Nitrous oxide emission following Urea-N fertilization of Wetland rice

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Abstract
The emission of nitrous oxide from a flooded rice field subjected to different urea-N fertilization rates and metbods of application was measured duriog 1980 on Crowley silt loam soil (Typic Albaqualfs). Measurements were made regularly throughout the growing season using diffusion chambers. The application of urea-N led to an increase in nitrous oxide evolution; however, the emissions from the fertilized soil in 105 days were low, ranging from 90 to 171 g N ha-1. Nitrous oxide emission was found to be correlated with the exchangeable NH4 ++-N content of the soil and the NO2 -NO3 --N concentration of the floodwater. The corresponding emission from the unfertilized soil averaged 74 g N ha-1. The apparent fertilizer N recovery in the aboveground portion of the plant ranged from 43 to 71%; however, the fertilizer induced emissions of nitrous oxide represented only 0.01 to 0.05% of the urea-N applied. In general, plant recovery was lower when the fertilizer was applied in two top-dressings.