Nitrous oxide emissions in a winter wheat - summer maize double cropping system under different tillage and fertilizer management

An accurate estimation of nitrous oxide (N2O) emission from 110 million ha of upland in China is essential for the adoption of effective mitigation strategies. In this study, the effects of different tillage practices combined with nitrogen (N) fertilizer applications on N2O emission in soils were considered for a winter wheat (Triticum aestivum L.) - summer maize (Zea mays L.) double cropping system. Treatments included conventional tillage plus urea in split application (CTF1), conventional tillage with urea in a single application (CTF2), no-tillage with straw retained plus reduced urea in a split application (NTSF1) and no-tillage with manure plus reduced urea in a split application (NTMF1). The amounts of N input in each treatment were 285 and 225kg N/ha for wheat and maize, respectively. Both NTSF1 and NTMF1 were found to reduce chemical N fertilizer rates by 33.3% (wheat) and 20% (maize), respectively, compared to CTF1 and CTF2. N2O emissions varied between 3.2 (NTSF1) and 9.9 (CTF2) kg N2O-N/ha during the wheat season and between 7.6 (NTFS1) and 14.0 (NTMF1) kg N2O-N/ha during the maize season. The yield-based emission factors ranged from 21.9 (NTSF1) to 60.9 (CTF2) g N2O-N/kgN for wheat and 92.5 (NTSF1) to 157.4 (NTMF1) g N2O-N/kgN for maize. No significant effect of the treatments on crop yield was found. In addition to reducing production costs involved in land preparation, NTSF1 was shown to decrease chemical fertilizer input and mitigate N2O emissions while sustaining crop yield.