Estimation of CO2 Emissions From Cropland in Norway.

Monitoring changes in soil organic carbon (SOC) is not only linked to atmospheric CO₂ dynamics, but also to the sustainability of agricultural systems, maintaining food security, reducing water pollution and soil erosion. In accordance with the methodology of the Intergovernmental Panel for Climate Change (IPCC), we developed a Tier 2 method for estimating CO₂ emissions from cropland on mineral soils in Norway and compared the results with those of a Tier 1 method. As in most countries, long-term C stock or emission data sets useful for generating factors are scarce in Norway. We used a soil C balance model (ICBM) to calculate country-specific C stock change factors for relevant management systems. Agricultural activity data for 31 agrozones, from 58 ºN to 71ºN, was applied to estimate annual net CO₂ emissions from 1999 to 2009. Calculated annual net emissions were larger when estimated by the Tier 2 method than Tier 1 because i) Tier 2-generated stock change factors for crop rotations with animal manure application were larger than the Tier 1 default values and ii) major changes in agricultural management during the inventory period led to a reduction in manure availability. We conclude that model-based Tier 2 methods are promising when empirical data are limited, but activity data, especially regarding animal manure practices (application rates and crop rotation preferences) are crucial for emission estimates by the IPCC methods.