Iconica: Impact of Long-Term Phosphorus Additions on Carbon Sequestration and Nitrogen Cycling in Agricultural Soils (New Zealand)

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.