Central Rice Research Institute Annual report...2011-12

Natural Resource Management and Input Use Efficiency for Improved Crop
Fig. 19. Performance of aerobic rice (Apo) under varied
moisture regimes
reverse trend was observed with IW/CPE ratio from
0.8 to 1.2.The sterility percentage of spikelets almost
doubled with increase in IW depth from 25 to 75 mm
but decreased with increase in IW/CPE ratio.
Transformation and availability of N in
aerobic rice soils under different Nitrogen
management strategies
A field trial was conducted in dry season during
2011 with aerobic rice variety Apo under
different N management practices
viz., control, LCC based N application
(30 kg Nha -1 at 20 days after sowing
(DAS), 45 kg N ha -1 between 30-50 DAS
as and when LCC reading < 4.0, 15 kg
Nha -1 between 50-80 DAS as and when
LCC reading < 4.0), SPAD meter based
N application 30 kg N ha -1 at 20 days
after sowing (DAS), 45 kg N ha -1 between
30-50 DAS as and when SPAD
reading < 35.0, 15 kg N ha -1 between
50-80 DAS as and when SPAD reading
< 35.0), Recommended dose (60 kg
N ha -1 at sowing, 30 kg N ha -1 at maximum
tillering, 30 kg N ha -1 at panicle
initiation). Results revealed that use
of LCC and SPAD could ensure equal
level of yield as that of recommended
dose with 25 % less fertilizer application.
Both LCC based and SPAD meter
based recommendation resulted higher agronomic
N use efficiency (17-18%) and N recovery
efficiency (26-30 %) over the recommended
dose (Fig. 20).
Transformation and availability of Zn
under aerobic rice system
A laboratory incubation experiment was
carried out to study the transformation of applied
zinc in paddy soil under aerobic and
submergence moisture regimes with three
sources of Zn applications viz., control (no
Zn applied), Zinc Sulphate (5 kg Zn ha -1 ) and
Zinc Oxide (5 kg Zn ha -1 ). The study on transformation
of added zinc indicated that all the
zinc fractions except crystalline sesquioxide
and residual zinc fractions showed an increased
trend with zinc application at aerobic
and submergence moisture regimes during
the incubation period. The days of incubation
had significant effect on different zinc fractions
under aerobic and submergence moisture regime at 15,
30, 60 and 120 days after incubation. With increasing
incubation period, water soluble plus exchangeable
zinc, organically bound zinc, crystalline sesquioxide
bound zinc and available zinc fraction decreased in
both the moisture regimes. The magnitude of decrease
was more in submergence moisture regimes. Manganese
oxide bound zinc, amorphous sesquioxide zinc
and residual zinc showed an increasing trend with increasing
incubation period. The water soluble plus exchangeable
zinc, organically bound zinc and crystal-
Fig. 20. Agronomic N use efficiency (AE N
) and N recovery efficiency
(RE N
) under different N application strategy in aerobic condition
CRRI ANNUAL REPORT 2011-12
63