A synthesis on carbon, nitrogen and greenhouse gas budgets of four agricultural sites across Europe

Although croplands are net sinks of carbon dioxide (CO2), when accounting for the imports with manure and harvest, they predominantly act as net sources of carbon and nitrous oxide (N2O) to the atmosphere (Ceschia et al., 2010; Kutsch et al., 2010). Flooded crops (rice) are sources of methane (CH4Methods/Approach ). In addition, croplands receive large amounts of nitrogen either by mineral or organic fertilization. The carbon (C), nitrogen (N) and greenhouse gases (GHG) budgets of four croplands across Europe (Gebesee, DE; Grignon, FR; Borgo Cioffi, IT; Castellaro, IT) over a five-year period are compared. These four sites span across a temperature and a precipitation gradient. The links between the nitrogen and carbon budgets as well as their respective uncertainty are analyzed and the consequences of the budgets in terms of ecological impacts are discussed.