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Experiments were conducted to study the dynamics of nitrous oxide (N₂O) emission from wheat varieties viz., Sonalika, HUW 468, HUW 234 and DBW 14 grown in alluvial soils of North Bank Plain Agroclimatic Zone of Assam, India. Attempts were made to find out the relationship of N₂O emission with plant morphophysiological, anatomical and soil properties. N₂O fluxes from wheat varieties ranged from 40 μg N₂O-N m⁻² h⁻¹ to 295 μg N₂O-N m⁻² h⁻¹. Soil organic carbon and soil temperature have shown significant relationship with N₂O flux. The rate of leaf transpiration recorded from the wheat varieties at different growth stages exhibited a positive correlation with N₂O emission suggesting that movement of N₂O along with the transpirational water flow may be an important mechanism of N₂O transport and emission through wheat plants. Anatomical investigation by scanning electron microscope revealed that N₂O emission has relationship with stomatal frequency of leaf and leaf sheaths. Variety HUW 234 with the highest stomatal frequency of leaf and leaf sheath also recorded higher seasonal N₂O emission compared to other varieties. Seasonal N₂O emission (E(sif)) of the varieties ranged from 3.25 to 3.81 kg N₂O-N ha⁻¹. Significant variations in E(sif) values were recorded within the varieties.

We investigated nitrous oxide (N2O) emission from an irrigated rice field over two years to evaluate the management of nitrogenous fertiliser and its effect on reducing emissions. Four forms of nitrogenous fertilisers: NPK at the recommended application rate, starch-urea matrix ( SUM) + PK, neem-coated urea + PK and urea alone (urea without coating) were used. Gas samples were collected from the field at weekly intervals with the static chamber technique. N2O emissions from different treatments ranged from 11.58 to 215.81 N2O-N μg/m2/h, and seasonal N2O emissions from 2.83 to 3.89 kg N2O-N/ha. Compared with other fertilisers, N2O emissions were greatest after the application of the conventional NPK fertiliser. Moreover, SUM + PK reduced total N2O emissions by 22.33% ( P < 0.05) compared with NPK during the rice-growing period ( P < 0.05). The results indicate a strong correlation between N2O emissions and soil organic carbon, nitrate, ammonium, above- and below-ground plant biomass and photosynthesis ( P < 0.05). The application of SUM + PK in rice fields is suitable as a means of reducing N2O emissions without affecting grain production. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is a major greenhouse gas contributing to global warming. Rainfed rice fields are considered to be a notable source of atmospheric N2O emission. To investigate the dynamics of N2O emission and the relationship of plant and soil properties with emission of N2O in rice, a field experiment was conducted. The five popularly grown rice varieties Luit, Disang, Kapilli, Siana and Phorma were grown in the fall season under rainfed conditions. N2O emission was measured at seven-day intervals starting from the day of transplanting for the whole crop growing season. We also measured soil parameters, e.g. soil pH, soil temperature, soil organic carbon, soil NO- 3 -N, and field water level; and plant growth parameters: root-shoot dry weight, root length and leaf area. Our results show that N2O emission from the plant varieties ranged from 1.24 μg to 379.40 μg N2O-N m-2 h-1. Seasonal N2O emission from the rice varieties ranged from 77 to 150 mg N2O-N m-2. Root dry weight, shoot dry weight, soil NO-3 -N, root length, leaf area and field water showed relationships with N2O emission. Root and shoot weight, soil NO-3 -N and field water were found to be the main factors influencing N2O emission. The varieties Phorma and Siana, with lower grain productivity but profuse vegetative growth, showed higher seasonal N2O emission. [ABSTRACT FROM AUTHOR]