抄録
Water management is important for sustainable rice production and productivity to meet increasing demand for food and household income. This study examined how underground water tables affect the yield and yield components of upland rice NERICA 4. We conducted an experiment in which the rice plants were grown under upland conditions with two factors: Irrigation (3 and 5 mm/day) and underground water level (35 cm, 45 cm, 55 cm deep, and no groundwater). The presence of groundwater had a profound impact on the yield: It increased from 0.2 and 2.1 t/ha without groundwater to 6.3 and 6.7 t/ha with groundwater at 35 cm deep for 3 and 5mm/day irrigations, respectively. Yield components that led to these yield increases were sharply different between the two irrigation treatments. The most contributing component was the number of spikelets/m2 for 3 mm/day, whereas it was the %-grain-filling for 5 mm/day. The drought tolerance-recovery ability of NERICA 4 contributed to this difference: Under drought conditions, its root system developed faster, longer, denser, and deeper than under optimal water conditions, so that the roots of plants under 3 mm/day irrigation reached the 35 cm-deep groundwater table before the panicle initiation stage, earlier than in other treatments. Under 5 mm/day irrigation, optimal water application and capillary water from the groundwater zone induced a strong trade-off between the number of panicles/m2 and the number of spikelets/panicle. These findings based on the two-factor experiment were confirmed in terms of the soil water potential of each plot.
