CaCO3 in agroecosystems as a source of atmospheric CO2 by nitrogen fertilization

• Applicant: Dr. Kazem Zamanian, Ph.D.
• Subject Area: Soil Sciences
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 441739623

Nitrogen (N) fertilization and transformation of applied N through nitrification produces acidity in soils. This acidity in calcareous and limed soils is neutralized via carbonates (mostly CaCO3) dissolution leading to release of significant CO2 amounts to the atmosphere. So far, the importance of CO2 emission from CaCO3 due to N fertilization is neglected and so, the involved processes, the environmental conditions and management practices controlling the rates of CO2 emission from CaCO3 are poorly investigated. These issues will be addressed in this proposal through 6 work packages (WP) of lab- (WP1-3 and 5) and field works (WP4) as well as modelling (WP6) to determine and to predict CO2 emission from CaCO3. δ13C natural abundance will be used to differentiate between the CO2 sources i.e. CaCO3 or CO2 from root and microbial respiration. The effects of quality and stability of soil organic matter (WP1) and plant nutrient balance (WP2) will be investigated via comparing organic and mineral fertilizers. Formation of carboxylic groups and analyzing H+ distribution from fertilization point will be traced using the planar optode pH mapping system. WP3 addresses the effects of soil redox potential and contribution of Fe2+ and Fe3+ on CO2 emission out of carbonates. WP4 examines rhizosphere processes and N use efficiencies of plant species. WP5 focuses on contribution of subsoil carbonates using dual labeled (15N and 2H) urea and tracing downward movement of nitrate and H+. In WP 6 key influencing parameters on CO2 emission form CaCO3 (soil water contents, Ca2+ concentrations in irrigation water, N fertilization rates, plant species, temperature and fertilization periods (10 to 100 years)) will be implemented into a process-based model in Hydrus 1D. The results will distinguish processes and mechanisms of CO2 efflux form CaCO3 and will emphasize that improving N fertilization management prevents long-term CO2 emissions.

• DFG Programme: Research Grants