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BCIA’s annual program of postgraduate research scholarships is part of our commitment to strategic investment in skills development to secure the scientific, engineering and trades expertise required for the development of new low-emissions brown coal technologies.

In 2010, BCIA awarded five research scholarships to PhD candidates at top-ranking Australian universities. A sixth research scholarship was awarded late last year.

In this editionh of
Perspectives on Brown Coal, BCIA scholarship recipient, Karen Little from Monash University, provides an update on her PhD research project.

Sustainable Soil Health and Soil Carbon through Victorian Brown Coal-derived Products
By Karen Little, Monash University PhD Candidate and BCIA Scholarship Awardee

Australian agricultural soils can often contain low levels of humic substances, the stable decomposition products of organic matter, and this is thought to contribute to poor soil structure and reduced crop yields. Victorian brown coal is a rich source of stable humic substances, and has long been used as a soil conditioner. Worldwide, extracts of humic substances are used in biological farming to improve soil health and promote crop growth. However there are very few published studies on the use of brown coal or humates to improve crop growth, so the mechanisms involved are poorly understood.

My PhD project involves an investigation of the effects of humic substances on plant growth, in an effort to understand whether the positive effect is due to direct stimulation of the plant, or to increased activity of soil microbes, or to altered soil properties. I am doing this by studying the effects of commercial brown coal-derived products (BCDP) on the remediation of degraded soils and on the growth of pasture grass.

So far, my research has involved characterisation of a number of BCDP by examining their pH, conductivity, elemental content (including plant essential nutrients that may have been incorporated during formulation), humic acid and carbon content, and carbon stability. Knowledge of the product chemical and physical characteristics is important for identifying the factors that contribute to improvements in plant growth and/or soil health.

To test the potential benefits of these products to plant growth, two glasshouse based experiments were conducted. In the first experiment a number of BCDP were added at the manufacturer’s recommended rate to two soil types; an acidic sandy soil and a neutral loam soil.

Ryegrass and lucerne, which are pasture species typically grown in Victoria, were planted into BCDP-treated soils and harvested following an eight week growing period. While at these rates there was no benefit in terms of plant growth for these particular plant species, there were significant changes in the size of the microbial community. This is important because microbes represent a significant pool of carbon in the soil and play a strong role in soil structure and nutrient cycling.

To further explore the lack of any pronounced effect of the BCDP on plant growth, a second glasshouse study was undertaken to investigate three of the previously used products applied at a wide range of application rates. At a

number of rates positive growth responses were observed, coinciding with a degree of correction of soil pH. This is important because many plants are sensitive to changes in soil pH, and changes in pH can alter the availability of soil nutrients to the plant. Consequently, further investigation of the soil chemistry is currently underway.

To complement the glasshouse studies, field trials have been established on two grazing properties in south-east Victoria. This involved adding three BCDP at a range of application rates in replicated plots. Pasture growth, changes in soil carbon and soil nutrient status and responses by the microbial community are currently being monitored.

In the coming year, investigation will continue into whether the primary effect of the humate is on the plant, on the soil or a combination of both. Incubation studies in which BCDP is combined with soil in the absence of plants are planned to investigate the impact of humate application on soil properties, and the compositional and functional response of the microbial community using chemical and molecular techniques.

It is anticipated that experimental outcomes will help to better understand the effect of BCDP on plant growth. With an improved understanding of the fundamentals involved, it should be possible for manufacturers to develop more effective products and for farmers to make an informed decision of how BCDP could be integrated into their current management practices for improved crop production.

BELOW: Lucerne at six weeks growth in the glasshouse facility at Monash University, Clayton campus.

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