ICONICA

To make Europe a climate-neutral continent by 2050 while ensuring food security, sustainable agricultural soil management practices must be introduced. Improved soil organic carbon (SOC) storage (sequestration) could reduce the increase in atmospheric CO₂ concentration. The long-term sequestration of SOC depends on many factors, especially interactions with other nutrients. The coupled Carbon-Nitrogen-Phosphorus cycles mediate soil organic matter formation and turnover. Soil phosphorus (P) is a key nutrient for plant growth. Limiting P content can reduce plant and microbial biomass in the soil and affect the sequestration of SOC. Altered soil P content affects microbial composition and activity, which are thought to control certain transformation pathways in the soil carbon and nitrogen cycles and influence the stabilization of GHG emissions, SOC, and nutrients.

The "ICONICA" project (ICONICA: Impact of long-term phosphorus additions on Carbon sequestration and Nitrogen Cycling in Agricultural soils) is using a series of long-term experiments on phosphorus fertilization in the EU and New Zealand to investigate the impact of varying soil P availability on SOC sequestration and GHG emissions, as well as on the carbon-nitrogen cycle in soils. Soil microbial processes associated with varying P availability in managed grassland and cropland systems will be quantified to identify mechanisms for SOC and nitrogen sequestration.

At the Institute of Plant Ecology, stable isotope techniques (labeling with ¹³C and ¹⁵N) are being applied in laboratory experiments to determine how long-term management of P fertilizers at different intensities controls soil C and N cycling and associated greenhouse gas emissions. The climate-relevant fluxes of the greenhouse gases N₂O and CO₂ from soils are measured. C and N dynamics will be assessed as a function of long-term P fertilization at different intensities. Results of ¹⁵N tracing will be matched with associated N₂O emissions and C transformations to determine soil C losses and potential C stabilization affected by long-term P fertilization. Data generated by ICONICA will be used to determine optimal soil P levels and corresponding fertilizer recommendations for farmers that include optimal SOC sequestration and minimization of GHG emissions while maintaining crop yields of various agricultural soils.