institute of Agricultural Research and Development NEIKER-Tecnalia. Spain 2Department of Plant Biology and Ecology University of the Basque Country, Spain 3Institute of Grassland and Environmental Research IGER-North Wyke, UK
Agricultural activities are significant producers of nitrous oxide (N2O) emission to the atmosphere (Johnson et al., 2007; Ugalde et al., 2007). That is, about 58% of total anthropogenic N2O emissions are caused by agriculture (IPCC, 2007). The main cause of agricultural increases in N2O is the application of N fertilizers and animal manures. Nitrous oxide is a long-lived greenhouse gas in the atmosphere with 296 times the global warming potential of CO2. Denitrification is credited as the primary producer of N2O (Johnson et al., 2005), which is generally favoured in poorly aerated soils with high NO3-concentrations (Van Groeningen et al., 2005). Currently, about 32% of the agricultural land in the EU is used for grassland production (Eurostat, 2005). The response of grassland to fertilizer N is greater than that of most other crops due both to its long growing season and to being harvested as vegetative growth (Whitehead, 1995). In the Basque Country, around 36% of agricultural land is occupied by grassland, and there is a high risk of N2O losses by denitrification due to high rainfall, typically in excess of 1000 mmyr-1, and warm temperatures, especially in spring and autumn when fertilizer is applied (Estavillo et al., 1994). Besides, the current dairying model is still developing towards an intensified dairy production system, resulting in increases in generation of animal manure, which may be also a significant source of harmful nutrient emissions into the environment if handled improperly. Also, the mountainous orography characteristic
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