Australian Herbicide Resistance Initiative (AHRI)

Chaff carts – good for the crop and the sheep

So often in life, there are things that conflict with one another. Take the Australian cricket team for example. Social media is great for the social lives of the players, but it is disastrous for their batting. You simply can’t bat all day in a test match when you have the attention span of a goldfish!
Farming is just the same. There are conflicting farming practices. Often what is good for the crop is detrimental to the sheep, and vice versa.
Until now.
The humble chaff cart is good for both the crop and the sheep. Ed Riggall is a Western Australian based farm consultant from AgPro Management. Ed specialises in livestock management and was frustrated that there was no data to evaluate the grazing of chaff dumps. Without funding, Ed set up trials at four locations in southwest WA in 2015/16 and got some great results. Essentially, the sheep did very well when grazing chaff dumps, particularly in canola stubble.
But won’t the sheep just spread the weed seeds back over the paddock? Fortunately, the answer to this question is no.
Chaff carts are a great tool for mixed farmers to feed sheep and smash their weed seed bank at the same time.
Sheep grazing on chaff dumps can have several benefits

Sheep grazing on chaff dumps can have several benefits

Almost every grain farming system in Australia is suitable for a chaff cart. Low rainfall, high rainfall, continuous crop, mixed farming, it all works. But it seems now that the greatest fit for the chaff cart is a mixed farming system that includes sheep.

AgPro Management set up trials at four sites in the WA Wheatbelt. Paired paddock trials were set up at each site, directly comparing sheep where a chaff cart was used to sheep where a chaff cart was not used, in otherwise duplicate conditions. The paddocks were analysed for feed quantity and quality prior to the trial and all sheep were weighed and condition scored fortnightly throughout the trial.

Grazing chaff dumps wins at all sites

The graphs that follow show how the sheep grazing chaff dumps did better than the sheep without chaff piles in terms of weight at all four sites. Condition scores are also available from Ed Riggall here, if you would like to look at the data more closely.

Tenterden – Barley

Figure 1

Figure 1

Figure 1: Live weight of sheep grazing barley chaff dumps compared to grazing paddocks without chaff dumps at Tenterden. There was 87mm of rain which fell at the beginning of the trial and a further 24mm of rain fell five weeks into the trial.

Kojonup – Canola


Figure 2

Figure 2: Live weight of sheep grazing canola chaff dumps compared to grazing paddocks without chaff dumps at Kojonup. 18mm of rain fell at the two-week stage of the trial and a further 97mm of rain fell eight weeks into the trial.

Darkan – Oats

Figure 3

Figure 3

Figure 3: Live weight of sheep grazing oat chaff dumps compared to grazing paddocks without chaff dumps at Darkan. 87mm of rain fell at the beginning of the trial.

Cranbrook – Wheat 

Figure 4

Figure 4

Figure 4: Live weight of sheep grazing wheat chaff dumps compared to grazing paddocks without chaff dumps at Cranbrook.

More weight

Results from these trials show that investment in a chaff cart is very much worthwhile, even in a wet summer. The trials were affected by early rains, which reduced the quality of feed in the chaff piles and stopped sheep from feeding. The Cranbrook trial took place later in the season (March/April as opposed to December/January), so the chaff piles had been left exposed to rain for several months post-harvest, which is likely to have affected the quality of feed. All of the sheep on the chaff piles had gained more weight than the sheep without chaff piles at the end of the trial.


Figure 5

Figure 5: Weight advantage of sheep (kg) of sheep that grazed chaff dumps over and above those that did not at the six-week stage of the trial. These trials were also supported by Icon Agriculture who collected the Darkan data and Allflex Tags who provided EID tags .

Chaff dump feed quality analysis

Figure 6

Figure 6

Figure 6: Crude protein (%) and metabolisable energy (MJ/kg DM) feed analysis from chaff dumps.

There is money in grazing chaff dumps

The weight difference observed can be converted into money saved on supplementary feeding to get the sheep without chaff piles up to the same weight as the sheep without chaff piles. Ed used analysis of a typical, model farm (2000ha, 50% crop, 9.5 DSE/ha) and found there would be an average saving of over $29,000/annum and an Internal Rate of Return on Investment in a chaff cart of 36% per annum over 20 years, based on evidence from this season, which was detrimentally wet.

More lambs

The farmers at Kojonup and Cranbrook recorded the individual scanning results for ewes tagged in the trial. The lambing percentage was 25% higher in the ewes that had been on the chaff piles at Kojonup and 8% higher at Cranbrook. This adds another element of real value to the use of chaff carts. This is consistent with the results of previous trials, most recently the Lifetime Wool trial, showing that ewe productivity is higher in heavier sheep with higher condition score.

Figure 7

Figure 7


This is a single year of trial data in a year with a very wet summer which is likely to have had a negative impact on chaff dump grazing. Yet the results of sheep grazing chaff dumps were very encouraging. Hats off to Ed Riggall for undertaking this work without any funding. The chaff cart is one of the few examples of a tool that is good for both the sheep and the crop, and for this reason chaff carts are likely to have a long future in Australian cropping.

P.S.  This article was written before the Adelaide test match!!!

For media enquiries, contact Jessica on 08 6488 3189 or via email at jessica.strauss@uwa.edu.au

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3 Responses to Chaff carts – good for the crop and the sheep

  1. Bruce Nairn November 28, 2016 at 9:46 am #

    Does anyone know what speed to run chaff cart drapers/belts at?

  2. Bungarra November 28, 2016 at 9:23 am #

    Opps – RE Bungarra, I used my Disqus name and not my Facebook name.

    John Holmes, a one time participant in the long game Weeds versus Humans.

  3. Bungarra November 28, 2016 at 9:11 am #

    This work has validated earlier observations in WA and SA re the value
    of using stubble or chaff carts. I would suggest that the comment
    expressing surprise re the good results does not reflect the effect of
    summer rains/higher humidity on the availability of fines too stock. The
    stacks are similar to what Grandpa used to make with hay and the design
    of which reduced water penetration and hence spoilage from rain. I
    would suggest that heaps can supply feed into the start of autumn.

    with the stubble collection systems originally developed in SA, it was
    found that harvesting on very hot days improved the feed value of the
    stubble’s and chaff as there was a higher degree of shattering of the
    systems so that the material digested faster in the animal. Hence a
    larger throughput is possible. The original developments in SA were to
    improve stubble accessibility for stock especially in dry seasons and
    the effect of weed control was noticed later especially as herbicide
    resistance started to become a problem in the early 90’s

    Re the
    decline of in paddock feed, I would suggest that as one gets closer to
    the South Coast in WA the cooler nights with the sea breeze raises the
    humidity and so increases fungal activity and hence degradation of dry
    feed. Personal observations when comparing central wheat belt
    recommendations with results in the Great Southern. Heaps will reduce
    this effect.

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