CONTENTS

RESPONSE OF AEROBIC RICE TO IRRIGATION SCHEDULING AND NITROGEN
given as and when required to maintain the soil in
saturation condition throughout the crop growth
period. The amount of water given every time was
measured and summed up. The drip system was
established keeping 60 cm between two lateral lines
to accommodate aerobic rice. One lateral line is lied
between two crop rows. Distance between two
drippers is 50 cm. The discharge rate of drippers is 4
Lph. The diameter of lateral in-line was 16 mm. The
system was operated under a pressure of 1.2-1.5
kg/cm 2 . The source of irrigation water is open well
fitted with 3 H.P. electrical motor. Quantity of water
applied was measured treatment wise with water
meter fixed to the system. Amount of water applied
in I 1
was 220 mm, I 2
: 330 mm and I 3
: 450 mm (9
irrigations each at 50 mm depth). To control the
weeds, pendimethalin @ 1.2 kg a.i. ha -1 was applied
at 24 hours after sowing fb post-emergence
application of pyrazosulfuron ethyl @ 30 g a.i. ha -1 at
25 DAS in rice. They were sprayed using 500 litres
of water ha -1 with flood jet nozzle. A range of mean
minimum temperature of 23.4 to 24.6 0 C and mean
maximum temperature of 29.2 to 34.6 0 C was
recorded during the crop growth period. A total rainfall
of 827 mm was received during the crop season in
46 rainy days. The crop was harvested on 27 th
October, 2010. Pre and post-harvest observations in
respect of both growth and yield parameters were
recorded following standard procedures. Net returns
(Rs. ha .1 ) were calculated by deducting the cost of
cultivation (Rs. ha .1 ) from the gross returns (Rs. ha .1 )
excluding the cost incurred towards installation of
drip system. Nitrogen uptake (kg ha -1 ) was calculated
by considering nitrogen content (%) in grain / straw
at harvest. The other recommended cultural and pest
management practices were adopted.
Application rate of
drip system (mm/hr) = Lph (litres per hour) /
Distance between laterals x
Distance between dippers
= 4 Lph / 0.6 m x 0.5 m
= 13.33 mm/hr
Maintenance of soil under saturated condition
throughout the crop growth period resulted in
significantly taller plants (Table 1) compared to
scheduling irrigation at 100 or 150 % PE. Similarly,
significant number of tillers was recorded with soil
saturation over the other two schedules both at 30
and 60 days after sowing (DAS). In comparision,
scheduling irrigation at 150% PE was found to be
superior to 100% PE with respect to plant height and
tillers/m 2 . Among the nitrogen doses, application of
180 kg N ha -1 resulted in taller plants over 150 kg N
ha -1 which in-turn was significant over 120 kg N ha -1 .
The tiller number/m 2 was also significantly enhanced
with increase in N application i.e., from 120 to 180
kg N ha -1 both at 30 and 60 DAS.
The number of panicles/m 2 was significantly
higher with soil saturation compared to 100 % PE
but at par with 150 % PE (Table 2). The proportion
of unproductive tillers to total number of tillers tend
to increase at 100% PE compared 150% PE or soil
saturation both of which were at par with each other.
Maintenance of soil at saturation significantly
increased the number of filled grains / panicle with
corresponding decreases in chaffyness over 150 %
PE or 100 % PE. In-turn 150% PE differed
significantly with 100 % PE with higher number of
filled grains / panicle but reduced chaffyness.
Significantly longer panicles were recorded with soil
saturation compared to 100 % PE but at par with 150
% PE. However, the 1000- grain weight (g) did not
differ significantly among the different irrigation
schedules. The above results on plant growth and
yield attributes were in accordance with Maheswari
et al. (2007); Ghosh et al. (2012); Mahajan et al.
(2012) and Sridharan and Vijayalakshmi (2012).
Increased dose of N i.e., 180 kg N ha -1 resulted in
higher number of panicles over 120 kg N ha -1 but at
par with 150 kg N ha -1 . Contribution of unproductive
tillers gradually reduced with increase in N dose from
120 to 180 kg N ha -1 . There was a consistent and
significant increase in the number of filled grains /
panicle from 120 to 150 kg N ha -1 and then to 180 kg
N ha -1 . Chaffyness registered the reverse trend to
that of filled grains. Application of 180 kg N ha -1
produced significantly longer panicles than 120 kg N
ha -1 but at par with 150 kg N ha -1 which in-turn was
superior to 120 kg N ha -1 . However, the test weight
was similar with all the three doses of nitrogen. These
results corroborate the findings of Lateef (2010); Devi
and Sumathi (2011) and Rani (2012).
In general, the yield levels are low probably
due to severe Fe deficiency and termites incidence.
The grain yield of aerobic rice recorded with the
irrigation regime of maintenance of just soil saturation
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