Questions on background N2O emissions?

Despite substantial contribution (10–52%) of BNE to the overall N₂O emissions in agricultural lands (Li et al. 2001; Brown et al. 2002; Sozanska et al. 2002; Yan et al. 2003; Lu et al. 2006; Gu et al. 2009; van Beek et al., 2011), current understanding of BNE has remained at a low level and this causes conflicting interpretation and application of IPCC guideline (IPCC, 2006) for agricultural N₂O inventories (de Klein et al., 2010). To improve the methodology for N₂O inventory and accuracy of N₂O emissions estimation, the following key questions should be urgently addressed: What are the sources of BNE? Is BNEA significantly different from BNEN? Is BNE significantly different by land-use type (i.e., crop lands, pasture, paddy fields) or ecosystem type (i.e., tropical forest, temperate forest, savannah)?  What are the key processes or key controlling factors for BNE?