Increasing food production - especially in the developing world - is imperative for the well-being of the present and future generations of poor farmers and consumers. Although we do not deny the urge for curtailing GHG emissions, the authors are convinced that any conceivable programme on mitigation of GHG emission from the agricultural sector has to be based on the premise of higher food production. As for a future agreement after the rather disappointing outcome of the United Nations climate change Conference of Parties (COP15) in Copenhagen, it will be crucial to converge the legitimate goals of increasing food security and reducing GHG emissions.

As long as food security is not compromised by GHG mitigation, the common denominator for mitigation options is the increase in resource-use efficiencies. This paradigm applies to all three cereal systems discussed in this chapter and, arguably, to the agricultural sector as a whole. The adoption of currently available best management practices for N management should be a good guideline for practices that reduce N2O emissions. However, what is regarded as a good agricultural practice varies somewhat from region to region, reflecting variations in local soils and climatic conditions.

We can conclude that, although there remains large uncertainty in N2O emissions from paddy fields, mid-season drainage has potential to be an effective option to mitigate the net GWP from rice fields when rice residue is returned to the fields. However, there is the risk that N2O emission offsets reduction of CH4 emission or, moreover, brings higher GWP than CH4 emission when rice straw is not returned to the fields and when N fertilizer is applied at a high rate.

A common conclusion for all three crops is that it is necessary to generate more data sets where simultaneous measurements of CH4, N2O and CO2 emissions are collected together with C sequestration data to be able to better estimate the net GWP of wheat, maize and paddy fields.

Many agricultural mitigation activities show synergy with the goals of sustainabil-ity. Mitigation policies that encourage efficient use of fertilizers, maintain soil C and sustain agricultural production are likely to have the greatest synergy with sustainable development (Barker et al., 2007). However, the link between sustainability (conservation agriculture) and GHG emissions is a complex one and the balance between C sequestration, leaching losses and GHG emission needs to be carefully considered and analysed. This is an area in great need of additional research.

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