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Data
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Former Fellows
Dissertation Abstracts
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Philippines |
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| Name |
Ernesto Guttierez CASTILLO |
| Position |
Assistant Scientist 1
Crop, Soil and Water Sciences Division, The International Rice Research Institute |
| Japanese Advisor |
Kazuyuki INUBUSHI
Professor,Chiba University |
| Nutrient-use efficiency of rainfed lowland rice as affected by salinity and water stresses |
Salinity and water stress represent two of the most important environmental stress influencing the productivity of agricultural systems worldwide. Therefore increasing nutrient availability and plant resistance to drought and salinity is important for increasing rice yield. Split fertilizer N application, the use of controlled release fertilizers and the adoption of dry seeded rice technology can be alternatives to increase the productivity of drought prone rainfed lowland rice environments. Similarly in saline environment, separating osmotic and ionic stress is an important step in understanding the basis of tolerance and in designing effective breeding strategies to develop tolerant genotypes.
Series of field and pot experiments were conducted to determine the effects of water deficit and salinity on critical growth stages of rice. The water stress experiments showed that water stress at flowering is most detrimental to yield, followed by stress at panicle initiation, while stress at the vegetative stage does not affect grain yield. Dry seeded rice was shown to be more resistant to water stress more than other crop establishment methods. The controlled release fertilizers did not offer any advantage over urea split applications because of its availability and cost, therefore multiple-split applications of urea remain a better option for farmers to use in rainfed lowland areas.
 Salinity stresses at different rice growth stages was dependent on level and timing of salinity stress. Grain yield reductions caused by medium and high osmotic stresses were significantly higher when stress was imposed during the reproductive stage than in the vegetative stage. However, the lack of significant differences in phenology, biomass accumulation, and yield between the PEG and NaCl sources of stress suggested that the ionic stress effects were small and that the observed responses of IR64 to salinity in this study were mainly due to osmotic stress. Some rice cultivars are known for their tissue tolerance of a high concentration of Na+and this could partially explain the lack of response to high levels of tissue Na+.
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Asian Program