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The use of subtropical perennial grasses in temperate grazing systems is increasingly being promoted for production and environmental benefits. This study employed a combination of elemental and stable isotope analyses to explore whether pastures sown to either kikuyu (Pennisetum clandestinum) or a combination of panic (Panicum maximum) and Rhodes grass (Chloris gayana) could increase soil organic carbon (SOC) levels in five regions across southern Australia. Carbon was sequestered under kikuyu at a rate of 0.90 ± 0.25 Mg C [ha.sup.-1] [year.sup.-1] along the south coast of Western Australia. Lower but still significant sequestration rates were found for kikuyu in South Australia (0.26 ± 0.13 Mg C [ha.sup.-1] [year.sup.-1]). No changes in SOC were found for panic-Rhodes grass pasture systems in the northern district of Western Australia. Additionally, we found no changes in SOC when kikuyu-based pastures were established on formerly cropped paddocks in the Namoi Catchment of New South Wales. Stable isotope results corroborated these findings and suggested that, where SOC has accumulated, the gains have been dominated by SOC derived from the perennial vegetation and have been concentrated in the upper 10 cm of soil., Introduction The introduction of perennial grasses, especially in lower and more seasonal rainfall zones, can provide production and environmental benefits (Sanford et al. 2003; Nichols et al. 2012). As such, [...]

Here we take advantage of the stable carbon isotope shift that occurs when a [C.sub.4] plant is sown into a soil previously dominated by [C.sub.3] vegetation, to explore the movement and fate of newly sequestered soil organic carbon (SOC) following establishment of subtropical perennial pastures in temperate regions of Australia. In kikuyu-based pastures up to 33 years of age, SOC accumulated exclusively in the coarse size fraction (>50 µm) in the sandy soils of southern Western Australia. In South Australian loams, regardless of pasture age, new SOC was found to accumulate in both the coarse and fine (, Introduction There is much interest in sequestering carbon in agricultural soils as a greenhouse gas abatement strategy. A significant body of literature (e.g. Conant et al. 2001; West and Post [...]