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Allelopathic potential of Goose weed (Spehenoclea zelanica) on Rice Weeds in Sri Lanka

A.S.K. Abeysekera 1, H.M.S. Herath 1 and U.B. Wickrema1

1Rice Research and Development Institute, Batalagoda, Ibbagamuwa Sri Lanka. E.mail anuru@slt.net.lk

Abstract

Goose weed (Spehenoclea zelanica), family Spehenocleace, is a common broad leaf weed in rice fields in SriáLanka. We studied the allelopathic potential of Goose weed in submerged rice soils incorporated with problematic grass weeds and on rice plants at the Rice Research and Development Institute, Sri Lanka during 2003/2004 major and 2004 minor seasons. Seedlings of Goose weed were grown in 30 x 30 cm pots. Six week old plants were uprooted and chopped and about 400 -600 g of chopped residues were mixed with 5 kg soil and incubated for one week. Pre germinated rice seeds, seeds of Echinochloa crus-galli, Leptochloa chinensis and Ischne globosa having more than 80% germination were sown onto these soils in separate pots. Control treatments were maintained as untreated with Goose weed residues. The results showed that soil incorporated Goose weed significantly inhibited the germination and growth of E. crus-gali and L. chenensis. It did not have any effect on rice and I. rugosum. Shoot length, tiller count, leaf area and biomass production of E. crus-gali, L. chenensis grown with Goose weed incorporated soil were significantly lower than those in the untreated soil. These results indicate that soil incorporated Goose weed plants have allelopathic potential to inhibit the germination, growth and development of two major grass weed, E. crus-gali and L. chenensis but no effect on I .rugosum. Goose weed residues had no effect on rice seed germination, growth and yield in submerged soil.

Media summary

Allelopathic potential of Goose weed to control Echinocloa crus-galli and Leptocloa chinensis in wet seeded rice field was reported by weed scientist at RRDI Sri Lanka.

Key words

Allelopathy, Echinochloa crus-gali, Goose weed, Leptochloa chinensis, Rice

Introduction

Goose weed (Sphenoclea zeylanica) is a common dominant annual broad leaf weed in wet seeded rice fields in Sri Lanka. It grows all year round and was becoming a serious weed in direct seeded and transplanted rice. It is a 60-100 cm tall, fleshy marsh herb with erect stem having many branches which is propagated by seeds. The seeds are yellowish brown and fruit is flash globose capsule. Lekkong and Wanichanantakul (1995) reported that most broad leaf weeds contain more than 1% N and incorporation of these weeds increases soil fertility. .It further indicated that the analytical studies showed goose weed contain percentage of N: 2.96▒0.1, P: 0.44▒0.01, K: 2.06▒0.04, Ca: 0.48▒0.02, Mg:0.30▒0.02, S:0.57▒0.07 .Goose weed was identified as an allelopathic weed and decomposed plant residues in submerged soil can inhibit growth and delay flowering of White head (Eclipta thermalis) Red sprangle top (Leptochloa cheinensis) and Barnyard grass (Echinochloa crusgalli) (Premasthira and Zungsonthiporn, 1985, 1990, and 1995). Premasthira and Zungsonthiporn (1999) further indicated that the plant growth inhibitor in Goose weed was released in to the environment by root exudation and it was identified as Thiosulfinate and Secoiridoids glucoside. The objective of this study was to investigate the allelopathic potential of soil incorporated Goose weed on problematic lowland grassy weeds and rice in Sri Lanka.

Methods

The experiment was conducted at the Rice research and Development Institute, Sri Lanka during 2003/2004 major and 2004 minor season. One week old seedlings of Goose weeds were planted in 30 x 30 cm pots and allowed to grow for six week until flowering. Those plants were then up rooted, chopped into small pieces. About 400-600 g of chopped Goose weeds were mixed with 5 kg soil per pot and incubated for one week. Fifteen seeds of pre germinated rice, E.crusgalli , L chinensis and I .rugosum, which are more than 80% viable, were sown separately into those incubated pots containing submerged rice soil. Pots without incorporating Goose weed with soil were treated as control. Water management fertilizer and other cultural management were done uniformly in each treatment. Each treatment was replicated three times.

Germination of test species was counted at 2, 4 weeks after sowing (WAS). Three seedling of test plants in each treatment were uprooted and shoot length, tiller number, leaf area and dry weight were measured at 6 WAS. Rice plants were allowed to grow and yield and yield component were measured at harvest.

Results and Discussion

Germination of Test Plant.

Germination of rice seeds did not have any significant reduction in Goose weed treated and untreated soils in both seasons (Table 1). This suggest there was no detrimental effect on germination of rice seedlings with decomposing Goose weeds in rice fields. There was a significant reduction in germination of E. crusgalli and L. chinensis with the incorporation of Goose weed when compared that with the untreated pots (Table 1).However, there was no significant difference in germination of I. rugosum between Goose weed treated and untreated treatments in both season. These results showed that the impact of decomposed Goose weed residues differ among weed species in submerged rice soil.

Table 1. Effect of soil incorporated decomposed Goose weed on germination of Oryza sativa, I. rugosum E. crusgalli and L. chinensis at two weeks after sowing.


Treatments

Number of germinated seedlings

O.sativa

E. crussgalli

I. rugosum

L. chinensis

 

Major

Minor

Major

Minor

Major

Minor

Major

Minor

Treated soil

15 a

14 a

9 b

6 b

11 a

12 a

8 b

6 b

Untreated soil

12 a

15 a

18 a

14 a

13 a

10 a

11 a

14 a

Means followed by the same letter in each column are not significantly different at p = 005, DMRT.

Growth and Development of Test Plant.

Soil incorporated decomposed Goose weed had strong inhibitory effect on shoot length, tiller count and dry matter production of E. crusgalli and L. chinensis. However, leaf area and root biomass per plant did not vary (Table 2). The decomposed Goose weed residues did not have any significant impact on shoot length and tiller count of rice plants.

A marginal reduction in leaf area and dry matter production of rice plants were however observed with soils treated Goose weed but statistically not significant in both season. However, Premasthira et al. (1985), reported that methanol extracted solution of 1, 5 and 10 gram equivalent to fresh weight of Goose weed had strong inhibitory effect on growth of rice seedlings.These contrast results may be due to concentration of chemicals released by Goose weed plants with different exudates, extraction procedures and decomposition rates.

Table 2. The effect of soil incorporated decomposed Goose weed on shoot length,tiller count and dry weight of E. crusgalli, L. chinensis, I. rugosum and O. sativa at 6 WAS

Treatment

Shoot length (cm)

Tiller count (no/plant)

Dry weight (g/plant)

E. crusgalli

Treated

43.5b

3.2b

3.1b

Untreated

68.5a

5.1a

6.4a

L. chiensis

Treated

31.3b1

2.3b1

1.8b1

Untreated

52.4a1

4.5a1

3.4a1

I. rugosum

Treated

38.3a2

4.3a2

3.2a2

Untreated

36.4a2

4.0a2

3.6a2

O. sativa

Treated

46.5a3

3.2 a3

2.6 a3

Untreated

36.4a3

4.6 a3

3.0aa3

Means followed by the same letter in each column are not significantly different at p=005 , DMRT.
There was no significant difference in shoot length, tiller number and dry matter production of I. rugosum between soil treated with Goose weed residues and untreated control. This indicates that the soil incorporated Goose weed plant residues did not effect the germination and growth of I. Rugosum

Yield and yield component of rice

The effect of soil incorporated decomposed Goose weed on the yield and yield component of rice were shown in Table 3. No significant different yield and yield component of rice were observed from soil treated Goose weed and untreated pots.

Table 3. Effect of soil incorporated decomposed Goose weed on the yield and yield components of rice at harvest.

Treatment

No panicle/
hill

No grain/ panicle

1000 grain weight (g)

Yield (g)/
hill

Treated

4.3a

120

21.4

18.4

Untreated

3.9

108

19.5

16.4

 

ns

ns

ns

ns

Ns-no significant difference

Conclusion

The data indicates that Goose weed, which is becoming a dominant broad leaf weed in wet seeded rice fields in Sri Lanka, has allelopathic potential to control two problematic grass weeds such as E. crus-galli and L. chinensis. It has no effect on germination and growth of I. rugosum.

The decomposed Goose weed in submerged condition did not show any detrimental effect on germination growth and yield of rice. These allelopathic characters of soil incorporated Goose weed plants can be identified as a biological control method and could be included as a practice for integrated weed management. Further more this problematic Goose weed Sphenoclea zelanica could therefore be utilized to increase soil fertility as well as to control two dominant grass weeds in wet seeded rice in Sri Lanka.

References

Lekkong P and Wanichanantakul P (1995). Nutrient content of some weed species. Proc. 1(B). The 15th conference of the Asian-pacific Weed Science Society Conference. P 488-492.

Premasthira C and Zungsontiporn S (1985). Plant growth inhibiting effects of weed species with reference to allelopathy, Proc. 2. The tenth conference of the Asian-pacific Weed Science Society Conference. P 458-462.

Premasthira C and Zungsontiporn S (1990) Influence of allelopathic substances from Sphenoclea zeylanica Gaertn. On growth of weeds. Thai Agricultural Research Journal 8 : 29-34.

Premasthira C (1995). Allelopathic potential of goose weed (Sphenoclea zeylanica gaertn.). The fifteenth Asian Pacific Weed Science Society Conference. P 559 – 562.

Premasthira C (1997). Allelopathy of goose weed (Sphenoclea zeylanica gaertn.).The seventeenth Asian Pacific Weed Science Society Conference. P 21–32.

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