Iconica: Impact of Long-Term Phosphorus Additions on Carbon Sequestration and Nitrogen Cycling in Agricultural Soils
Greenhouse gas (GHG) emissions pose a challenge to the modern world and further generations. One possible strategy for climate change mitigation is enhancing soil carbon (C) sequestration by promoting C uptake from the atmosphere and storing it in the form of soil organic matter (SOM) to reduce increases in atmospheric carbon dioxide (CO2) concentration. A pivotal process hypothesized to control soil organic C (SOC) sequestration is the soil microbial C pump which is based on microbial decomposition of organic litter and release of new organic substances. The coupled Carbon-Nitrogen-Phosphorus cycles (CNP) mediate SOM formation and turnover, for example, soil phosphorus (P) is a key nutrient for crop growth and P limitation can reduce plant and soil microbial biomass affecting SOC sequestration. In vitro studies have shown that soil P concentration significantly affects emissions of nitrous oxide, a potent greenhouse gas, soil nitrogen (N) mineralisation, N immobilisation and C fluxes. Varying P level impacts on microbial composition and activity of organisms, which are predicted to control specific transformation pathways within the soil C and N cycles, will influence the stabilisation of GHG emissions, SOC and nutrients. While the stoichiometric constraint of P on plant growth is known, the effect of this constraint on other soil processes at different P levels is uncertain, particularly in relation to GHG emissions and N and C cycling. Agricultural soils are considered likely storage sites for carbon making them a potential tool for climate change mitigation. An increase in SOM has additional benefits, including improvements in soil fertility, water retention and texture, which supports crop productivity and biodiversity. Restoring and maintaining SOM can be achieved by adopting management practices which increase C sequestration and stabilize C in the soil matrix. This relies on development of tools in the form of agricultural practices that favour soil C sequestration, such as long-term P or N fertilization. To predict the effect of certain agricultural management on SOC, the mechanisms of C transformations in soil must be understood. At its core, we must study soil microbial communities that mediate C transformations. Exploring the mechanisms of C cycle can lead to the development of novel sustainable techniques for land management that may reduce GHG emissions and favour soil fertility. The key to understanding these processes is integrating the role of microbial communities.