The assessment of nitrogen balance under flooding and saturation circumstances using N-15

The use15 N- balance techniques has already identified N-loss as a major problem in lowland rice management. Ammonium sulphate labelled with 5% N-15 atom ex. as a basal fertilized through special column in order to study the effect of flooding and saturation condition on the potential loss of nitrogen fertilizer. Rice straw at a rate of 1% was incorporated with the soil in order to study the role of rice straw (as a source of organic matter) on N-loss. Results show that the application of rice straw under flooding condition resulted in an increase of the biomass. It was observed that flooding circumstances may reduce the loss of nitrogen. Since N-recovery under flood and saturation rhizosphere (with plant) conditions were about 75% and 56%, respectively. The effect of rice root (rhizosphere) on nitrification has been observed. Results of flood and non flood rhizossphere show that the nitrogen recovery were about 75% and 86%, respectively. Results show an indirect evidence that the process of rhizosphere nitrification denitrification resulted in a significant amount of N-loss.It is evident that deep placement and flooded condition proved to be an effective means of reducing the potential of N-loss. 1 fig., 3 tabs