Evaluation of the factors controlling nitrogen oxide emissions in meadowlands

Agriculture is responsible for 8% of the total emissions of greenhouse effect gases and so, given the EU adhesion to the 1997 Kyoto protocol, it is obliged to assume a certain percentage in the reduction of these emissions. 41% of nitrous oxide (N2O) emissions of human origin in Europe comes from agriculture. The soil, through microbic processes of nitrification and denitrification, is deemed to be mainly responsible for these N2O emissions, contributing to NO emissions also.

Meadowlands form a system with a high potential for the emission of these gases, given their high quantity of organic material and the high levels of fertilisation to which intensive agriculture subjects them. In this study the following factors in N2O and NO emission in meadowlands have been investigated: fertilisation, the water content in the soil, tillage and the use of nitrification inhibitors.

The results obtained indicate that the clay soils studied in the Basque Country show a high level of nitrification. As a consequence, the Nitrogen from applications of organic residues is quickly transformed into a mineral Nitrogen which is susceptible to loss to the atmosphere in the form of oxides of Nitrogen and mainly as a consequence of nitrification. The addition of inhibitors of nitrification is a recommended practice for this type of fertiliser. The N2O emissions derived from mineral fertilisation with ammmonium calcium nitrate are mainly produced through desnitrification, and it is therefore recommended to adjust the mineral fertiliser rather than have to use it in conjunction with DCD. Practices like tillage have a negative effect, provoking N2O and NO emissions even over and above the levels recorded in highly fertilised but untilled areas. Given that it is common practice to dig up a field for the cultivation of forage maize, tillage using nitrogen-based fertilisation should be well-spaced so as to avoid high NO and N2O emissions