How do I set up my harvester to manage stubble
Stubble management begins at harvest.
Harvester setup determines the way stubbles are left after harvest. When planning harvest logistics consider the preferred type of stubble and how crop residues will be managed to ensure successful sowing and crop emergence in the following season.
Stubble residue management depends the type of harvest machinery used, the stubble load and the cropping environment. Stubble following harvest can then be monitored and managed during the summer fallow period to address any issues that may impact on sowing or crop establishment.
Should I harvest low or high?
Cutting height will vary according to crop type and yield, the crop planned for the following season, harvest logistics and the capabilities of the seeding equipment.
Cutting crops low can reduce the need for post-harvest stubble management to improve sowing efficiency the following season. It also maximises weed seed capture when using harvest weed seed control methods such as the Integrated Harrington Seed Destructor (iHSD) and chaff carts.
However, cutting low is slower, potentially putting ripe crops at greater risk from inclement weather. It can also increase the volume of straw and chaff between the rows, which can hinder emergence and yield particularly of smaller-seeded crops such as canola.
Cutting low is suitable:
- If using a tyne seeder
- When there is time at harvest and no other post-harvest treatments are planned
- To maximise biological breakdown of residues
- If herbicide resistant weeds are a problem
Residue needs to spread evenly across the swathe rather than concentrated in a header trail where it increases nutrient tie-up and impedes crop establishment in the following crops. This will ensure sowing efficiency is maintained and emergence is less affected.
If the priority is to cut crops high and harvest fast, stubble may need to be managed post-harvest, depending on the capabilities of the seeder. This may involve performing a second pass during the fallow phase, grazing or baling straw. Read more about How can I reduce high stubble loads after harvest?
Cutting high is suitable:
- If using a disc seeder
- When there is not enough time at harvest to cut low
- If the stubble is to be left standing for inter-row sowing the next crop using a disc-seeder
- If the stubble will be grazed, mulched or burnt prior to next crop
How does harvest height affect efficiency?
Harvesting at lower crop heights places additional demands on machinery and slows down the harvesting operation. Southern Farming Systems (SFS) compared the relative time and cost of harvesting at different heights in a trial at Streatham in 2014 (Table 1). The difference in trash quantity can be seen in the images in Figure 1.
Table 1. Harvest of Bolac wheat is less efficient at lower heights at Streatham using a CASE IH 9120 (2014). Harvest is costed at $400/hr. *Estimated, not recorded. Source: SFS Harvest stubble and weed seed management in wheat and barley – Streatham and Inverleigh (PDF 1.2Mb).
|Stubble height||Time to harvest 100ha (hours)||Harvest cost ($)||Fuel ($)||Cost ($/100ha)||Cost ($/ha)||Saving ($/ha)|
Figure 1. The trash quantity produced when harvesting at 15cm (top) and 30cm (bottom) using a CASE IH 9120. Source: SFS Harvest stubble and weed seed management in wheat and barley – Streatham and Inverleigh (PDF 1.2Mb).
Stripper fronts are now a popular method of harvesting high and are ideal for growers who are comfortable with inter-row seeding or post-harvest residue management such as straw baling or grazing.
The advantages of stripper fronts include reduced fuel use, faster operating speeds and less labour and rotor hours (Table 2). However, they can be prone to higher grain losses and as they leave a higher stubble load, growers may need post-harvest weed and residue management and higher water rates when spraying.
Table 2. The cost of harvesting Suntop wheat in 2014 with a stripper front at 60cm and a knife front at 15cm. Values are means of three replicates taken from John Deere 9770 STS yield monitor and all differences are significant (P<0.05). Source: Farmlink / CSIRO via Farmlink Contractors and stubble (PDF 836kb).
Tall (60cm, stripper front)
Short (15cm, knife front)
Change when harvesting short
As part of the Stubble Initiative, Birchip Cropping Group (BCG) developed a Machinery economics calculator to compare the financial returns for adoption of a stripper front with a traditional draper front (Figure 2).
Figure 2. Growers can use the Machinery economics calculator to compare different harvest machinery options. Source: BCG Machinery economics calculator
What are my stubble treatment options at harvest?
Stubble treatments at harvest may be simply aimed at improving the ease of seeding. However, growers often use this as an opportunity to reduce the weed seed bank. This requires a low cutting height to ensure the weed seeds are collected by the harvester.
Narrow windrow burning
During grain harvest crop residues are placed in a narrow windrow and later burnt. The fire must burn hot enough and long enough to successfully sterilise the weed seeds during the burning process. The temperature needs to exceed 400°C for 10 seconds to kill ryegrass and 500°C to kill wild radish.
Spreading the straw and chaff the width of the swathe
Residue is spread evenly across the comb swathe where the consistent and relatively small particle of the stubble will break down more quickly to make sowing easier in the following year. It has little or no effect on weed management.
Chaff decks or chaff tramlining
Chaff decks place chaff (and weed seeds) on the wheel tracks in controlled traffic situations. The straw is distributed evenly behind the harvester or onto the wheel tracks in controlled traffic.
While the effect of this system on herbicide-resistant weeds has not yet been rigorously evaluated, grower experience indicates it is an effective way to manage stubble and reduce the weed seedbank.
Chaff cart systems have been found to collect 30 to 85 per cent of annual ryegrass seed and 85 to 95 per cent of wild radish seed entering the harvester.
Integrated Harrington Seed Destructor
To manage herbicide-resistant weeds the Integrated Harrington Seed Destructor (iHSD) and other weed seed impact mills provide an alternative solution to narrow windrow burning. The iHSD is a machine that grinds the chaff and weed seeds coming through the harvester. This enables one pass weed seed processing to eliminate all weed seeds that are picked up with the crop.
Farming Systems Groups
- BCG Stubble management at harvest
- CWFS Harvest management in retained stubble systems in Central West NSW (PDF 684kb)
- Farmlink Contractors and stubble (PDF 836kb)
- FarmLink What sort of stubble – It all begins at harvest (PDF 578kb) and resources (PDF 447kb)
- Riverine Plains Managing stubble at harvest improves sowing success (PDF 1.1Mb)
- Riverine Plains Successful sowing into stubble calls for adequate preparation (PDF 610kb)
- UNFS Managing stubble at harvest (PDF 1.1Mb)
- BCG Machinery economics calculator to help growers considering purchasing a stripper front
- GroundCoverTM Supplement (2018) Profitable header setup
- GroundCoverTM Supplement (2018) South Australian growers reap the benefits of HWSC
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