Greener pastures for salt-affected island

As part of an industry-supported honours project, Bachelor of Science (Applied Sciences) (Honours) student Peter Matthews has been working closely with Westernport Water and Bimbadeen Farm to investigate the use of biosolids to remediate agricultural land affected by dryland salinity.

The project has tested the use of organic matter obtained from a local sewage treatment process, known as biosolids, on a portion of salt-affected farming land on the island.

“At Bimbadeen Farm the areas which are most salt-affected are low lying areas where the water table is quite shallow,” Matthews said.

“These areas have very low productivity, whereas much of the other soil on the farm that has undergone remediation over the past few decades has improved productivity.”

The idea behind adding biosolids is to improve the soil’s structure and stability while excess salts are leached away.

“It’s hoped that a lower concentration of salts together with the addition of macro and micro nutrients from the biosolids will allow pasture species to establish,” he said.

“In addition to improving the structural stability, the increase of calcium from the biosolids may also assist in the leaching of sodium ions which are the main cause of poorly-structured dispersive soils.”

Similar findings are evident in studies previously undertaken in Mediterranean countries such as Spain, however this is the first known field trial specific to Victorian or Australian soils.

Matthews explained that current methods to promote leaching of soluble salts involve the use of heavy machinery and chemical amendments, which can be costly.

“The addition of inorganic chemical fertilisers is often needed to increase productivity on these soils – such methods can be expensive and also carry a large carbon footprint,” he said.

“The advantage of using biosolids is that it’s a locally produced waste product that is a valuable source of nutrients with the potential to be an economic and sustainable solution for farmers across Victoria and Australia.”

The project is a collaboration between RMIT, Westernport Water, Bimbadeen Farm and Transpacific Industries, and is coordinated by Professor Barry Meehan from the School of Science.

“Through our ongoing partnership with South East Water and the Transpacific Group, we were able to work with Westernport Water who jointly sponsor the honours project with Transpacific,” Meehan said.

“Our industry partners saw the project as a valuable opportunity to explore the potential for biosolids in remediating salt-affected land, and if successful, to roll out the technique to other farmers around Phillip Island and indeed, the wider region.”

In addition to Matthews, the project involves three teams of undergraduate students who have been undertaking soil surveys on Bimbadeen Farm.

“The project has provided students with hands-on experience with salinity issues on a farm and the opportunity to engage with industry,” Meehan said.

"One of the students has also secured a job, based largely on the experience gained as part of his work with the Phillip island project."

Matthews agreed the project is a valuable opportunity to work with a variety of people from a number of industries.

“Undertaking a real-world research project and having to present findings to stakeholders on a regular basis has provided me with industry links that will help me when I graduate,” Matthews said.

“I’ve received lots of assistance from my team of RMIT undergraduate and postgraduate students during sampling and laboratory work and I’ve developed key leadership skills along the way – this has all been fundamental in building my confidence.”

Although there have been no official outcomes for the project as yet, there has been great interest in the local community of Phillip Island and across Victoria.

“Provided the trials are successful, the treatments applied will provide the ideal levels of concentration needed to produce a beneficial change in the soil environment for the growth of pasture species,” Matthews said.

“Preliminary results indicate that the application of biosolids is having a positive effect on crop yields, however the effects on the soil environment are still to be determined.”

Matthews will spend the rest of the year analysing results in the lab and writing his thesis, and hopes to continue his research on the potential of biosolids into the future.

“Peter has had a very rich experience liaising with the farmer regularly, presenting his findings to the stakeholders, experience in soil and plant analysis, and so on,” Meehan said.

“This is work integrated learning at its best – and everyone’s a winner.”

Story: Rebecca McGillivray