| Researcher(s) |
Stephen Davies (DAFWA) Laura Dorman (MIG) Debbie Gillam (DAFWA) Chad Reynolds (DAFWA) Jo Walker (DAFWA) |
|---|---|
| Year(s) | 2016 |
| Contributor | West Midlands Group |
| Trial location(s) |
Badgingarra, WA
Dandaragan, WA |
Assessing practical soil management options for overcoming severe water repellence on sandy gravels in the West Midlands.
On deep sandy profiles subsoil compaction and acidity are major constraints. At this site the limited cropping history resulted in an expectation that the site would not be compacted but compaction was severe, indicating how susceptible these pale sands can be to compaction. For many deep sands, liming followed by deep ripping with topsoil slotting may be one of the most economical ways of effectively overcoming subsoil compaction and acidity to depths of 40-60cm.
On severely repellent sands however, it may be that deep ripping alone is inadequate and options which overcome the repellence and assist with weed control while at the same time addressing subsoil compaction and acidity may be required to get sustained productivity benefits (Davies et. al. 2017). The impact of deep ripping on highly repellent soils is variable with anecdotal reports that ripping can sometimes worsen the expression of repellence and result in poorer crop establishment. Other reports indicate substantial productivity gains can also be achieved (Blackwell et. al. 2016). Deep ripping may help overcome soil water repellence by: 1) creating a rougher soil surface allowing water to pond and infiltrate over time; 2) loosening the dry topsoil making it a more effective mulch, reducing soil moisture loss from the subsurface soil; 3) delving some seams of subsoil to the surface which act as pathways for water entry, with some ripper tine designs and attachments facilitating this more than others. Conversely the negative effects of deep ripping can include: 1) enhanced drying of the repellent topsoil from the loosening action; 2) increased expression of the water repellence when the soil is ripped when it is quite dry. Repellence severity, or expression, is increased with these negative effects which was the case for this site. For other sites where repellence is more moderate any benefits of deep ripping may outweigh the negative impacts. The mixed effects of deep ripping on repellent soils needs further research to be better understood. It is likely that rippers with C-shaped or parabolic shaped tines with broader points and wider ‘face’ plates will achieve more subsoil delving into the topsoil. Some rippers can also be fitted with wings which can also increase the degree of soil mixing. A greater degree of subsoil delving could result in development of more effective infiltration paths and longer lasting reductions in topsoil water repellence.
In this study rotary spading and modified one-way ploughing were effective in improving water infiltration on severely repellent sand even if they did not remove the deeper compaction. Second-hand one-way disc ploughs have a relatively low capital and operating cost (Table 1) and are relatively cheap to modify into a simple but robust tool for partial soil inversion (Davies et. al. 2016), although good seed bed preparation is still essential.
| Lead research organisation |
Department of Agriculture and Food WA |
|---|---|
| Host research organisation |
West Midlands Group |
| Trial funding source | GRDC DAW00244 |
| Related program | N/A |
| Acknowledgments |
GRDC DAW00244 Repellence Project: DAFWA; Paul Kelly |
| Other trial partners | Not specified |
| Crop type | Cereal (Grain): Wheat |
|---|---|
| Treatment type(s) |
|
| Trial type | |
| Trial design |
| Sow rate or Target density | Not specified |
|---|---|
| Sow date | Not specified |
| Harvest date | Not specified |
| Plot size | Not specified |
| Plot replication | Not specified |
| Sow rate or Target density | 83kg/ha |
|---|---|
| Sow date | 20 May 2016 |
| Harvest date | Not specified |
| Plot size | 12m x 1200m |
| Plot replication | Not specified |
| Rainfall trial gsr (mm) | 413mm |
|---|
SILO weather estimates sourced from https://www.longpaddock.qld.gov.au/silo/
Jeffrey, S.J., Carter, J.O., Moodie, K.B. and Beswick, A.R. (2001). Using spatial interpolation to construct a comprehensive archive of Australian climate data , Environmental Modelling and Software, Vol 16/4, pp 309-330. DOI: 10.1016/S1364-8152(01)00008-1.
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