Figure 62 Relative contribution of N sources to N2O emissions from pastoral and confinement or hybrid livestock systems

Source: Based on data from the national inventory reports of New Zealand (Ministry for the Environment, 2008) and the US (Environmental Protection Agency, 2008)

Globally, N2O emissions from grazing are estimated to contribute 45 per cent or more of total livestock emissions, while emissions from manure collected in confinement systems and following application to land are estimated at around 20 and 10 per cent, respectively (Oenema et al, 2005; Steinfeld et al, 2006). Emissions from N fertilizer use on pastures are around 10 per cent of global livestock N2O emissions, largely from high-rainfall dairy production systems. The most effective options for reducing N2O emissions from livestock systems are those that target the main source of N2O for a given system. This chapter describes:

• current approaches for estimating N2O emissions from livestock systems.

• N2O and total greenhouse gas profiles from different systems.

• a summary of current N2O mitigation strategies for different livestock systems; and

• estimates of the impact of a range strategies on total greenhouse gas emissions.

Year-round grazing

Confinement or Hybrid system

■ Uring/dung id Fertiliicr □ F ¡! irr I; Manure

Year-round grazing

Confinement or Hybrid system

The chapter concludes with a discussion of the future trends in livestock agriculture covering issues such as greenhouse gas intensity versus total greenhouse gas emissions, impact of climate change, and accounting for mitigation strategies.

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