a good weed seed kill. However, any unburned seeds will produce seedlings that will need to be controlled using an alternative tactic.
In a controlled traffic cropping system, straw can be spread while chaff and weed seed are deflected onto the wheel track where they are less likely to grow. During the subsequent growing season spray nozzles can be fitted to another implement to apply a non-selective herbicide to the wheel tracks, killing any germinated weeds. This system fits well where there is a preference for avoiding burning.
Chaff cart
In a chaff cart system the chaff and weed seeds are collected and thrown into a trailing cart. When the cart is full the gate is tripped and the cart self-empties to create a chaff dump.
Harrington seed destructor
Ray Harrington has invented the Harrington Seed Destructor (HSD). Ray first observed a cage mill rendering coal at a Collie coal mine and he decided that this was the type of mill he needed to destroy weed seeds. Testing of the HSD shows that it has the ability to destroy 90-95% of the weed seeds in the chaff it processes. The HSD entered commercial production in 2012 and is now available incorporated into a header (Integrated Harrington Seed Destructor, iHSD)
Other options for weed seed collection at harvest
Baling systems
Baling the chaff is an alternative to grazing. Because the material is already chopped, chaff bales are more attractive to dairy farmers than the conventional straw bales. As proximity to market and price can be limiting factors, this option appeals to those growers who have access to a stock-feed market such as a dairy, beef feedlot or stock-feed mill.