Effect of Rice Planting on Nitrous Oxide (N₂O) Emission under Different Levels of Nitrogen Fertilization

• Main Authors: Gil Won Kim, Pil Joo Kim, Muhammad Israr Khan, Sung-Jae Lee
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Agronomy
• Subjects: static chamber method; nitrogen fertilization; N₂O emission; rice paddy
• Online Access: https://www.mdpi.com/2073-4395/11/2/217

Nitrogen (N) fertilization is one of the most effective practices to increase productivity, and has therefore had a fast global increase. Consequently, the effects of the application of N fertilizer on emissions of N₂O have been widely studied, but the effect of rice planting on N₂O emission was not adequately quantified. To evaluate the effect of rice cultivation on N₂O emissions, different levels of N were applied in a typical temperate rice field, and the N₂O fluxes were compared in rice-planted and non-planted soils. Seasonal N₂O fluxes responded differently with respect to N fertilization in the two different soil conditions. In non-planted soils, seasonal N₂O fluxes ranged within 0.31–0.34 kg N₂O ha⁻¹ under 0 kg N ha⁻¹ fertilization, and significantly increased by increasing N fertilization rates, with an average rate of 0.0024 kg N₂O kg⁻¹ N for 3 years. In rice-planted soils, seasonal N₂O fluxes were also increased by N fertilization but showed large negative N₂O fluxes, irrespective of the N fertilization level. This study confirms that the rice reacted as a reducer of N₂O emissions, not an emission source, in paddy fields, suggesting that N₂O fluxes should be estimated by the static chamber planted with rice to obtain a more precise field environment. The differences of N₂O fluxes between the rice-planted and non-planted soils might have been caused by the rice plant’s rhizospheric activities, which may have influenced the N₂O consumption potential in the rice plants’ rhizosphere. The N₂O consumption potential was significantly increased with increasing N fertilization rates and was highly correlated with rice biomass yields. Therefore, the decrease in N₂O fluxes by N fertilization in rice-planted soils might have been caused by a decreasing denitrification potential in paddy soils.