Characteristics of N2O and NOx Emissions from Purple Soil Under Different Fertilization Regimes

Abstract

N2O and NOx emissions from a winter wheat-summer maize rotation system in purple soil were measured on a long-term fertilization platform of purple soil for two consecutive cropping years (from November 2014 to September 2016) by using a closed-chamber and gas chromatography-based system. Chemical fertilizer (NPK), pig manure (OM), incorporation of crop residues plus synthetic NPK fertilizer (RSDNPK), pig manure plus synthetic NPK fertilizer (OMNPK), and nitrification inhibitor with NPK fertilizer (DCDNPK) under the same rate of total nitrogen were involved in monitoring N2O and NOx emissions. Short-term fertilizer-free treatment (CK) was used as a control for emission coefficient calculation. The results showed that N2O emission peaks appeared in the early stage of fertilization and in the period of heavy rainfall for all fertilization regimes. The NOx emission process was similar to that of N2O, in that emission peaks appeared at the early stage of fertilization, yet no obvious emission peaks were observed during heavy rainfall. The annual cumulative emissions of N2O from NPK, OM, RSDNPK, OMNPK, and DCDNPK were 1.35, 4.38, 1.43, 2.46, and 0.92 kg·hm-2, respectively, and the emission coefficients were 0.33%, 1.41%, 0.36% 0.73%, and 0.18%. The annual emissions of NOx from NPK, OM, RSDNPK, OMNPK, and DCDNPK were 0.11, 0.38, 0.10, 0.27, and 0.04 kg·hm-2, respectively, and the cumulative emission coefficients were 0.03%, 0.13%, 0.03%, 0.09%, and 0.01%. Amendment of organic material was the main stimulator for N2O and NOx emissions, as they significantly increased 226% and 262% (for OM) and 83% and 157% (for OMNPK), respectively (P<0.01), compared with conventional synthetic fertilizers. The application of synthetic fertilizers combined with nitrification inhibitor (DCDNPK) significantly reduced N2O emissions 32% and NOx emissions 62% (P<0.01), whereas straw returning with NPK application increased N2O emissions 6% and reduced NOx emissions 5% (P>0.05). Furthermore, statistical analyses showed that soil inorganic N content was the main regulating factor of N2O and NOx emissions together, whereas soil water-filled pore space (WFPS) and temperature were the respective main regulating factors of N2O and NOx emissions individually.