Nitrogen Nutrition Of Rice Research Articles

Sesbania Rostrata as alternative nutrient source for the rice crop .

This study evaluated the effect of using the green manure Sesbania rostrata as a preceding crop on the agricultural yield of rice. The rice was cultivated with two levels of mineral fertilizers (50 and 100% of the economical optimum level of N-P-K). Additionally, the contribution to the nitrogen nutrition of rice from the green manure previously incorporated into the soil was studied in pots using <sup>15</sup>N stable isotope analysis. The results indicated that the Sesbania rostrata incorporation allowed the paddy rice yield to increase by at least 1 Mg ha<sup>-1</sup> and to save 50% of the mineral fertilization employed, during two consecutive harvests. The <sup>15</sup>N isotope analysis showed that although the N accumulation by the crop was significantly stimulated, the green manure N did not contribute directly to the growth of the rice plants, at least during their first cycle. Nevertheless, it is expected that in the medium term, the organic N derived from this green manure would restore the soil mineralized N extracted by the rice crop, thereby balancing the N losses in the system and even improving the soil nitrogen fertility.

Impact of biochar application on nitrogen nutrition of rice, greenhouse-gas emissions and soil organic carbon dynamics in two paddy soils of China

Two field microcosm experiments and 15N labeling techniques were used to investigate the effects of biochar addition on rice N nutrition and GHG emissions in an Inceptisol and an Ultisol. Biochar N bioavailability and effect of biochar on fertilizer nitrogen-use efficiency (NUE) were studied by 15N-enriched wheat biochar (7.8803 atom% 15N) and fertilizer urea (5.0026 atom% 15N) (Experiment I). Corn biochar and corn stalks were applied at 12 Mg ha−1 to study their effects on GHG emissions (Experiment II). Biochar had no significant impact on rice production and less than 2 % of the biochar N was available to plants in the first season. Biochar addition increased soil C and N contents and decreased urea NUE. Seasonal cumulative CH4 emissions with biochar were similar to the controls, but significantly lower than the local practice of straw amendment. N2O emissions with biochar were similar to the control in the acidic Ultisol, but significantly higher in the slightly alkaline Inceptisol. Carbon-balance calculations found no major losses of biochar-C. Low bio-availability of biochar N did not make a significantly impact on rice production or N nutrition during the first year. Replacement of straw amendments with biochar could decrease CH4 emissions and increase SOC stocks.

Root-induced changes in radial oxygen loss, rhizosphere oxygen profile, and nitrification of two rice cultivars in Chinese red soil regions

Aims To evaluate the external and internal morphological differences of roots that might influence rice root radial oxygen loss (ROL) and the corresponding rhizosphere nitrification activity, growth characteristics and nitrogen nutrition of rice.

Influence of diazotrophic inoculations on nitrogen nutrition of rice

An experiment was conducted in microplots (7 by 7m) to investigate the effect of 2 non-symbiotic N2-fixing bacteria [Azotobacter (strain CS1) and Azospirillum (strain CM4)] in the presence of 50 kg N/ha on the performances of the diazotrophs with respect to nitrogen accretion and its transformation in the rhizosphere soils of rice (Oryza sativa L. cv. IR-36). In most cases, a successful inoculation of the diazotrophs was recorded, with the proliferation of Azotobacter and Azospirillum, either alone or in combination, in the rhizosphere soils, and nitrogenase activity (C2H2 reduction) of the microbes was present in rice roots. The uninoculated soil receiving 100 kg N/ha recorded the highest amount of total nitrogen, non-hydrolysable organic nitrogen, available nitrogen, and hydrolysable organic nitrogen content in the rhizosphere soils, resulting in greater yield of the crop. Inoculation of the diazotrophs substantially increased different fractions of nitrogen content in the rhizosphere soils, and the increase in total nitrogen, non-hydrolysable organic nitrogen, and hydrolysable organic nitrogen was greater due to Azotobacter than either Azospirillum or a combination of Azotobacter and Azospirillum. Total and mineral nitrogen content increased at maximum tillering to flowering stages of the crop, followed by a decline at maturity, whereas, hydrolysable organic nitrogen decreased with a concomitant increase in non-hydrolysable fraction with the age of the crop.

Mineralization of soil organic nitrogen under waterlogged conditions in relation to other properties of tropical rice soils

The mineralizable nitrogen pool in wetland rice soils plays a dominant role in the nitrogen nutrition of rice even in fertilized paddies. There is a lack of information on how different soil properties affect ammonification of organic nitrogen in wetland rice soils. Surface samples of 39 diverse Philippine soils representing a wide range of pH, organic matter and texture were studied to determine the relationships between ammonification of organic nitrogen and soil properties. Simple correlation analysis showed that ammonium production was correlated highly significantly with total nitrogen (r = 0.94**), organic carbon (r = 0.91**) and C/N ratio (r = -0.46**), but it was not significantly correlated with cation exchange capacity, clay or pH. Multiple regression analayses showed that organic matter (organic carbon and total nitrogen) accounted for most of the variation in mineralizable nitrogen. These results suggest that organic carbon content is a good index of mineralizable nitrogen in tropical wetland rice soils.

Secondary effects of potassium and nitrogen nutrition of rice: Change in microbial activity and iron reduction in the rhizosphere

In solution culture experiments with rice the effects of different potassium applications and of various nitrogen sources on some criteria of microbial activity were studied. The following results have been obtained: The number of bacteria in the rhizosphere depends on the form of nitrogen available to the plants and the potassium nutritional state. With ammonium as a nitrogen source a greater number of bacteria is found in the rhizosphere than with nitrate. The interruption of potassium nutrition results in an increase in the total number of bacteria. In accordance with the different bacterial colonisation, the oxygen content in the nutrient solution with nitrate remains higher than with ammonium nutrition. With an increase in bacterial number after K interruption, a corresponding depression of the oxygen content in the nutrient solution can be noted. This is due to the higher respiration rate of the roots and the bacteria adhering to them in K-deficient plants. K deficiency consequently results in an increased concentration of reduced divalent iron in the nutrient solution. From the above results it follows that optimum potassium nutrition makes an essential contribution towards counteracting highly reducing conditions in paddy soils.