Investment in science and industry development key to profitable agrifood sector 2

Collaboration generates abundant opportunities for tackling repellent soils

Science team: Dr Stephen Davies (project leader), Giacomo Betti, Dr Paul Blackwell, Chad Reynolds, Joanne Walker, Dr Geoff Anderson, Dr Craig Scanlan, Glenn McDonald, Grey Poulish, David Hall, Tom Edwards.

The combined forces of three universities, the CSIRO and leading grower groups have created an abundance of opportunities for the DAFWA-led GRDC research project into soil water repellence.

For crop production, the consequences of water repellency can be huge. Repellency can stress plants from the outset, resulting in poorer yield quality, run-off, loss of nutrients and poor weed control.

Together with the CSIRO and Murdoch University, we are examining the chemistry and nature of water repellence and how it impacts on crop growth, as well as researching a wide range of practical management techniques and their agronomic implications.

Understanding the chemistry and variability in expression of water repellence will help us to target management practices effectively. For example, recent research into soil wetters has found they can be very effective on repellent forest gravels and that some products can also work well when used in formulations with other liquid fertilisers and banded near the seed.

DAFWA project researchers have also collaborated with Australia’s leading agricultural research engineers at UniSA to better understand and improve the use of strategic tillage implements, such as mouldboard and one-way ploughs, to better overcome a range of soil and agronomic constraints.

The project has had a leading role in helping develop capacity in future soils research by appointing three PhD students, two post-doctorates and two new DAFWA soils research positions, at Geraldton and Esperance.

Providing Murdoch University and UWA PhD students with an opportunity to work in close collaboration with DAFWA gives them the capacity to network with and understand the broader issues being faced by grain growers, to benefit their research and communication.

Partnerships with four leading grower groups across the grainbelt also provide opportunities for grower-focused communication, local demonstrations and a vital conduit for feedback and knowledge from industry back to the researchers.

New research will develop a better understanding of the chemistry of water repellence on a range of soil types, how it is distributed within paddocks and its impact on the availability of nutrients both in space and over time.

Ongoing research on management options on a range of soil types and environments will provide improved clarity for growers to confidently implement effective management practices.

HIGHLIGHTS

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  Extensive collaboration with universities is providing opportunities to train soils researchers and undertake fundamental research into understanding the water repellence problem, its consequences and management.
  
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  Research results show that amelioration of strongly repellent soils can compound long-term benefits through:
  

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  improving establishment
  
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  reducing other soil constraints
  
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  enabling more efficient use of water and nutrients
  
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  reducing wind erosion risk
  
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  enhancing weed control.
  

Funding and collaborators

GRDC, CSIRO, MU, UniSA, West Midlands Group, SEPWA, MIG, SouthernDIRT

Right: DAFWA Research Officer Steve Davies discusses the challenges of growing crops on a water repellent forest gravel soil near Kojonup.

Clay: the soil solver for water repellence?

Science team: Dr Stephen Davies (project leader), Giacomo Betti, David Hall, Chad Reynolds, Joanne Walker.

Water repellent soils are a major production constraint on many sandy and gravelly textured soils across WA. These soils are challenging to establish crops and achieve adequate weed control. Often the only way to correct this water repellence is by applying and incorporating large amounts of clay. 

The practice of claying, which incorporates clay-rich subsoil into sandy topsoil either by clay spreading or delving, is one of the most effective methods to correct water repellence in the long term. It has been used by some growers in Australia for more than two decades.

By mixing clay into water-repellent sand, soil wettability improves significantly and dry patches (even after heavy rains) occur less frequently. Crops establish better and plant growth improves. Clay also benefits the soil by increasing its capacity to hold water and nutrients and reducing the risk of wind erosion.

Over 10 million hectares of agricultural land is affected by water repellence in the south-west of WA alone. We assess that claying will be an important corrective to repellent soils in the grainbelt in the long term, and in the drier central and northern regions in particular.

Growers in WA have been slow to adopt claying. This is partly due to the high initial costs of claying and partly because early anecdotes implied the risk of yield loss. The practice is limited and still perceived negatively by some growers.

As part of the GRDC-funded water repellence project, DAFWA initiated new long-term trials in 2016 assess the practice under local conditions.

To account for different soil types and climates, three trials have been established –– clay spreading at Badgingarra and Moora (deep sands and sandy gravel soils), and clay delving at Esperance (texture-contrast soil).

All trials have been designed to compare different rates of subsoil clay combined with different tillage methods for its subsequent incorporation into the topsoil (spader, offset discs, one-way plough) in the same paddock.

The aim of the trials is to better evaluate the benefits of adding subsoil clay to remediate repellent soil and improve crop establishment.

R&D activities will focus on two main aspects:

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  economics – by comparing the cost-effectiveness of the treatments over a four-year period
  
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  efficiency – by collecting data at different stages of plant growth to measure the impact of the treatments on soil water and nutrient availability.
  

Future work will focus on fine tuning the most cost-effective claying practices outlined by the results of the current trials. At the completion of the trials, we aim to produce best-practice guidelines for growers interested in claying.