The Potential for Carbon Sequestration in Australian Agricultural Soils Is Technically and Economically Limited.

Do Australian agricultural soils play a role in climate change process and mitigation by sequestering carbon? The net carbon exchange of agro-ecosystems depends on the balance between carbon gain (input of crop residues) and carbon loss (decomposition of soil organic matter). There has been an ongoing debate globally as to whether agricultural practices can increase soil carbon stock. Australian soils are much older when compared to many soils in the northern hemisphere. Nutrient deficiency, salt accumulation and undesirable climate conditions probably restrict the potential of soil carbon sequestration in Australia. However, a quantitative review on the effects of agricultural practices on soil carbon change in Australian cropping systems is lacking. In this meta-analysis, we investigated the effect of agricultural practices viz. zero or reduced tillage, residue incorporation, rotation history and nitrogen fertilizer application on soil carbon change in Australian cropping systems. The potential patterns of variation in the effects of agricultural practices were also assessed by including categorical variables in the meta-analysis models. These variables include soil depth, cropping duration, soil clay content, and geographic location. The objective of this study was to systematically synthesize and quantify the effects of agricultural practices on soil carbon change in Australia. The potential, if any, of agricultural management practices on the mitigation of greenhouse gas emissions from Australian cropping systems will be discussed.