Quantifying nitric oxide emissions under rice-wheat cropping systems

• Published in: Environmental pollution (1987) Vol. 250; pp. 856 - 862
• Main Authors: Gaihre, Yam Kanta, Bible, Wendie D., Singh, Upendra, Sanabria, Joaquin
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2019
• Subjects: Fertilizer deep placement; Nitric oxide emissions; Nitrogen use efficiency; Rice-wheat system; Nitric oxide emissions; Fertilizer deep placement; Nitrogen use efficiency; Rice-wheat system
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2019.04.121

Urea deep placement (UDP) increases nitrogen use efficiency (NUE) and crop yields while reducing nitrogen (N) losses to the environment. However, studies on its environmental impacts on nitric oxide (NO) emissions are still limited. Therefore, we conducted a greenhouse experiment to quantify the NO emissions from a rice-wheat system. NO emissions were measured from three N fertilizer treatments – control (no N), UDP, and broadcast prilled urea (PU) – using an automated gas sampling and analysis system continuously for a rice-wheat cropping cycle. In rice, UDP was tested under two water regimes – continuous flooding (CF) and alternate wetting and drying (AWD). Fertilizer treatments had significant effects (p < 0.05) on NO emissions. UDP with AWD irrigation increased NO emissions (3.41 g N ha−1) (p < 0.05) by 2.5-times compared to UDP with CF (1.35 g N ha−1). But emissions were similar between UDP and broadcast PU under the CF water regime. In wheat, the application of N fertilizer – regardless of application methods – increased NO emissions (615 g N ha−1, average across application methods) by 10-times over control (62.52 g N ha−1). However, emissions were not significantly (P > 0.05) different among the treatments. Fertilizer induced emission factors (EFs) were not affected by N placement methods in either rice or wheat. On average, EFs in the rice were very low (<0.002%) compared to the wheat (0.5%). This study reveals that (regardless of treatments), the contribution of rice (<4 g N ha−1) on total annual NO emissions (433 g N ha−1) was very small (<0.5%) compared to emissions from wheat. [Display omitted] •Nitric oxide (NO) emissions were measured from rice-wheat cropping systems using automated system.•NO emissions were compared between two nitrogen placement methods.•Effects of urea deep placement (UDP) on NO emissions varied with water regimes.•Alternate wetting and drying (AWD) irrigation in rice increased NO emissions. Contribution of rice cultivation on annual nitric oxide emissions is negligible compared to wheat, and N fertilizer placement in wheat had no significant effects on emissions.