Management of rice production systems to increase productivity

for grain production after panicle initiation. The level of N in plant tissue at
maximum tillering stage was found to be higher than at harvest. However, in
the drought year (2002, with 590 mm rainfall), N‐levels in plant tissue at
harvest remain high, as result of which, probably, grain yield was lowered.
The results suggest that low‐input varieties have better potential to
capture and utilize N. High yield potential in the low‐input varieties is due to
increased biomass production rather than HI. The massive biomass produced
in the low‐input varieties during the vegetative phase is a huge sink for N.
After flowering, translocation of N from the vegetative organs to the grain
becomes active. There is also some translocation of carbohydrates from the
vegetative plant parts to the grains after flowering, a large portion of which
goes into grain.
Increased biomass production in low‐input varieties provided them
with an ability to outgrow and suppress weed development by shading them.
Weed infestation was less than 50% in plots with Low‐Input varieties than in
those with the conventional variety. Early canopy closure is also cited in some
work as having the potential to reduce NH3 volatilization.
The NuMaSS predictions were more realistic in the drier year (590 mm)
than when it was wetter (970 mm) probably because of N loss by leaching
during the wetter year. The NuMaSS default NUE of 50% may be too high
during the wetter year as a result of higher leaching and run‐off than normal
years, but it was more appropriate for the drier years. In the normal year,
NUE was about 35%. Given these efficiencies for different rainfalls, split
application of N is highly recommended. A low‐input level of fertilizer
application (40‐40‐40 kg/ha NPK) may be budgeted for at the beginning of the
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