RICE

1. COMPETITIVE PERFORMANCE OF RICE
VARIETIES WITH WEEDY RICE
R.M.U.S.BANDARA1,3, B. MARAMBE2
, A.P.BENTOTA3
, W.M.W.WEERAKOON4
,
H.M.M.K.K.H. DISSANAYAKA3 AND Y.M.S.H.I.U. DE SILVA3
1
Post Graduate Institute of Agriculture, University of Peradeniya, Peradeniya, Sri
lanka
2
Department of Crop Science, Faculty of Agriculture, University of Peradeniya, Sri
Lanka
3 Rice Research and Development Institute, Batalagoda, Ibbagamuwa, Sri Lanka
4
Ministry of Agriculture, Colombo, Sri Lanka

2. Introduction:
 Recently many farmers from heavy rice production areas such as
Ampara, Vavuniya, Kurunegala, Mathara, Puttalama complained that
their paddy fields cannot be cultivated due to weedy rice problem and
they informed that their yield losses due to the weeds range on 50-
100%.
 Today it was spreading irrespective of agro ecological zones and an
alarming rate, treaten food security in the country.
 In any crop or seeding system, weed-competitive cultivars should be
involved as a tool in integrated weed management strategies.

3. Introduction:
 Tall cultivars are usually more competitive against weeds, but they have
lower yield potential than short-statured modern cultivars.
 Tall cultivars may not be used widely in the future. Because of the ever-
increasing population, there will be more pressure in future farming to
produce more rice on less land.
 In such situations, growers may need to increase nitrogen fertilizer
rates and high nitrogen is known to cause crop lodging.
 Information on the effect of weed-competitive cultivars on weedy
rice is very limited in Asia.

4. Introduction:
Picture 01 – weedy rice infected rice fields

5. Justification
 In the absence of such information, the use of cultivars with the traits
of early vigor and quick canopy closure may help suppress weedy rice
growth. Short-duration cultivars that mature earlier than weedy rice
may also help in reducing the weedy rice seed bank .Therefore, this
study is very important to fill the knowledge gap on competitive rice
cultivars with weedy rice.
Objective
 To fill the knowledge gap on competitive rice cultivars with weedy rice.

6. Materials and Methods:
 Rice varieties screened.
Traditional (Suwandal, Pachchaperumal, Kaluheenati),
Old improved (H4, H7) and
New improved (Bg 250, Bg 251, Bg300, Bg 450, Bg 407H)
were screened against weedy rice.
 A field experiment conducted using a two factor factorial design.
Main factors were weedy rice and weedy rice free and
Sub factors were the selected rice varieties
 The expriment was conducted during maha 2016/2017 season at Rice
Research and Development Institute, Batalagoda.
 All crop management practices were done according to the
recommendation of the Department of Agriculture.

7. Materials and Methods:
 Weed control was done by applying Pretilachlor 300g/l EC at the
recommended rates.
 Final grain yields were measured
 Yield Reduction%= [(Yield under weedy rice free–Yield under weedy
rice infestation)/ Yield under weedy rice-free ]x 100.
 Weedy rice competitiveness= (Yield under weedy rice infestation
/Yield under weedy rice-free)]
 Data was analysed employing ANOVA and GLM procedures using
SAS software. Counts data were square root transformed prior to
analysis. Percentage data were arcsine transformed prior to analysis.

8. Materials and Methods:
Table 01. Levels of Weedy Rice Competitiveness defined based on the formulae
introduced by S. S. Harding and A. B. Jalloh, 2013 for Weed Competitiveness
Competitiveness Value Level of Competitiveness Abbreviation
0 to 0.50 Poor Competitiveness PC
0.51 to 0.60 Slightly Competitive SC
0.61 to 0.70 Moderately Competitive MC
0.71 to 0.80 Competitive C
0.81 to 0.90 Highly Competitive HC
0.91 to 1 Very Highly Competitive VHC

9. Materials and Methods:
Picture 02 – Research Experiment Photoes

10. Results and Discussion:
Table 02. yield reduction and weedy rice competitiveness
Variety % Yield
Reduction
Weedy Rice Competitiveness
Suwandal
23 b 0.77 Competitive
Pachchaperumal
48 ab 0.52 Slightly Competitive
Kaluheenati
37 ab 0.63 Moderately Competitive
H4
43 ab 0.57 Slightly Competitive
H7
46 ab 0.54 Slightly Competitive
Bg250
51 ab 0.49 Poor Competitiveness
Bg251
65 a 0.35 Poor Competitiveness
Bg300
60 a 0.40 Poor Competitiveness
Bg450
52 ab 0.48 Poor Competitiveness
Bg407H
59 a 0.41 Poor Competitiveness

11. As shown in table 02,
Suwandal showed the lowest percentage grain yield reduction due to
weedy rice infestation whereas Bg407H showed the significantly highest
grain yield reduction due to weedy rice infestation.
Suwandal was competitive.
Kaluheenati was moderately competitive.
Pachchaperumal, H4 and H7 were slightly competitive.
Bg250, Bg 251, Bg300, Bg450 and Bg407H showed a poor
competitiveness.
Chauhan (2013) reported that Short-duration cultivars that mature
earlier than weedy rice may also help in reducing the weedy rice seed
bank. But in our study short-durational varieties namely Bg250, Bg 251,
Bg300 showed a poor competitiveness.

12. Conclusion:
 Results revealed that different rice varieties showed different level of
weedy rice competitiveness.
 Suwandal was a competitive rice variety showing the lowest grain yield
reduction due to weedy rice infestation. Its competitiveness was 0.77.
 Kaluheenati was moderately competitive.
 Pachchaperumal, H4 and H7 were slightly competitive.
 Bg250, Bg 251, Bg300, Bg450 and Bg407H showed a poor
competitiveness.
 The experiment is to be conducted another season to come up with a
valid conclusion. These competitive rice varieties could be
incorporated in weedy rice management package.

13. References:
 Bhagirath S. C., 2013, Management strategies for weedy rice in Asia, Crop
and Environmental Sciences Division, International Rice Research Institute,
Los Baños, Philippines
 Harding S. S. and Jalloh A. B. (2013), Evaluation of the Relative Weed
Competitiveness of Some Lowland Rice Varieties in Sierra Leone, American
Journal of Experimental Agriculture; 3(2): 252-261
 Marambe, B. and L. Amarasinghe, (2000). Weedy rice in Sri Lanka. In Wild
and Weedy Rice in Rice Ecosystems in Asia – A Review (Eds: B.B. Baki,
D.V. Chin and A.M. Mortimer), pp 79-82. Limited Proceedings No 2.
International Rice Research Institute, Philippines.

14. Thank
You…….!