March Podosols - Dr Gillian Kopittke Queensland Branch President
During the International Year of Soils, each month we ask a soil researcher to select his or her favourite soil.
Dr Gillian Kopittke is the President of the Queensland Branch of Soil Science Australia and is a soil scientist with experience in consulting, industry and academia. Gillian has enjoyed practicing soil science on a diverse set of sites, ranging from an artillery base in the Netherlands to mine sites in central Queensland. Gillian currently uses her soil science skills directly for the petrochemical industry.
If you had to choose a special Australian soil type what would it be?
Podosols (previously known as Podzols)
What are the main properties of this soil type?
Podosols are usually sand textured soils and are typically well drained. In Australia, they often have a black or grey surface over a conspicuously bleached A2 horizon overlying the characteristic darker B horizon. Organic minerals and soluble metals such as aluminium and iron are leached from the A2 and precipitate lower in the profile, resulting in this enriched B horizon. Australian Podosols can be very deep, with the B horizons sometimes as deep as 25m in south-eastern Queensland.
Why do you find this soil type particularly interesting?
Australia has the largest Podosols in the world and the coast in southern Queensland forms the terminus of the longest downdrift sand system in the world. It’s on these sand dune systems that the Giant Podosols have formed over thousands of years. Many people would have walked along the beaches of Fraser Island and Cooloola Coast across the “coffee rock” not realising that they were walking on the B horizon of a giant soil profile. These soils remind me of holidays at the beach!
I was then also lucky enough to work on this soil type during my PhD in the Netherlands. It was interesting to compare these soils forming under different climatic conditions (coastal Queensland hasn’t reached minus 16⁰C any time recently).
Do the properties of this soil type have consequences for its management, e.g. in terms of land use, soil quality, conservation, …
In Australia, these soils often support a wide range of plant communities ranging from subtropical rainforests, to subtropical eucalypt forests and woodlands, to wallum heath and other coastal dune communities. Because they are nutrient poor and generally very acidic, they are not typically used for agriculture, with the minor exceptions being for some pine forest plantations. There is some interesting work being proposed by The University of Queensland which will use the long weathering history of these Giant Podosol (sand dunes) to investigate processes of dune building and erosion in relation to climate and sea level change over scales from decadal to multi-millenial
Can you tell us your most memorable story concerning this soil type?
I was working with this soil in the Netherlands on a Dutch army base. During my field work, I uncovered unexploded ordinance from WWII and had a chinook helicopter land in my field trial (with dutch soldiers crawling through the heath) – all while collecting soil respiration measurements from a Pozol.
Photo: Gillian collecting soil respiration measurements on a Dutch Podzol, Oldebroek The Netherlands (Photographer: Niina Al-Fossi)