Simultaneous quantification of N 2 , NH 3 and N 2 O emissions from a flooded paddy field under different N fertilization regimes

Abstract

Gaseous nitrogen (N) emissions, especially emissions of dinitrogen (N 2 ) and ammonia (NH 3 ), have long been considered as the major pathways of N loss from flooded rice paddies. However, no studies have simultaneously evaluated the overall response of gaseous N losses to improved N fertilization practices due to the difficulties to directly measure N 2 emissions from paddy soils. We simultaneously quantified emissions of N 2 (using membrane inlet mass spectrometry), NH 3 and nitrous oxide (N 2 O) from a flooded paddy field in southern China over an entire rice‐growing season. Our field experiment included three treatments: a control treatment (no N addition) and two N fertilizer (220 kg N/ha) application methods, the traditional surface application of N fertilizer and the incorporation of N fertilizer into the soil. Our results show that over the rice‐growing season, the cumulative gaseous N losses from the surface application treatment accounted for 13.5% (N 2 ), 19.1% (NH 3 ), 0.2% (N 2 O) and 32.8% (total gaseous N loss) of the applied N fertilizer. Compared with the surface application treatment, the incorporation of N fertilizer into the soil decreased the emissions of NH 3 , N 2 and N 2 O by 14.2%, 13.3% and 42.5%, respectively. Overall, the incorporation of N fertilizer into the soil significantly reduced the total gaseous N loss by 13.8%, improved the fertilizer N use efficiency by 14.4%, increased the rice yield by 13.9% and reduced the gaseous N loss intensity (gaseous N loss/rice yield) by 24.3%. Our results indicate that the incorporation of N fertilizer into the soil is an effective agricultural management practice in ensuring food security and environmental sustainability in flooded paddy ecosystems.

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