Management of rice production systems to increase productivity

management practices (dry land/irrigated systems, sowing/planting density,
pest and diseases and weed control) and source, time and method of
application of fertilizer materials. Input‐output curves are situation‐specific.
Differences in response curves from one situation to another may be a
consequence of differences in uptake of the nutrient by the crop, and
management practice, or both (Black, 1993).
It is however possible to develop cultivars that use the limited water
more effectively, either directly through improvement in
photosynthesis/transpiration ratio or indirectly through mechanisms such as
more extraction of the limited water available in the soil (Pantuwan et al.,
1997.)
Drought is not a stable phenomenon, and soil water availability
changes over time within a season. It often starts as mild stress and then may
become severe with time, possibly lasting for a long period. In some cases,
drought develops early during the vegetative stage, while in others it
develops later, toward crop maturity (Fukai, 1999). Drought occurring at
different growth stages has different effects on rice yield. Boonjung and Fukai
1996 reported that drought that develops just prior to flowering affects yield
more severely.
The drought patterns differ among locations and among years.
Cultivars adapted to one type of drought are not necessarily resistant to other
types of drought. Identification of common drought patterns and their
likelihood of occurrence are important for development of cultivars that are
suitable to a specific region (Fukai, 1999). In the Gambia, drought at the time
of crop germination (just after planting) and late‐season drought (terminal
drought) are often the most critical. In order to avoid these drought stages,
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