Soil is the largest reservoir of carbon (C) in the terrestrial biosphere and a slight variation in this pool could lead to Substantial changes in the atmospheric CO2 concentration, thus impact significantly on the global climate. Cultivation of natural ecosystems has led to marked decline in soil C storage, such that conservation agricultural practices (CAPs) are widely recommended as options to increase soil C storage, thereby mitigating climate change. In this review, we summarise soil C change as a result of cultivation worldwide and in Australia. We then combine the available data to examine the effects of adopting CAPs on soil C dynamics in Australian agro-ecosystems. Finally, we discuss the future research priorities related to soil C dynamics. The available data show that in Australian agro-ecosystems, cultivation has led to C loss for more than 40 years, with a total C loss of approximately 51% in the surface 0.1 m of soil. Adoption of CAPs generally increased soil C. Introducing perennial plants into rotation had the greatest potential to increase soil C by 18% compared with other CAPs. However, the same CAPS Could result in different outcomes on soil C under different climate and soil combinations. No consistent trend of increase in soil C was found with the duration of CAP applications, implying that questions remain regarding long-term impact of CAPs. Most of the available data in Australia are limited to the surface 0.1 to 0.3 m of soil. Efforts are needed to investigate soil C change in deeper soil layers in Order to understand the impact of crop root growth and various agricultural practices on C distribution in soil profile. Elevated atmospheric CO2 concentration, global warming and rainfall change Could all alter the C balance of agricultural soils. Because of the complexity of soil C response to management and environmental factors, a system modelling approach Supported by sound experimental data would provide the most effective means to analyse the impact of different management practices and future climate change on soil C dynamics. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
