Soil Aggregate Dynamics, Particulate Organic Matter and Phosphate under Dryland and Irrigated Pasture

Soil aggregate formation and turnover affects the rate of occlusion or release of soil organic matter and therefore the availability for mineralisation or stabilisation of soil carbon (C) and phosphorus (P). Furthermore, differences in soil type, management and the quantity and quality of organic inputs can affect aggregate turnover rates (Six et al., 2000). Under pastoral farming the ratio of coarse particulate organic matter (inter-POM) inside macroaggregates but outside microaggregates to fine POM (intra-POM) within microaggregates may provide an indication of physical processes influencing mineralisation and stabilisation of soil C and organic P (Po). Our aim was to determine the coarse and fine POM and associated C and P contents in water stable macro and microaggregates under long term irrigated and dryland pasture grazed by sheep