IYS Soil of the Month - October
Dr Samantha Grover is a postdoctoral researcher in the Soil-Plant Interaction Group at La Trobe University. Currently working out how to store more carbon in the sandy soils of the Western Australian wheatbelt, Sam fondly recalls the damper climes of the Australian Alps, where she carried out field work for her PhD on the carbon and water dynamics of peat soils.
If you had to choose a special Australian soil type what would it be?
Organosol, or, as I like to refer to it, peat.
What are the main properties of this soil type?
Organosols are special because their parent material is plants, unlike the more extensive mineral-based soils that cover the majority of Australia. Organosols occur where the rate of decomposition of organic material is slower than the rate at which new organic material is added to the system. This can be in hot wet climates, like Indonesia, where plants grow very fast, or cold wet climates, like Russia, where decomposition is slow. In a hot dry country like Australia, peat soils are understandably rare. However, in the damp and cool Alps, peatlands are locally common and form a key part of the hydrology of some of Australia’s most efficient catchments. Organosols also store large amounts of carbon, due to their organic heritage.
Why do you find this soil type particularly interesting?
Organosols are fascinating! These soft wet soils can contain less solid material than milk and yet you can, carefully, walk across their surface. Whole cows, even whole tractors, have disappeared into peats, when the unwary fail to consider their unique nature. Coming from a chemistry background, I was immediately hooked by the elegant linkages between the extent of decomposition of the organic material in peats and their hydrologic properties. During my PhD research I attempted to quantify these relationships, combining state of the art solid state 13C nuclear magnetic resonance with traditional soil physics techniques. More recently organosols have connected me up with some fascinating global-scale projects. After reading my PhD research, three groups have invited me to collaborate and so now I am involved in peatland studies using NMR and microbiology to better understand the distribution, function and resilience of peatlands world-wide.
Do the properties of this soil type have consequences for its management, e.g. in terms of land use,
soil quality, conservation …
Organosols form in wet conditions, but when people want to use these soils they inevitably drain them. As these organic soils dry out they change considerably and irreversibly, and managing them is an ongoing challenge. We visited organosols in Germany that were drained over a thousand years ago by Dutch settlers on the field trip of the 5th International Symposium on Soil Organic Matter. While these soils have subsided by several meters and released tonnes of carbon into local waterways and the atmosphere, they are still productive grazing and cropping lands with high levels of organic matter. Closer to home, drained peat swamps in the Kooweerup region of Victoria are renowned asparagus-growing soils. In the Australian Alps, the focus of management is on restoration, as these peatlands are protected by legislation and have been extensively degraded by grazing and fire.
Can you tell us your most memorable story concerning this soil type?
Hmm, how to choose? Leaches on eyelids, snow during field work at New Years’, midges and fine whisky in the Scottish highlands. Organosols have lead me on many adventures but I feel the best is yet to come as I plan to sample Antartic organosols on next year’s Homeward Bound expedition. Stay tuned for more details!