Quantitative evaluation of differences in cultivar and fertilization to drought resistance of rice by stomata and soil water changes

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The objective of this study is to evaluate the effects of water stress on the growth of rice by the measurements of stomata and soil water, and to clarify the differences in cultivar and fertilization to drought resistance quantitatively. Rice was grown in field under vinyl house and water stress was given with suspending irrigation. Besides Asian rice, NERICA (New Rice for Africa) lines were tested. Stomatal conductance, soil water content of each depth, top dry weight and root characteristics were measured and relationships between them were compared. There were large differences in dry weight and yield among NERICA lines, some showed higher growth than drought resistant Asian rice cultivars. Cultivars and lines with high growth showed high stomatal conductance. There was negative correlation between soil water content and dry weight in Asian rice cultivars, and in cultivars that showed high growth water absorption was high. In NERICA lines on the contrary there was no correlation between them, and it seems that there is large difference in water use efficiency among NERICA lines and that some lines with low water absorption show high growth by high water use efficiency. In Asian rice cultivars there was correlation between dry matter production and root characteristics, but in NERICA lines there was no correlation between them. Drought resistant cultivars in Asian rice showed high growth by absorbing much water. In NERICA lines on the contrary variation in water use efficiency is large and some seem to show high growth with small water absorption, and they seem to be appropriate for the long term cultivation in dry region. By adding compost in low fertilizer level, water stress was reduced and dry matter production was maintained high.