PhD

The experiment entitled "Productivity analysis of aerobic rice (Oryza sativa
L.) and its impact on green house gas emission" was undertaken at the Cropping
Systems Research Centre, Karamana, Thiruvananthapuram, during January to
May, 2011 and 2012. The main objectives of the-study were to standardise the
production techniques for aerobic rice, to study its water productivity as against
flooded rice and to assess the variation in green house gas emission under aerobic
and flooded situations. The entire study comprised two field experiments. The
first experiment (Part - I), entitled "Productivity analysis of aerobic rice against
conventional rice" was conducted during the summer season (January to May) of
2010- '11 and 2011-' 12. The second experiment (Part - 11) on "Agro techniques
for aerobic rice" was conducted during the summer season of 2011-' 12, to
standardize the agro techniques for the aerobic rice variety from Part - I.
Four rice varieties [VI: Aiswarya, V2: Uma, V3: MAS 946 - 1, V4: PMK (R)
3] were evaluated for their adaptabilityand performance both under flooded (W I)
and aerobic (W2) conditions, asPart ~ 1o,'Ihe experiment was laid out in RBD with
five replications (two separate layouts '(o~'flooded rice and aerobic rice). The agro
techniques study for aerobic rice, comprised two spacings (S I: 20 cm x 10 cm, S2:
15 cm x 10 cm), two nutrient levels (NI: 90:45:45 kg NPK ha", N2: 90:45:67.5 kg
NPK ha") and two methods of fertiliser application (AI: soil application, A2: soil
application + foliar application of K), laid out in RBD, replicated thrice. The
results of the study are as follows.
The variety, MAS 946 - 1 (V3) proved significant with respect to growth
and physiological parameters. The grain yield was maximum for MAS 946 - 1
(3.13 t ha-I under flooded, 2.85 t ha" under aerobic) accounting for about 10 per
cent increase over the next best varieties, Aiswarya and Uma.


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Flooded rice, in general yielded more than aerobic rice. However, the results
were significant only during the second year of experimentation, where the yield
variation between flooded rice and aerobic rice was 15.63 per cent. The average
water productivity of aerobic rice (0.75 kg m-3) was 70.4 per cent greater than that
of flooded rice (0.44 kg m'), MAS 946 - 1 recorded the maximum water
productivity of 0.48 kg m-3 and 0.80 kg m", under flooded and aerobic cultures
respectively.
The superiority of aerobic rice in mitigating green house gas (GHG)
emission from rice fields was revealed from the significantly lower efflux of
methane under aerobic (3.03 mg m-2 hr-I) compared to flooded rice (6.16 mg m-2
hr'). Though methane emission did not vary significantly among the varieties
under flooded culture, MAS 946 - 1 recorded significantly the least methane
efflux (14.08 mg m-2 hr') under aerobic system.
The benefit cost ratio (BCR) of flooded rice was 1.39 and that of aerobic
rice was 1.13 over the two years. MAS 946 - 1 recorded the highest BCR (1.40)
and was on a par with Uma (1.33) during the second year.
MAS 946 - 1 was selected as the best variety for Part - II of the study
based on its growth, physiology, yield and methane emission.
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The results of Part - II of the study revealed that wider spacing (S I: 20 cm
x 10 cm), higher nutrient level (N2: 90:45:67.5 kg NPK ha-I) and combined
method of nutrient application (A2: soil application + foliar application of K)
significantly increased productive tiller count (545.32 m"), grain weight per
panicle (2.83 g) and grain yield (3.28 t ha-I) ofMAS 946 - 1.
Aerobic nee culture is a prormsmg technology under water scarce
situations. Compared to flooded rice, the water productivity of aerobic rice was
70.4 per cent higher, methane emission was 50.8 per cent lower with a slight yield



reduction of 15.63 per cent. Among the four varieties tested, MAS 946 - 1, the
first aerobic rice variety released from VAS, Bengaluru and Aiswarya and Uma,
KAV rice varieties, proved superior for aerobic conditions under Kerala
situations.
It can be concluded that the performance of the variety, Uma is as good as
MAS 946 - 1 for cultivation under aerobic condition in the lowlands of Kerala. A
recommended spacing of 20 cm x 10 cm with a nutrient schedule of
90 kg N, 45 kg P20S and 60 kg K20 as soil application along with 7.5 kg K20 per
hectare as foliar application was found as the best agronomic package for rice
under aerobic situation.