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

1Post Graduate Institute of Agriculture, University of Peradeniya, Peradeniya, Sri lanka

2Department of Crop Science, Faculty of Agriculture, University of Peradeniya, Sri Lanka

3 Rice Research and Development Institute, Batalagoda, Ibbagamuwa, Sri Lanka4 Ministry of Agriculture, Colombo, Sri Lanka

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.

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.

Introduction: Picture 01 – weedy rice infected rice fields

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.

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.

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.

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

Materials and Methods: Picture 02 – Research Experiment Photoes

Results and Discussion: Table 02. yield reduction and weedy rice competitiveness

Variety % Yield

Reduction

Weedy Rice Competitiveness

Suwandal23 b 0.77 Competitive

Pachchaperumal48 ab 0.52 Slightly Competitive

Kaluheenati37 ab 0.63 Moderately Competitive

H443 ab 0.57 Slightly Competitive

H746 ab 0.54 Slightly Competitive

Bg25051 ab 0.49 Poor Competitiveness

Bg25165 a 0.35 Poor Competitiveness

Bg30060 a 0.40 Poor Competitiveness

Bg45052 ab 0.48 Poor Competitiveness

Bg407H59 a 0.41 Poor Competitiveness

CV36 *** ***

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.

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.

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.

Thank You…….!