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N 2 O and NO emissions, the water usage and grain yields of a maize field in the North China Plain (NCP) under traditional flood irrigation, drip irrigation and drip fertigation were compared. With respect to the flood irrigation treatment, N 2 O emissions were reduced by 13.8% in the drip irrigation treatment and 7.7% in the drip fertigation treatment. NO emissions were reduced to 16.7% in the drip irrigation treatment but increased by 21.7% in the drip fertigation treatment. The molar ratios of NO/N 2 O within 2 days after each fertilization event were evidently greater from the drip fertigation treatment than from the flood irrigation treatment, indicating that nitrification was more intensive in the drip fertigation treatment than in the treatment of flood irrigation. Compared with the flood irrigation treatment, evident increase of the maize yields in the drip irrigation treatment (28%) and the drip fertigation treatment (3.7%) were found. Although the drip fertigation treatment could evidently increase NO emission, the 40% water reduction in drip fertigation is of great importance for the sustainable development of agriculture in the NCP where water resources are extremely limited. To mitigate NO emissions from agricultural fields in the NCP with drip fertigation, the addition of a nitrification inhibitor combined with N or nitrate fertilizer was recommended. [ABSTRACT FROM AUTHOR]

Agricultural soil has been recognized as a major source of atmospheric NO and N 2 O emissions which have important impacts on regional and global environments. Here we comparably investigated the effects of ammonium, nitrate fertilizers and nitrification inhibitor dicyandiamide (DCD) addition on NO and N 2 O emissions from the agricultural soil in the North China Plain (NCP). Compared with the ammonium fertilizer application, the reductions of NO emissions caused by nitrate fertilizer and DCD addition were 100% and 93%, and of N 2 O emissions were 54% and 74%, respectively. Remarkable reductions of NO and N 2 O emissions were also observed from five different agricultural soils in the NCP by replacing ammonium with nitrate fertilizer, indicating that nitrification is the predominant process for the emissions of NO and N 2 O from the soils in the vast area of NCP. NO emission peaks were found to be several days later than N 2 O peaks after the application of ammonium fertilizer and flooding irrigation, implying that most of NO initially produced via nitrification process might be fast reduced to N 2 O under the high soil moisture condition. Interestingly, the relative contribution of denitrification to N 2 O emission showed obviously time-dependent, e.g., evident N 2 O emission caused by the application of nitrate was only observed after the basal fertilization for the maize and the topdressing for the wheat. Replacing ammonium with nitrate fertilizer and mixing with the nitrification inhibitor are verified to be effective measures for mitigating NO and N 2 O emissions from arable soils in the NCP. [ABSTRACT FROM AUTHOR]