Read time: 4 minutes

Can collecting weed seed make me money at harvest?

with Peter Broley, GRDC Harvester Set-Up Workshops coordinator

WeedSmart is about ‘more crop, less weeds’, which extends to the harvest operation when growers implement any of the available harvest weed seed control (HWSC) tactics.

Peter Broley, GRDC Harvester Set-up Workshops project coordinator, and Primary Sales Australia CEO, says that a harvester set up to minimise grain losses will also maximise weed seed capture.

“We know there are often significant grain losses at the front and out the back of harvesters on Australian farms,” Peter says. “In 2021, a GRDC and GGA project collected grain loss data on 75 sites in Western Australia, revealing that growers were losing two per cent of wheat yield and over four per cent barley yield, sacrificing $29/ha and $58/ha profit, respectively. Losses in canola were over three per cent on average, costing around $68/ha, and as high as 10 per cent in some situations.”

To date, over 1800 growers and harvest contractors have attended the GRDC Harvester Set-up workshops to hone their skills and share their experiences.

“When the harvester is adjusted to minimise grain losses, we find that weed seed capture increases,” he says. “This is a win-win for growers implementing harvest weed seed control. When the weed seed is removed along with the chaff and destroyed through HWSC, it will not impact grain quality at delivery and will not contribute to next year’s weed burden.”

The WeedSmart Big 6 integrated weed management program culminates with HWSC to keep herbicide resistance low, breaking the lifecycle of weeds that have evaded other control tactics in-crop. 

Why do I need to measure harvest losses?

In brief: Visual assessment of grain losses on the ground is very unreliable. A drop tray is an essential tool for measuring losses.

The details: A commercial drop tray system is the easiest way to measure harvester losses. The drop tray attaches under the harvester with a magnet to hold it in place. Place it under the rear axle to measure through-the-machine losses, or behind the side of the front to measure rotor losses.

The drop tray is released, emptied, and the grain weight is measured and added to a mobile phone app to calculate the losses. Several companies make drop tray systems. It is also possible to measure front loss using containers placed in the crop ahead of the harvester.

The aim is to keep grain losses below one per cent for cereals, below two per cent for canola and below 0.5 per cent for pulses.

In the GRDC/GGA trial, growers using drop trays averaged 1.3 per cent machine losses across all crops, while those not using trays averaged 2.9 per cent.

How do I maximise weed seed collection?

In brief: Grow a competitive crop. Ensure maximum grain and weed seed enters the front of the harvester and aim to eliminate rotor losses.

The details: Growing a competitive crop supports harvest weed seed control as fewer weeds are present and those present tend to have weed seed heads held high in the crop canopy.

Pre-shedding of grain and weed seed is typically outside the operator’s control, but they can influence the shattering potential of harvester front impact. To reduce front loss and improve crop and weed seed feed, check that the cutter bar is sharp and the knife sections are straight. Use knife guards to stop shatter loss and look at the angle, speed and depth of the reel. Whatever front is used, ensure it is set up and operated correctly. Select a cutting height that maximises collection of grain and weed seed heads.

Efficient harvesting centres on maximum crop throughput while not overloading the sieves and results in more grain in the bin and more weed seed captured. Essential to this is eliminating rotor losses so that all the weed seed collected enters the chaff stream. The best harvester settings to achieve this vary for each crop, the environmental conditions and the different coloured harvesters. It is crucial to make one adjustment at a time to the harvester settings and use drop trays to measure the effect of each adjustment.

Experienced growers record the harvester settings they have identified for future reference, such as their morning, heat-of-the-day and early-evening settings for each crop.

Does HWSC pay off in the long run?

In brief: HWSC tactics destroy over 90 per cent of the weed seed collected through the harvester. Act now to implement the WeedSmart Big 6, including HWSC, even if herbicide resistance is not yet evident in your cropping paddocks.

The details: It takes time to see the full effect of HWSC, particularly if it is not implemented until after herbicide resistance has caused an explosion in weed numbers.

All harvest weed seed control methods provide similar levels of weed control – collecting, concentrating or destroying over 90 per cent of the weed seed that enters the front of a well set-up harvester. Australian farmers are spoiled for choice when it comes to the options for collecting and destroying weed seed at harvest and keeping downward pressure on herbicide resistance.

WeedSmart western extension agronomist Peter Newman has built a running costs calculator to compare the six HWSC options in different crops. The HWSC Calculator tool allows growers and agronomists to test different scenarios using their own figures to estimate the costs and benefits of the different systems available.

More resources 

GRDC – How profitable is your harvester set-up

AHRI Insight – Harvester set-up to catch weed seeds and grain/

GRDC – Research finds opportunity to reclaim $300m in grain lost at harvest

Agriculture WA – Calculating harvesting losses

Calculating the cost of HWSC for your farm

 

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