Studies On Gaseous Nitrogen Losses From Rice Plant Tissue And The Mechanisms

The poor fertilizer-nitrogen use efficiency (FNUE) is a critical issue in irrigated rice system in China. The mass N losses and low nitrogen use efficiency (NUE) of rice production system has become a threat to the environment. Idea and practical approaches to improve NUE and avoid nitrogen destruction of natural ecosystems are considered to use high NUE rice varieties. Gaseous nitrogen losses from rice Plant tissue may be closely related to nitrogen efficiency. This study in 2006-2008 with different nitrogen efficiency in rice genotypes, use solution culture and field experiments to compare volatile form of gaseous nitrogen, the number of the major forms from different rice genotypes and gaseous volatile (NH3) release mechanism. The results are as follows:(1)There major types, NH3, N2O and NO2 could be checked and measured that volatilized from the rice shoot. The total amount of ammonia volatilization was much higher than that of N2O and NO2 volatilization. Ammonia was the main types of rice shoot nitrogen losses and the ammonia volatilization was the main path of rice shoot nitrogen losses.(2) Differences in ammonia volatilization rate were observed among of different genotypes. At different growth stages, the rate of NH3 volatilization was different. Ammonia volatilization from shoot of different genotypes rice increased with increasing applied nitrogen content.(3) N2O and N2O volatilization rate from nitrogen efficiency of different rice genotypes changed with the reproductive process. The amount of N2O and NO2 volatilization from rice canopy was the highest at booting stage and then became lower as the growth processes. At milking and matured stage the amount of N2O and NO2 volatilization was the lowest. There was significant genotypic variation in the amount of N2O and NO2 volatilization under two N levels. The amount of N2O and NO2 volatilizated of most from rice genotypes canopy increased as N rates increased.(4) There was relationship between Photorespiration and ammonia volatilization rate from rice. At same nitrogen level, Photorespiratory rate was positive with ammonia volatilization rate. More Photorespiratory rate more Glycolate oxidase activity. Compared with the untreated/control, spray of photorespiration inhibitor (INH) significantly decreased the NH3 volatilization rate for both varieties.(5) Glutamine synthetase activity and NH3 volatilization rate was a negative correlation. NH3 volatilization showed the opposite trend correspondingly. The amount of NH3 volatilized from rice canopy was significantly increased after the spray of GS inhibitor (MSO).(6) Difference in NH3 volatilization, total nitrogen accumulation, nitrogen dry matter production efficiency, nitrogen grain production efficiency, nitrogen harvest index, nitrogen agronomical use efficiency, nitrogen partial factor production and nitrogen physiological efficiency were significant under the same nitrogen level. NH3 volatilization,Total nitrogen accumulation, nitrogen dry matter production efficiency, nitrogen grain production efficiency, nitrogen harvest index, nitrogen agronomical use efficiency, nitrogen partial factor production and nitrogen physiological efficiency of nitrogen use efficiency decreased with adding nitrogen level.(7) Correlation analysis denote, there were significantly negative relationship between NH3 volatilization losses and total nitrogen accumulation, nitrogen dry matter production efficiency, nitrogen grain production efficiency and nitrogen harvest index under same nitrogen level. There were significant positive correlation between nitrogen losses and nitrogen accumulation; significantly negative correlationship between nitrogen losses and nitrogen dry matter production efficiency, nitrogen grain production efficiency and nitrogen harvest index.