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Harvest weed seed control with Dr Michael Walsh

Weeds that ‘escape’ herbicide control can quickly contribute vast quantities of seed to a paddock’s soil seedbank.

Research Associate Professor, Dr Michael Walsh, says there are four options for weed seed control at harvest, and all growers should seriously consider implementing one of these strategies every harvest.

These harvest weed seed control strategies are known to work, and if regularly applied play an important role in keeping cropping land productive and, importantly, will extend the useful life of the herbicides currently available.


Narrow windrow burning is fairly cheap. Is it an option for all crops?

Short answer: No.

Longer answer: Narrow windrow burning is best suited to non-cereal crops such as lupins, canola and field peas and cereal crops yielding less than 3 t/ha. In large cereal crops windrow burning poses a serious fire risk. Narrow windrow burning is the easiest harvest weed seed control strategy to implement and is a great place to start for many growers. Weather conditions strongly influence the efficacy of burning and  must be monitored carefully before and during windrow burning.

Is the ‘bale direct’ system an economic option?

Short answer: Yes, if you have access to a suitable market for the bales.

Longer answer: A square baler attached to the harvester collects and bales both the chaff and straw component. There is an obvious risk that weed seed can be relocated, so it is essential that the bales are only used in suitable environments such as a feedlot or dairy. Another safe option is to make pellets using the bale material; a process that will destroy the weed seed. It is important to remember that the economics of baling are very market driven. Other possible future markets may be for electricity co-generation and ethanol production.

What is the most economical option for big cereal crops?

Short answer: A chaff cart.

Longer answer: Chaff carts are a relatively inexpensive option for collecting the weed seed bearing chaff while retaining the straw in the field. Using chaff carts avoids some of the fire risks associated with narrow windrow burning of large cereal crops. The chaff heaps can be set up in an area where it is easier to put firebreaks. Incorporating some straw in the chaff heaps with a conveyor-style transfer system will help the heaps burn better.

I want to maintain the maximum amount of crop residue in the paddock, what is my best option for harvest weed seed control?

Short answer: A Harrington Seed Destructor.

Longer answer: The Harrington Seed Destructor (HSD) crushes the chaff, including the weed seeds, and returns all the chaff and straw to the paddock, maximising the nutrient and soil moisture benefits of these residues. The initial capital cost of the HSD is a barrier for many growers but there is potential for harvest contractors to offer growers the use of a HSD as an additional harvest service.

How to ask a WeedSmart question

Ask your questions about the Harrington Seed Destructor, or any other herbicide resistance management strategy, either using this blog, or using Twitter @WeedSmart.

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