DPIRD experiment reveals the best techniques for water repellent sand at Moora
Project name
Benefit of repeated amelioration
GRDC Code:
DAW1902-003RTX
Research funded by DPIRD and GRDC co-investment in soil amelioration and re-engineering project
Confronting soil water repellence
Soil water repellence is caused by an accumulation of waxy organic matter on the surface of soil particles and is more pronounced in sandy-textured topsoils.
This results in uneven wetting of the soil profile and leads to delayed or staggered emergence of crops, pastures, and weeds, which could potentially lead to diminished productivity.
Additionally, it triggers nutrient deficiencies as the dry repellent soil impedes nutrient uptake by plants, resulting in deficiencies in phosphorous, copper, zinc, and manganese.
Various factors such as: dry autumns, dry sowing practices, reduced cultivation, and certain seeding methods exacerbate water repellence.
To address this challenge, researchers have tested agricultural practices such as improved furrow sowing techniques, soil wetting agents, occasional deep cultivation, and the application of clay spreading or clay delving methods over time.
Experiment methodology
This experiment was conducted on water repellent, yellow deep sand at Moora, with the aim to identify the best combination/s of clay application rate, method of incorporation and repeated strategic deep tillage, to optimise long-term crop production benefits.
It was laid out in 3 randomised blocks, with plots measuring 18m wide and 15m long.
The site was deep ripped to approximately 40cm prior to the claying and incorporation treatments being applied in 2016.
In the same year, subsoil clay was applied at different rates perpendicular to the direction of seeding, using a multi-spreader.
Clay spreading was followed by either no further incorporation or incorporation, from low to high degree of mixing, using:
- Offset disc
- Rotary spader (standard speed)
- Rotary spader at half-speed for extra mixing
These were applied perpendicular to the clay spread strips in the direction of seeding.
The site was sown with the four-year crop rotation of barley, lupins, wheat and canola.
In 2020 each plot was split for 3 new treatments:
- Nil (original 2016 treatment only)
- Deep ripped to 40cm
- Deep ripped to 40cm then rotary spaded to 35 cm.
The same 4-year crop rotation occurred following the 2020 tillage treatments which were carried out prior to sowing.
Results
Crop establishment was clearly improved through the clay application but was even more evident through the spading tillage treatment.
This resulted in higher grain yield being achieved on these spading treatments every year that this experiment has been in operation.
For this repellent deep sand, spading has proven, over 8-seasons, to be the most effective and profitable amelioration method. This spading alone, without any clay applied, has resulted in a cumulative net benefit of $1480 per hectare profit when compared to the control treatment.
Repeat spading has had significant additional yield benefits and resulted in a further increased cumulative net benefit of just under $400 per hectare on top of the original spading treatment.
Project collaborators
Lawson Grains and manager Mark Drake for hosting and managing the site.
More information
Click here to read more in the Soil Quality: 7 Soil Water Repellence on Apple Books
Click here to read publication ‘Assessing options for managing water repellent gravel soils’
Contact
Chad Reynolds
DPIRD Research Scientist
E: Chad.Reynolds@dpird.wa.gov.au
P: (08) 9956 8573