Management of rice production systems to increase productivity

analyzed by determining of genotypic variation in water uptake and how the
water is used in the processes that lead to formation of grain yield (Fukai and
Cooper, 1995). Once genotypic variation in resource capture or utilization
efficiency (yield produced per unit nutrient uptake) is found, then
physiological or morphological factors that are responsible for such variation
can be further examined.
Of the major determining factors of phenology, at least two can be
ruled out in the tropics. Low temperature during the growing season of
upland rice, and photoperiodism. However, drought is clearly a major
limiting factor, especially drought that develops during panicle development
which delays flowering of rice in upland conditions (Inthapan and Fukai,
1988; Fukai, 1999). Under upland field conditions, Lilley and Fukai (1994)
showed that the magnitude of delay in flowering was associated with the
severity of drought conditions. Development of the panicle is very sensitive to
soil water availability, and the rate of development is reduced by a small
water deficit and ceases completely with the occurrence of severe drought.
Drought is thus a major problem for upland rice. Yield loss due to
drought in upland rice was estimated at 60% in the 2002 growing season in
The Gambia when rainfall declined by 40% from the 10‐year normal average
of 760 mm. In fact, earlier results with upland rice production in The Gambia
showed that upland rice grown under 700 mm to 1,000 mm rainfall may be
subjected to moisture stress at any stage of crop growth due to periodic
drought spells and uneven distribution. Drought‐related problems of crop
establishment occur in many of the world’s rainfed rice growing areas
(O’Toole, 1981). Drought affects plant growth primarily because of the
shortage of water in the plant. Water is essential for plant growth, and
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