Management of rice production systems to increase productivity

very dry year a low N uptake at maximum tillering is predictable, resulting in
lesser N available for grain production. The N use efficiency was considerably
affected by the amount of precipitation during the cropping season. In 2002,
the severe drought condition that prevailed caused a significant reduction in
the N use efficiency for grain production at all levels of nutrient application
except the high‐input level. Yield loss at the very high input rate was as a
result of blast (Figure 9). In 2000, which was a drought free year, NUEg was
relatively highest at the low‐input level of fertilizer application, but in drier
years the point of high NUEg was at the high‐input level. The low‐input
variety WAB56‐50 had the highest NUEg at all levels of fertilizer input in 2000
and 2001. In the driest year WAB377‐B‐16‐L3 had the best NUEg at high‐input
fertilizer application level. There are genotypic differences in NUEg, and the
level apparently depends on amount of available nutrient and moisture. Very
low NUEg and relative high N stem content were recorded in 2002 at the zero
and low‐input application levels. This may be explained by the fact there may
have been reduced translocation due to reduced mass flow in the plant. This
caused N stagnation in the stem and less translocation for use in grain
production. It is estimated that 70% of the plantʹs needs at grain‐filling stage
comes from remobilization from within the plant.
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