23. Nitrous Oxide (N₂O) Emissions from Forests, Grasslands and Agricultural Soils in Northern Spain

This chapter presents a study of nitrous oxide (N₂O) emissions from (a) forest soils (Pinus radiata and Fagus sylvatica) at different growth stages and from (b) grassland and agricultural soils in the edapho-climatic conditions of northern Spain. A mixed clover–ryegrass sward, wheat and oats crops were fertilized with ammonium sulphate nitrate, cattle slurry and/or sewage sludge. The mitigation effectiveness of the nitrification inhibitor (NI) 3,4-dimethylpyrazole phosphate (DMPP) was also assayed. Nitrous oxide losses from forests in northern Spain are limited by nitrogen (N) deposition, resulting in lower losses than temperate forest in the rest of Europe. The NI DMPP seems to be an advisable strategy to mitigate N₂O emissions, both in grasslands and in crops. Sewage sludge application should be further studied but significant reduction in N₂O emission is possible with DMPP. The results presented suggest that an emission factor around 0.1–0.3%, depending on crop type, time of year and fertilizer type, should be applied for this area instead of the default value of 1% suggested by the Intergovernmental Panel on Climate Change (IPCC).