"Subsurface compaction is a widespread constraint in WA cropping areas. Estimates suggest that 14 million of 18.8 million hectares of agricultural land have a moderate to high risk of subsoil compaction.” (DAGF, 2015) Farmers in Western Australia are now turning to deep ripping methods to not only help resolve the issues of soil compaction but finding strategies that improve productivity outcomes
With the increasing use of heavier machinery, subsoil compaction in WA has as a result moved deeper by up to 400-600mm down in to the soil profile. “Soils in WA have <35% clay and have little capacity to naturally swell and crack to remove compaction” (B. Isbister, 2016). Sandy soils need depth to compensate for low water holding capacity. Therefore "cropping soils with sandy textures at least 500mm deep, need deep ripping to 550mm or more to decompact hardpans" (DAFG, 2016) and allows plant root access to reach deeper into the soil to access vital moisture and nutrients.
Research done by the Department of Agriculture and Food have shown improved productivity by removing soil compaction by deep ripping to 550mm and topsoil slotting by removing soil compaction in sandy soils “In 2015 trials, The researchers found that new methods of removing compaction in sandy textured soils by deep ripping to 55cm and topsoil slotting could boost wheat yields by 1-1.7 tonnes per hectare and provide a return of $6-$16 for every $1 invested” (N, Lee, 2016).
To optimise the effectiveness of deep ripping to 50 to 60cm and implementing CTF, DAFWA recommends:
- Identifying the soil type and location of the hardpan
- Addressing any associated shallow subsoil constraints to a depth of 30cm (non-wetting soil, soil acidity, sodicity). Consider deep ripping up to 400mm one season then up to 600mm next season with lime if needed.
- Analyse the best deep ripping method for your soil conditions
- Implementing CTF in line with farm machinery replacement schedule.
Convert to CTF widths
Nearly 70% of the compaction caused by wheel traffic occurs on the first pass. This is the basis for adoption of controlled traffic farming and is the "best way to minimise re-compaction and maximize the longevity of soil renovation treatments" (B, Isbister, 2016)
“Using CTF with deeper ripping systems helps to manage the very soft soil conditions after ripping by leaving firm tramlines for better seed depth control, which can improve crop establishment and reduce erosion risks.” (Lee, N. 2016)
"Previous DAFWA trials in the central grainbelt have found crop yields can increase by 0.5-1t/ha where CTF is used in conjunction with deep ripping on compacted sands and the benefits are highest when growing season rainfall is below average." (Lee, N. 2016)
The basic principle of CTF is to match as many wheels tracks as possible so that machines run on firm compact tracks and crop is able to grow happily in un-compact zones. When deciding on the working width, begin with your header as this is the heaviest machine in the system and has the widest wheel base at three metres. "3m wheel tracks is around the ideal spacing as this will incorporate the header" (Isbister, 2013). It is important to keep in mind when selecting an operating width that forty feet is not 12 metres, but 12.2m “small difference, but enough to make it hard to match Australian and imported machinery”
Steps to develop a machinery investment plan
1. Decide on imperial or metric measurement
2. Select an operating width & match in multiples
3. Match the tracks
4. Choose the type of wheel track you want to leave?
Top Soil Slotting
"Trials in the Western Australian wheatbelt have found deep ripping combined with topsoil slotting can increase yields from sandy soils by more than deeper ripping alone." (DAGF, 2016)
Top soil slotting, with soil inclusion plates attached to the rear of deep ripper tines, could deliver increased yield from deep sandy soils" (DAGF, 2016). Inclusion plates open ‘slots’ below the surface of the soil behind deep ripping tines to help direct the loosened topsoil into the furrow. With the use of a flexi-roller, the roller will help push the material in to the slots and firm the surface after ripping to create a more level seed bed. "First year returns on investment for trials with dry growing seasons in 2015 ranged from $6 to $16 per dollar invested" (DAFG, 2016). In addition, top soil slotting helped reduce grain losses from dry and hot spring weather.
Other soil constraints such as soil acidity, sodicity and non-wetting soils can be alleviated using topsoil slotting. Applying soil ameliorants such as organic matter, lime and gypsum at time of top soil slotting. This has been shown to "have more effect on sandy or clay textured subsoils and offer better retun on investment" (DAGF, 2016).
Top- soil slotting is best utilised at low speed of about 4km/h and with a moist subsoil and dry topsoil. It is important to set the plates below the topsoil and to monitor the plates for soil adhesion and stubble blockages.
Inclusion plates are available as an option for our AP51, AP71, AP81 and AP91 Agrowplows
Trailing leading tine design
Studied and proven in sandy soils ‘Deep ripping to 500mm with the help of shallow leading tines gave about 1t/ha wheat yield benefit on deeply compacted and acid yellow sand” (Blackwell, 2013)
Our Agrowplow AP91 features a shallow leading tine design and consists of a single row of shallow leading tines working in-line and ahead at depths of up to 450mm. This then reduces the draft force required by the following tines, set to penetrate up to 600mm. Studied by the team at the Department of Agriculture and Food, the leading tine configuration improves the towing ability and reduces fuel and time costs by reducing the draft force / pulling power required to pull the ripper.
“Recent DAFWA research demonstrated that the addition of a single, shallow leading tyne working in-line and ahead of a deep-ripping tyne could reduce the ripping draft force on clay soils by up to 18 per cent and on sandy-textured soils by 10 to 15 per cent” (B, Isbister, 2015)
Soil Compaction- Background, DAGF-2015
Double-tyned ripper removes deep compaction, Isbister-2015
Thank you to the team from Department of Agriculture and Food WA for permission to publish their findings
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