Quantifying Nitric Oxide Emissions Under Rice-Wheat Cropping System.

More than 50% of applied N is not utilized by crops, posing huge economical costs and environmental concerns. Therefore, N management research has focused on increasing use efficiency and crop productivity and reducing nitrous oxide (N₂O) and nitric oxide (NO) emissions. Enhanced-efficiency fertilizers (EEF), such as those containing nitrification inhibitors and urease inhibitors, and slow-release fertilizers have been developed to increase the efficiency of fertilizer use by crops.  Similarly, enhanced-efficiency fertilizer application (EEFA) method such as urea deep placement (UDP) reduces N losses up to 35% and increases rice yield up to 20% compared to conventional broadcast application. EEF and EEFA are also effective for mitigating N₂O and NO emissions. NO is an environment pollutant that participates in photochemical reactions in the troposphere that produces ozone. NO also contributes to the formation of fine particles (PM). Both of these are associated with adverse health. Studies on the effects of EEF and EEFA on NO emissions are lacking, particularly in flooded rice fields and in rice-based cropping systems where soils alternate between anaerobic and aerobic conditions.  Limited interest in NO research may also be attributed ot the fact that much of NO emission results from non-agricultural sectors. NO results for flooded rice followed by wheat is presented for treatments comprising EEFA, conventional N application, and alternate-wetting and drying. Overall NO emission factor for flooded rice ranged from -0.006-0.02% compared with 0.02-0.15% for wheat.