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

Abstract

Long-term lime and manure amendment can alleviate soil acidification, but their impacts on nitrous oxide (N2O) 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 N2O 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, N2O 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 N2O emissions. The 15N tracing analysis indicated that heterotrophic nitrification-derived N2O played a dominant role in N2O emissions while NPKL significantly increased autotrophic nitrification-derived N2O production. The increased relative contribution of autotrophic nitrification to N2O emissions by NPKL resulted in an increase of N2O emissions in the acidic Ultisol. In contrast, NPKM decreased heterotrophic nitrification and autotrophic nitrification-derived N2O production, leading to a decrease of N2O emissions. Our results show that lime and manure amendment can have different impacts on N2O emissions due to their differential effects on autotrophic and heterotrophic nitrification, providing important insights for the sustainable management of acidic arable soils.