- Bar clearance and tyne layout have a strong influence on a machine’s ability to cope with heavy stubble loads.
- Select a seeder based on your farming system, cropping environment and your financial position.
- Stubble management starts at harvest. Stubble height and residue spread at harvest will directly impact sowing.
A common reason given by farmers who remove stubble is that it hinders sowing operations and subsequent crop emergence, mainly due to seeder blockages, clumping and poor seed to soil contact. However, despite the challenges of stubble retention, it has been widely adopted by Victorian grain growers because it improves soil structure, prevents wind erosion, reduces evaporation, and improves microbial activity in the soil.
To overcome challenges at sowing, particularly when stubble loads are above 3t/ha, growers have been adjusting their systems to eliminate or minimise problems as they arise and seeding machinery has been adapted and developed to better suit a stubble retained system.
There is now a large and diverse range of seeders available to growers and selecting the best machine for the farming system is not always simple.
As part of the ‘maintaining profitable farming systems with retained stubble in Victoria and Tasmania’ project Birchip Cropping Group (BCG), Southern Farming Systems (SFS), Irrigated Cropping Council (ICC) and the Victorian No-Till Farmers Association (VNTFA) have been investigating machinery and/or adaptations that will improve sowing efficiency and crop productivity in a retained stubble system.
Findings from seeder demonstrations and grower surveys carried out as part of this project, as well as anecdotal evidence from leading farmers and consultants, has been used to develop these guidelines.
Blockages of sowing implements is one of the major impediments to stubble retention, particularly in irrigated and high rainfall zones, where yields and stubble loads are generally high.
Challenges can arise at seeding time when the stubble from the previous crop is too heavy (above 3t/ha of dry matter) or tall, or if chaff and straw hasn’t been chopped and spread evenly at harvest.
Using seeding equipment designed for retained stubble systems will minimise blockages, but does require a significant capital investment.
Alternatively, modification to the profile and tyne layout of the seeder bar can reduce stubble clumping and blockages, and improve the machine’s ability to cope with heavy stubble loads (5-7t/ha).
Seeder set-up and modifications
It is possible for simple modifications to be made to the seeder that will enable it to better cope with stubble.
According to GRDC stubble management factsheet, ‘Strategies to manage winter crop stubbles without reaching for the matches’ (2011), seeder modifications that will enable sowing into stubble include:
- A straight rather than a curved shank will avoid residue building up.
- Shanks with a rounded cross section have improved residue flow, compared to square shanks.
- Vertical or slightly backward leaning shanks promote a constant off-balancing effect on residue, reducing build up.
- Sudden changes of shape in shank profile inhibits residue flow and promotes clumping. High ‘C’ shapes, where the upper part of the ‘C’ is above the stubble flow work well.
- ‘Stream-lined’ designs with recessed bolt heads for point mounts also reduce residue catching.
- Existing curved shank tynes can be improved by retrofitting stubble tubes to make the face of the shank round and more vertical.
- Long knife-point openers can increase the effective vertical clearance of short tynes, but their break out rating needs to sustain the greater lever arm effect.
- Tyne shank add-ons (Pig Tails or other plastic/metal guards) improve trash flow around the tyne.
- Tread wheel residue manager’s hold down the stubble beside the shank as it moves through.
- Row cleaners move stubble away from the disc to prevent hair pinning and assist in crop establishment.
- Residue pinning wheels (Morris Never-Pin wheels) hold the stubble on either side of the disc to assist in cutting ability.
Component racking is one aspect of the seeder that will also impact stubble retention. Both disc and tyne seeders are best suited to ‘up and back’ seeding. Disc planters do not cope well with going over contours or on hill sides, but are perfectly suited to CTF (disc seeders can easily inter-row sow which is a perfect complement to stubble handling ability).
Selecting a seeder
As part of the GRDC stubble initiative, Southern Farming Systems (SFS) has conducted extensive work on seeding system performance in relation to stubble retention.
This work has included:
- A seeder demonstration which compared 15 different seeders and the performance of crops sown by them (Table 1);
- A field trial which specifically compared disc and tyne seeders;
- Stubble management comparisons which examined seeder performance and canola establishment under different stubble management regimes; and
- A stubble management for disc seeders trial at Streatham.
Table 1. SFS 2015 seeder demo dry matter results (t/ha) for each strip as at November 19, 2015.
|Make||Width (m)||GS65 DM (t/ha)||Yield (t/ha)|
|Serafin Ultisow disc demo||2||7.8||1.42|
|John Deere 1890 + liquid||9||7.87||1.76|
|Vaderstad Rapid disc||3||8.41||1.15|
|John Deere 735 (19cm)||12||9.03||1.68|
|John Deere disc 1890
|Great Plains Precision planter||3||6.46||1.3|
|Amazone Cirrus 60032||6||8.98||1.46|
|Equalizer – South African seeder||12||9.52||1.56|
Key learnings from this work thus far are:
- Real time kinematic (RTK) guidance is a critical component to inter-row sowing
- Each seeder has varying capacity to handle retained stubble
- As a rule, discs handle higher loads than tyne and press wheel machines
- Wider tyne spacing across and along the bar will improve stubble handling
- Changing the angle of sowing direction slightly can minimise blockages
- Guidance auto steer on seeder bars will improve inter-row sowing
- Tynes and discs have varying degrees of soil throw and crop safety for pre-emergent herbicides
- Isolation of fertiliser from seed will limit seed burn.
Disc versus tyne
The uptake of retained stubble farming practices has created an increasing interest in disc seeders, predominantly because of their improved residue handling capacity and inter-row sowing capabilities.
Results from an initial survey conducted for the stubble initiative highlighted that 15 per cent of survey respondents (growers and industry representatives from Wimmera and Mallee) own a disc planter with John Deere being the most popular seeding implement. The main reasons for purchasing a disc planter was for less soil disturbance, improved seed placement and germination, better stubble management (residue flow assistance) and versatility in many soil conditions.
However, disc seeders have traits that require unique agronomic management to maintain crop yields at profitability levels the same as traditional systems. Namely, lack of soil throw in a disc system means the effectiveness of commonly used pre-emergent herbicides that work by incorporation (IBS) will be impaired.
Another challenge of disc seeders is ‘hair-pinning’ which results in poor contact between the seed and soil, and poor germination and emergence. Most of the disc seeders available rely on the weight of the machine for soil penetration although, newer models are set on a sharper angle which allows the disc to slice through soil and cut stubble rather than rely on the machine weight (Farmlink, 2013).
In a stubble retained system, there are pros and cons for both disc (Table 1) and tyne seeding systems, but it should be remembered that differences in capabilities will vary according to the environment they are being used in. That said, design is a very important consideration when evaluating seeders for your specific situation.
Table 1. Benefits and limitations of disc seeders.
|Ability to handle large stubble loads of various crops.||Poor handling of sticky soils which puts added pressure on bearings.|
|Good soil cover and less soil throw.||Hair-pinning can occur when stubble load is high.|
|Improvements to soil structure: health and quality, erosion control (assisted by retained stubble).||Cannot rely on mechanical herbicide incorporation resulting in possible herbicide crop damage.|
|Faster seeding and a range of cost savings (fuel, power, seed labour).||Damage and wear and tear on stony ground.|
|Improved reliability of crop establishment.||Low crop vigour and slow root development|
|High degree of accuracy when inter-row sowing.||Uneven furrow closure|
|Increased seed placement accuracy.||Poor disc drive when operating in loose sandy soils and sticky clays.|
|Improved water infiltration and preservation which will lead to greater crop growth later in the season where moisture is required most (achieved by less soil disturbance).|
Proponents of disc systems would argue that the above limitations can be overcome if the user is prepared to embrace it as part of the whole no-till system and adopt necessary practice changes (such as alternatives to pre-emergent herbicides IBS to control weeds).
These key messages were reiterated by Western District farmers Troy and Grant Keating who said that while transitioning to a disc/no-till system takes time, and there are challenges along the way, they were committed to persisting because they believed the long-term benefits were there (2015, Vic No Till Famer’s Association magazine).
Results from the SFS disc versus tyne demonstration revealed no significant differences in wheat yield (p>0.05) between disc (Figure 1) and tyne (Figure 2) systems, however there was a small cost saving for the disc system from faster sowing speeds, higher harvest efficiency and reduced fuel costs (Table 3).
Table 3. Cost calculations for sowing efficiency, harvest efficiency, fuel use and yield SFS disc versus tyne trial 2015.
|Yield||Harvest time||Fuel use||
|Advantage disc v tyne||
|0.55 t/ha†||1.81 ha/hr§||2.11 L/ha**|
|Value of differences ($/ha)||2.10||135.85||13.23||2.53||
* Contract sowing @ $45/ha. 12m disc takes 35hr less time over 1000ha at 12km/hr versus 12m tyne at 8km/hr.
† Red wheat valued at $247/t. Value of difference between disc and tyne treatments mean yields.
§ 1.98 extra minutes per ha valued at $6.66/min ($400/hr contract rate).
** 2.11 L/ha less diesel valued at $1.20/L. Financial estimates of cost not yet available.
Tips for transitioning from tyne to disc
Leading the charge in the adoption of disc seeding systems are the members of the Victorian No-Till Farmers Association. According to the organisation, transitioning from a tyne to a disc system, while worthwhile, is not always simple.
The following tips have been developed to support growers negotiating the transition.
- Have the right mind set – understand that a disc system is going to be different to your tyne system.
- Sell your tyne so you are not tempted to go back to it at the first sign of trouble.
- Sow dry/early to overcome stickiness in clay soils. The more residue you have the less this will be a problem.
- Harvest management is critical. It is essential that extra attention to detail is employed at harvest time. It is imperative that the residues are spread uniformly so your discs are cutting through an even layer of chaff, not through uneven clumps.
- Get your existing tyne machine on the row spacing you intend for your disc beforehand.
- Harvest your cereals on the shorter side before using the disc for the first time to help with residue flow.
- In your first year of using a disc system, sow deep, as your gauge wheel could ride high on the old tyne furrow.
- You may need row cleaners to level the ridges and furrows for your disc and gauge wheel. You could also consider a once-off harrowing or prickle chain to level your paddocks to ease the transition from tyne to disc. Level paddocks are critical for good seed placement.
- If wet, wait until conditions dry a little for your disc sowing. Even if your neighbour is out seeding, be strong and resist the temptation to go out – the wait will be worth it.
- Consult with your agronomist regarding pre-emergent herbicides. Also note that you cannot band urea when using discs.
- Standing stubble is better. Once you have mastered using discs, aim to cut stubble as high as possible (consider a stripper front).
- Contact your local Vic No-Till grower who is experienced in stubble retention systems using discs for advice and trouble-shooting tips.
Farmlink, 2013, ‘An update of stubble management and practices in southern NSW’, Stubble Management. Accessed at: http://www.farmlink.com.au/_literature_146390/Stubble_Management_Practices_and_Research_in_southern_NSW
This research is being conducted by BCG and VNTFAas part of the GRDC Maintaining profitable farming systems with retained stubble initiative (project BWD00024 ‘Maintaining profitable farming systems with retained stubble in Victoria and Tasmania’).