More than any other country, Australia has persistently focused on the idea of collecting weed seed at harvest and keeping them from making it into the soil’s seed bank.
The developmental process in Australia has taken several forms – some relatively simple and cheap and others that require extra machinery. But all show some degree of success when it comes to keeping new weed seed out of the soil.
Thanks to a series of educational videos, U.S. farmers can now gain an overview of the various techniques and technologies that Australian agriculture has been putting into place.
The videos were produced by WeedSmart, an industry-led initiative that focuses on weed management, particularly in dealing with resistant weeds in the country.
The umbrella term for all this is harvest weed seed control (HWSC, for short).
The HWSC courses – available on YouTube – include 8 segments, with 6 videos providing overviews of these systems. Here’s a quick summary of the available videos.
Quick points before you delve into the videos:
- None of the systems are promoted as a replacement for effective herbicide programs. Rather, they focus on reducing seed populations and weed pressure.
- Videos in the series outline advantages and disadvantages of each system and also give general economic estimates on costs and trade offs in terms of nutrient removal.
- Terminology is a bit different, of course. The term paddock means a field and Australians refer to combines as harvesters.
The first two videos include:
Michael Walsh, a University of Sydney weed scientist, gives an overview of the various HWSC methods. He also reviews research findings relating to weed seed population trends when HWSC is put into place. Walsh has been working with HWSC concepts for 20 years.
Several HWSC approaches involve removing all or part of the crop residue or burning the residue. That raises questions about how much of the residue’s nutrient load is lost. This module looks at the dollars-and-cents tradeoffs caused by residue removal or burning. Those numbers, of course, are in Australian dollars, so search on line for a handy currency conversion calculator if you want to get into the finer points of the calculations.
The nutrient video and the remaining programs in the series are presented by Peter Newman with the Australian Herbicide Resistance Initiative (AHRI). AHRI is a research and educational program and is funded by grower and governmental entities.
Here are the 6 systems highlighted in the series:
#1. Narrow Windrow Burning
This has become a fairly popular form of seed control in parts of Australia and it’s a cheap system to adopt. Farmers fabricate chutes and attach them to the discharge point on the rear of the combine.
The chute piles up straw, chaff and weed seeds in a windrow, which is easy enough to burn in the right conditions. This video provides information on how the chutes are designed and tips on proper burning.
#2. Chaff Carts
Essentially, the combine tows a single-axel cart. A conveyor system moves the chaff and weed seed into the cart’s holding compartment. The cart dumps the contents from the rear, usually as the combine moves through the field.
Chaff carts were used in the past but then fell out of favor. With early carts, the chaff was blown into the cart, which packed the material too densely for easy burning later. But with the adoption of the conveyor system, the chaff is looser and burns more readily.
The chaff cart is dumped as the combine moves through the field. Later, the pile of chaff and seeds can be burned or even grazed by livestock. In the case of Australia, that means sheep. Slight combine modifications may be needed to more completely separate chaff and seeds from the straw.
#3. Bale-Direct System
With this approach, the combine tows a baler and all the residue blows into the baler. This is a niche option because a grower would need a ready market for straw bales. It remove 95% of the weed seed but also drains away plenty of nutrients locked in the residue. The upfront costs are substantial, as well.
#4. The Harrigton Seed Destructor (HSD)
Researchers in at least 2 U.S. states – Arkansas and Illinois – have been experimenting with this concept. Designed by an Australian farmer, the Destructor is a cage mill that takes in chaff and weed seeds, pulverizes the residue and then drops it behind the combine.
Initially, these were pull-behind units, but the most recent generation of HSDs are integrated into the rear of the combine. It’s a pricey add-on, to be sure. But research shows that it chews up a substantial amount of seeds. Also, all of the residue remains in the field.
#5. Chaff Tramline
This is an option for growers with a controlled traffic system. A deck with a conveyor belt on the rear of the combine deposits the chaff and seed in the tram line, concentrating the weed seeds in a narrower area where the wheels run.
In wet environments, the weed seed in the chaff tend to germinate but never make soil contact or otherwise rot ahead of the next crop year. Or if anything does emerge, future equipment traffic will run it over. Some farmers put sheep in fields between crops to consume chaff and seeds.
#6. Chaff Lining
A relatively new concept, chaff lining is a variation on the chaff tramline approach (above). Instead of depositing the chaff in wheel tracks, it’s funneled from the rear of the combine between the wheels. Compared to tramlining, there’s no chance that machinery will press seeds into the soil later where they might germinate.
Seed dispersed in the chaff would be prone to rotting or some degree of composting. Any seeds that do germinate would have to compete with other emerging weeds. Like chaff tramlining, this is an option for farmers in controlled traffic production. Of all the systems covered here, it’s also the newest approach, so less research has been conducted with the approach.