Miss Ivanah Oliver1, Dr Richard Flavel1, Dr Oliver Knox1, Dr Brian Wilson1,2
1University Of New England, Armidale, Australia, 2NSW Office of Environment and Heritage, Armidale, Australia
X-ray computed tomography (xCT) has enhanced our understanding of how soil structure impacts the spatial distribution of root systems. Pore space characteristics and presence of root channels are two physio-chemical properties of the soil which influence spatial root distribution. Our current understanding of how regularly roots utilise a single pore space seasonally is limited. This in turn has implications for resource depletion (e.g. phosphorus), accumulation of plant products (e.g. root exudates) and physical legacy. This study evaluated the occupancy of an actively growing root system in pre-existing root pore spaces and the potential for root derived microbial and exudate hotspots.
The experiment involved growing Sorghum (Sorghum spp.) in pots for two 8 week growth periods separated by a 12 week decomposition period. At the beginning of the decomposition period plant above-ground biomass was removed and roots were left to decompose naturally. X-ray computed tomography was utilised to image a small section of the pot for determination of the spatial distribution of roots and pore spaces. The images collected at the end of each growth and decomposition period were then overlayed and compared to determine the proportion of roots that reoccupied the pre-existing root pore spaces.
Under the experimental conditions of this study, the sorghum roots did not appear to preferentially occupy the root channels created by the previous crop. The study findings will be utilised to better explain the broader implications for nutrient and water acquisition, microbial and exudate hotspots, and soil physical properties.
Ivanah is a PhD candidate at the University of New England. Her research focus is on root carbon inputs into the soil.