Different responses of nitrous oxide emissions to liming and manure amendment of an acidic ultisol are controlled by autotrophic and heterotrophic nitrification.

Long-term lime and manure amendment can alleviate soil acidification, but their impacts on nitrous oxide (N 2 O) emissions and their production pathways remain largely unclear. Here, a 15N tracing study was conducted to explore the effect of lime and manure amendment on N 2 O production pathways and gross nitrogen (N) transformation rates of an acidic Ultisol. Soils were sampled from a 33-year field fertilization experiment, including three treatments of mineral NPK fertilizer (NPK), NPK plus lime (NPKL), and NPK plus manure (NPKM). Compared to NPK, N 2 O emissions increased by 25.2% for NPKL but decreased by 22.1% for NPKM, indicating that different pH-raising substances may have different effects on N 2 O emissions. The 15N tracing analysis indicated that heterotrophic nitrification-derived N 2 O played a dominant role in N 2 O emissions while NPKL significantly increased autotrophic nitrification-derived N 2 O production. The increased relative contribution of autotrophic nitrification to N 2 O emissions by NPKL resulted in an increase of N 2 O emissions in the acidic Ultisol. In contrast, NPKM decreased heterotrophic nitrification and autotrophic nitrification-derived N 2 O production, leading to a decrease of N 2 O emissions. Our results show that lime and manure amendment can have different impacts on N 2 O emissions due to their differential effects on autotrophic and heterotrophic nitrification, providing important insights for the sustainable management of acidic arable soils. • Liming increased N 2 O emissions while manure amendment decreased N 2 O emissions. • Heterotrophic nitrification played a dominant role in N 2 O emissions from acidic Ultisols. • Liming increased N 2 O emissions through increasing autotrophic nitrification. • Manure amendment reduced N 2 O emissions by suppressing heterotrophic nitrification. [ABSTRACT FROM AUTHOR]