But growers are advised to closely consider soil moisture levels at the required ripping depth and machinery set-up. Weighted rollers, either towed behind the ripper or used after, may be needed to level the surface for seeding success and, ideally, deep ripping is best in a controlled traffic farming (CTF) system to increase the longevity of benefits.
Researchers are warning growers who are considering early deep ripping to assess how wet the subsoil profile is and what crops will be sown on the ripped area.
If paddocks are too wet, there is a risk deep ripping can do more harm than good by causing ‘smearing’ (instead of fracturing) and increasing soil strength along the ripping line. This creates a hostile zone for root growth and negates the benefits of loosening the soil.
Deep ripping can leave paddocks very soft and make seeding implements vulnerable to sinking and sowing too deep.
Combined with the soil re-compaction that occurs within the first pass of a wheel in uncontrolled traffic, a big investment in the soil can then become redundant within 12 months. Research and experience in WA shows the best value comes from a single rip that generates several years of crop yield response.
Prime on-farm considerations for deep ripping early in 2018 that can help to achieve optimal ripping depth, soil breakout and area able to be treated include:
- assessing soil conditions, especially moisture at the desired ripping depth and depth of hardpan;
- traction implications;
- trash flow management; and
- required machinery adjustments to match conditions.
Major risks of getting it wrong are poor crop establishment at seeding if soil is too soft and/or getting higher herbicide phytoxicity (strength of action) - potentially damaging crops. Understanding the impacts of deep ripping and latest WA trial results were outlined at last month’s recent Grains Research and Development Corporation (GRDC) regional Grains Research Update in the Geraldton port zone and in Perth.
BENEFITS OF DEEP RIPPING
Department of Primary Industries and Regional Development (DPIRD) research officers Wayne Parker and Bindi Isbister told the Update events that ripping to 50–70 centimetres is one of the most effective ways to remove deep subsoil compaction on WA’s deep sands, sandy loam duplex and some clay soils.
They said this can help to:
- improve soil biological activity and structure;
- reduce soil strength;
- avoid stunted crop root growth; and
- address waterlogging issues.
Deep ripping has been demonstrated to be particularly effective when used in controlled traffic farming (CTF) systems.
ECONOMICS OF DEEP RIPPING
Trials and economic modelling carried out in 2016-17 with GRDC investments showed crop responses to deep ripping varied with rainfall and temperature in a single season and highlighted the importance of considering returns across several seasons.
DPIRD researchers estimate costs range from $50–60 per hectare for standard ripping (to a depth of 30–40cm) up to $70–90/ha (for ripping to a depth of 50–70cm). This will depend on machinery type and soil conditions.
At a DPIRD-led trial site in Binnu, in the absence of topdressing manure, responses from ripping to a depth of 55cm were sufficient to cover the investment in the first year and remained economic in year two.
At a DPIRD trial in Munglinup, the value of the ripping without topsoil inclusion plates was realised in year two, with topsoil slotting improving the return on investment (ROI) of year one.
A lime investment at this site was predicted to produce a positive ROI before year five, providing more than $100/ha in extra value compared to not topdressing with lime.
ASSESSING THE SOIL FOR DEEP RIPPING
It is vital to understand the soil type and potential constraints before deep ripping – or deciding if another amelioration technique will be more effective to address compaction issues. The key is to achieve optimal soil ‘breakout’ and a good paddock surface finish for successfully sowing the 2018 crop. This will be influenced by: soil moisture, type, strength and structure; tine spacing and length; point size and shape; and ripping depth.
Wayne and Bindi’s tips for checking soil prior to deep ripping include:
- rolling a handful of subsoil into a three millimetre diameter-thin sausage to test cohesion (if it maintains its shape, it is too wet to rip);
- ripping a strip of a paddock and digging a hole behind the furrow to examine the ‘breakout’ profile;
- checking for the required shape of a ‘V’ from the bottom of the ripping tine; and
- looking for a ‘Y’ shape, which means the soil is shattering from further up the tine (not the point).
Wayne said a Y’ shape is not preferred and risks an unbroken hard pan on the sides of the tine. This damages the soil profile and makes it harder for crop roots to explore the soil at that depth.
More information about assessing conditions for deep ripping and seeding into these areas can be found on the DPIRD website at: www.agric.wa.gov.au/n/105.
SETTING UP MACHINERY
Deeper ripping is a slow operation and it can be tempting to choose a wide ripper, according to Bindi.
But she said narrow widths of six metres or less are typically required to rip deep below 50cm due to tractor capacity to get power to the ground.
She also suggested selecting a ripper width to fit in with multiples of the machinery matching ratio for CTF systems.
“All rippers can rip, but the key to choosing the right one will depend on your soil type, depth of the hard pan and other constraints present,” she said.
“For example, if you have already spaded and there is a hard pan still at 20 – 40cm – then a deeper ripper is needed.
“If water repellence is an issue, consider an implement that mixes and rips at the same time.”
A demonstration with GRDC investment in 2017 investigated eight deep ripping machines/configurations. All were found to increase crop yield compared to unripped conditions. This project was carried out in conjunction with the Mullewa Dryland Farmers’ Initiative on an Eradu yellow sand on Tammar Plains.
Ripping at this site, irrespective of machine type, increased yields by more than 8 per cent compared to unripped areas. More information and further trial results from this project are available from Wayne Parker at: firstname.lastname@example.org
He said when ripping, considering the ‘wear and tear’ on equipment is important but often overlooked.
“Doubling the load on a bearing reduces its life by a factor of 10,” he said.
“For example, if machinery is able to pull an airseeder at 8km/h, but the deep ripper at only 4km/h, the required drawbar force has doubled and reduced the life of the bearings in the drive train (by a factor of 10).”
Tine width and type
Wayne said a typical rule-of-thumb for tine row spacing is to use double the width of seeding tine spacing, which allows each plant row access to the ripping slot. Common row spacings for deep ripping are 48cm, 50cm or 60cm.
He said research under WA conditions indicates wider-spaced tines leave larger unbroken, high strength, soil ridges in the profile, effectively shattering less soil than narrower tines.
“This can be beneficial, as less tines means less horsepower and more area can be ripped,” he said.
However, a 2016 DPIRD trial on yellow sand at Binnu found the yield response from 100cm tine spacing must be at least 60 per cent of the yield response from 50cm tine spacing to get a ROI from ripping in one season.
‘C’-shaped tines can bring to the surface subsoil that often has a higher clay or nutritional (especially potassium) content. In comparison, a straight leg tine can achieve a greater ripping depth. If ripping rocky soils, hydraulic breakout is preferable to shear bolt breakout, according to Wayne.
“Some tines can be fitted with wings or different sized points that can increase the shatter effect achieved during ripping, but adding attachments increases draft on the ripper making it harder to pull,” he said.
“A shallow leading tine configuration (a deeper working tine in line behind a shallow tine) or ripping in two ‘bites’ can reduce the horsepower requirement and achieve more even break out (less large clods).
“A shallow leading tine has been found to be more effective when ripping in dry conditions. If in a CTF system, the ability of the ripper to lift or remove/replace a tine quickly in the main wheel-tracks is important. Ideally, wheel tracks should not be ripped in order to maintain the benefit of firm tracks reducing fuel use and achieving better ‘traffic-ability’ in wet conditions.”
Rollers and packers
Towing a weighted roller behind the ripper, or using one after ripping, has been found to help to firm the seed bed and crush large clods often produced when ripping heavier soil types. This optimises the finish of the paddock surface and enables sowing depth control and good establishment around seeding. Bindi said there are commercially available rollers, but some growers have designed simple alternatives. These include an angle iron welded to large diameter steel pipe (filled with water to add weight) or truck tyre rollers.
She said coil packers can help level the paddock after ripping, but if ripping deeper than 30cm, or in moist conditions, a heavier weighted roller is likely to be required.
Rollers will affect the amount of standing stubble remaining, so she advises close assessment of erosion risks before ripping – particularly in very sandy soils. In these soils, deeper ripping and topsoil slotting may be beneficial to maintain cover compared to stubble burial from mouldboard ploughing or spading. If stubble cover is below 50 per cent in autumn, then ripping may increase risk.
This can move topsoil and other soil amendments down the soil profile into the subsoil while deep ripping. Typically, topsoil inclusion plates are bolted behind the deep ripping tine at a suitable depth to run at the base of the topsoil (about 100–150mm below the soil surface). The plates hold the slot open to allow the topsoil to fall in behind the tine.
SEEDING AFTER DEEP RIPPING
Bindi said recent experience and trials – especially in WA’s higher rainfall zones – indicate that after deeper ripping, soil is very soft and can lead to seeding equipment getting bogged or sprayers falling off un-ripped tramlines.
The best way to manage this is yet to be fully analysed. But she said growers have found some useful strategies, including:
- lifting more tines behind the tracks to leave a wider tramline;
- running shallow working tines behind the wheel track; and
- changing press wheels to those with more flotation.
For more information about seeding after deep ripping click HERE.
IMPORTANCE OF CTF WHEN DEEP RIPPING
Research in WA has shown CTF is an integral part of any deep ripping system to minimise re-compaction and increase the longevity of its benefits.
Experience and on-farm observations have shown that, on some deep sands, the benefits of deep ripping can persist for at least ten years on a fully matched CTF farm.
TRIALS FOR 2018
GRDC is investing in further deep ripping research across the WA grainbelt this year, including four new trials in the Kwinana East and Esperance port zones.
These trials at Wyalkatchem, Salmon Gums and Grass Patch will investigate ripping in soils other than responsive deep sands.
This research will complement existing WA trials supported by the GRDC ‘Minimising the impact of soil compaction on crop yield’ project.
GRDC Project Codes: DAW00243, DAW00244
08 9956 8532
Wayne Parker, DPIRD
0429 080 074, 08 99568511