Yvonne Y. F. Chang1
1 CSIRO Agriculture & Food, Australian Cotton Research Institute, Narrabri NSW 2390, email@example.com
Maintaining or increase levels of soil organic carbon (SOC) is necessary for ensuring ongoing agricultural productivity. Longevity of SOC is dependent on (1) the composition of carbon molecules within the SOC pool, and (2) protection of SOC from degradation through chemical and/or physical protection (e.g. physical protection of SOC from aerobic degradation within micro-aggregates). Melanised root-associated fungi (MRAF) may increase and stabilise SOC through: (1) the transformation of less stable carbon compounds (e.g. polysaccharides, plant-based carbon) to more stable carbon compounds (e.g. chitin, melanin), and (2) the formation and stabilisation of soil aggregates, and resultantly stabilisation of SOC within aggregates. The aim of this experiment was to test whether MRAF increase SOC within a carbon-poor soil. A glasshouse, pot experiment was set up with Gossypium hirsutum (Sicot 74683F) as the host. Pots were inoculated with one of two Control treatments (sterilised millet or wheat seed), or one of four fungal isolates (48B, 274A, C004.2 of NV016.17). Total SOC and SOC within each aggregate fraction was not significantly different between treatments; and total SOC didn’t significantly change over time. Whilst total SOC remained unchanged, the proportion of SOC within the micro-aggregate fraction was significantly greater 75 days after seedling germination compared with initial soil. Changes in the location of SOC suggest the presence of an active microbial community, transforming and stabilising pre-existing carbon compounds, throughout the experimental period. Variation in SOC between pots may be due to variation in the growth, colonisation and activity of target and non-target microorganisms. Understanding the growth and activity of the soil microbial community may enable better SOC management strategies to be developed.