Sowing into stubble - Why seeder calibration and set up is critical
Date: 28 Mar 2017
- Bar clearance and tyne layout influence a machine’s ability to cope with heavy stubble loads.
- Select a seeder based on your farming system, cropping environment and financial position.
- Stubble management starts at harvest: height and residue spread will impact sowing.
When it comes to optimising winter crop establishment there are vital steps grain growers can take to improve planting outcomes, particularly when sowing into stubble.
Research supported by the Grains Research and Development Corporation (GRDC) as part of the ‘Maintaining Profitable Farming Systems with retained stubble’ project has investigated machinery and adaptations that will improve sowing efficiency and crop productivity.
Conducted by the Birchip Cropping Group (BCG), Southern Farming Systems (SFS), Irrigated Cropping Council (ICC) and the Victorian No-Till Farmers Association (VNTFA) the research produced guidelines for seeder set-up and selection when working in a stubble retained system.
GRDC Grower Services Manager North Sharon O’Keeffe said the guidelines offered growers and their advisors invaluable tactics to select and calibrate seeders when sowing into stubble to maximise crop yield.
“Growers who opt to remove stubble commonly do so because they feel it hinders sowing and subsequent crop emergence, due to issues like seeder blockages, clumping and poor seed to soil contact,” Ms O’Keeffe said.
“Yet, despite the challenges of stubble retention, it is being widely adopted by southern New South Wales growers, because of evidence that it improves soil structure, prevents wind erosion, reduces evaporation, and improves microbial activity in the soil.
“But given the high rainfall last season there is the likelihood many growers will be planting into paddocks with stubble loads above 3t/ha this winter. So it is critical growers adjusting their seeding systems to eliminate or minimise problems when sowing into retained stubble.”
BCG researcher Claire Browne said the importance of seeder set up has increased this year as a result of the heavier stubble loads produced in 2016.
“The key to stubble management starts at harvest time, by taking into account next years planned crop and ensuring all residues are evenly spread across the header width”.
Blockages become an increasing issue when stubble loads are above three tonne per hectare (3t/ha), 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.
This research has also found 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 (ranging from 5-7t/ha).
Utilising inter-row sowing and wider row spacings has also helped growers sow through retained stubbles with greater ease.
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.
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.
Research has also found both disc and tyne seeders are suited to ‘up and back’ seeding. However, disc planters do not cope well with contours or on hill sides, but are perfectly suited to controlled traffic farming (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 trial work on seeding system performance in relation to stubble retention. Key learnings from this work:
- 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
Increasing grower interest in retained stubble farming practices has driven a rise in the use of disc seeders, predominantly because of their improved residue handling capacity and inter-row sowing capabilities.
On farm disc seeders were favoured because of their capacity for less soil disturbance, improved seed placement and germination, better stubble management (residue flow assistance) and versatility in varied soil conditions.
However, disc seeders have traits that require unique agronomic management to maintain crop yields. Primarily the 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, causing poor germination and emergence. Most disc seeders 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.
There are pros and cons for both disc and tyne seeding systems, but design is a critical consideration when evaluating seeders for specific farming environments.
Making the change from tyne to disc
The following tips have been developed to support growers making the transition:
- Sow dry/early to overcome stickiness in clay soils: the more residue the less this will be a problem.
- Harvest management is critical: residues need to be spread uniformly so discs cut through an even layer of chaff.
- Harvest cereals short, before using the disc for the first time to help with residue flow.
- In the first year using a disc system, sow deep, as the gauge wheel could ride high on the old tyne furrow.
- Row cleaners may be needed to level the ridges and furrows for your disc and gauge wheel. Consider a once-off harrowing or prickle chain to level 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 disc sowing.
- Consult 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).
Claire Browne, Research Manager, BCG
03 5492 2787, 0429 922780
Toni Somes, Cox Inall Communications
0427 878 387
GRDC Project Code BWD00024