05 Begum M - Universiti Kebangsaan Malaysia

Malays. Appl. Biol. (2005) 34(2): 31–41

WEED DIVERSITY OF RICE FIELDS

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WEED DIVERSITY OF RICE FIELDS IN FOUR DISTRICTS OF MUDA RICE GRANARY AREA, NORTH-WEST PENINSULAR MALAYSIA BEGUM, M.1, JURAIMI, A.S.1, AZMI, M.3, RAJAN, A.1 and SYED-OMAR, S.R.2 1Department

3

of Crop Science and Department of Land Management, Universiti Putra Malaysia, 43400 Serdang, Selangor E-mail: [email protected] 2MARDI, Pulau Pinang

ABSTRACT A survey was conducted to determine the major weeds of rice fields in 4 districts (District I, II, III and IV) of Muda rice granary area, Peninsular Malaysia, from 5-20 July 2003. Rice fields surveyed covering of 27 farm blocks with 579 fields. A total of 35 weed species belonging to 17 families were recorded, of which 15 species were broadleaved, 10 sedges, 6 grasses and 4 aquatics. Species diversity ranking of weed community for the districts were District-II > District-III > District-IV > District-I. Sorenson’s index of similarity indicated that at least 82.76% of the listed species occurred in 4 districts. Out of 35 infested weed species, 6 species were determined as dominant based on rating score (2 to 5) of weed infestation and percent infested fields (> 40 %). Oryza sativa (weedy rice) ranked top among all districts followed by Leptochloa chinensis, Echinochloa crus-galli, Ischaemum rugosum, Ludwigia hyssopifolia, and Fimbristylis miliacea in the District II, District III and District IV, whereas, in District I Sphenoclea zeylanica was prevalent instead of Ischaemum rugosum.

ABSTRAK Bancian telah dilakukan untuk menentukan rumpai-rumpai utama di empat daerah kawasan tanaman padi Muda, Semenanjung Malaysia dari 5 hingga 20 Julai 2003. Sebanyak 579 sawah dari 27 blok telah dibanci. Sejumlah 35 spesies rumpai dari 17 famili direkodkan iaitu 15 spesies rumpai berdauan lebar, 10 rusiga, 6 rumput dan 4 akuatik. Kepelbagaian spesies rumpai di setiap daerah mengikut susun atur dari yang lebih tinggi kepada yang rendah ialah Daerah II>Daerah III> Daerah IV>Daerah I. Indek keserupaan Sorenson’s menunjukkan sekurang-kurangnya 82.7% spesies yang disenaraikan terdapat di ke empat-empat daerah yang dikaji. Daripada 35 spesies yang direkodkan 6 spesies dikenalpasti sebagai dominan berdasarkan skor (2 hingga 5) rumpai yang meliputi dan peratus sawah yang diliputi rumpai (> 40%). Oryza sativa (Komplek) (Padi Angin), dikenalpasti sebagai rumpai paling dominan diikuti oleh Leptochloa chinensis, Echinochloa crus-galli, Ischaemum rugosum, Ludwigia hyssopifolia dan Fimbristylis miliaceae di Daerah II, III dan IV. Keadaan yang sama juga didapati untuk Daerah I juga mempunyai susun atur yang sama kecuali rumpai Sphenoclea zeylanica lebih utama berbanding Ischaemum rugosum.

Key words: weed diversity, rice, Muda rice granary, Malaysia

INTRODUCTION Rice is the 3rd most important crop in Malaysia, which is mainly grown in eight granary areas in Peninsular Malaysia covering an area of about 209,300 ha (Suhaimi et al., 1987). One of the largest granary is Muda (98,860 ha) in Kedah divided into 4 districts. In this area, direct seeding * To whom correspondence should be addressed.

has been practiced since 1980s. Due to the changes in cultural practices, this direct-seeded fields lead to aerobic condition and are not flooded during initial crop growth. These conditions are more conducive to weed growth, especially the more competitive grassy weeds (Moody and De Datta, 1982). In the early 1990’s, at least 100 million tones of rice produced in Asia were lost annually due to infestation of weeds (Watson et al. 1997).

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The total annual worldwide loss of rice due to weeds was found to be 15% (De Datta, 1990) and 41 to 70% in Malaysia (Azmi, 1988). Weeds represent a major constraint by yield loss between 5 to 72% depending on season of crop sowing, weed species, weed density, rice cultivars, growth rate and density of weed and rice (Ho, 1984; Kuan et al., 1990). Therefore, weed management is a necessary prerequisite to overcome the production loss through weeds. Effective weed control requires knowledge of taxonomy, distribution, ecology and biology of weeds (De Datta, 1988). Weed distribution is the result of the compound influence of ecological and human factors. The composition of the weed flora may differ depending on location (Janiya and Moody, 1983), water supply (Bhan, 1983), cultural practices (Bernasor and De Datta, 1983; Mabbayad et al. 1983; Janiya and Moody, 1989), the inherent weed flora in the area, and the crop grown. Surveys on the rice weed community in Muda area have been reported by Azmi et al. (1993). Among 40 weed species the dominant species identified were Echinochloa crus-galli, Leptochloa chinensis, Fimbristylis miliacea, Scirpus grossus, Monochoria vaginalis and Sphenoclea zeylanica. Pane (1997) reported that Leptochloa chinensis was the most important weed species out of 13 weed species in Muda area followed by Fimbristylis miliacea, Echinochloa crus-galli and Ludwigia octovulvis. The infestation pattern of weed species in Muda area was changed between their surveys due to continuous adoption of a single weed control method. Repeated use of a particular herbicide greatly influenced weed species composition and dominance. Ho and Zakaria (1995) observed that widespread use of molinate herbicide which selectively suppressed Echinochloa crus-galli has resulted in the gradual increase of Leptochloa chinensis. The plots repeatedly applied with 2-4 D amine resulted in drastic increased of Echinochloa crus-galli (Azmi, 2002) and Fimbristylis miliacea (Watanabe et al., 1997), whereas effective in suppressing Scirpus grossus, and Monochoria vaginalis, (Azmi, 2002). Therefore, Moody (1990) stated that herbicide use moves the agroecosystem towards low species diversity with new problem weeds appearing, stressing the need for an ecological approach to weed control. Moreover, annual weeds react very quickly to alternation of their environment. Thus, the weed flora of a place changes during the year, and from year to year following the weather condition (Holzner, 1982). Thus, information on the up-to-date presence, composition, abundance, importance and ranking of weed species that infest in Muda area according to four districts was needed to reformulate

appropriate weed management strategies to produce optimum yields of rice. Site specific knowledge on the nature and extent of infestation of weed flora through weed surveys is essential in the planning of their control rather, than a countrywide blanket recommendation using standard herbicides and doses. Therefore, the present study was under taken to investigate the current status of troublesome weeds including composition, distribution, severity and structure of weed communities prevailing at the four districts in Muda area.

MATERIALS AND METHODS The survey was conducted in direct seeded rice crop in Muda at Kedah from 5 to 20 July, 2003. Weed infestations were assessed at rice heading stage. Farmers had weeded and applied herbicides to the rice fields when the surveys were conducted. Rice fields surveyed covering the 4 districts (District-I, District-II, District-III and DistrictIV) comprised of 27 farm blocks with 579 fields (Figure 1 and 2). For District-I, II, III and IV, the number of farm blocks and respective fields was 5, 9, 7, and 6, and 97, 160, 110 and 212, respectively. Before starting the survey a route was planned to provide adequate coverage of the whole area. All fields along to the route were assessed irrespective of size. Visual assessments were made on the occurrence and density of individual weed species by two persons walking along one side and again when returning along the opposite side of the field. A mean score for each weed was then determined. The percentage cover of weeds prevailing above the rice canopy was based on the whole field, whereas the percentage cover of weeds below the crop canopy was taken from four randomly selected 1 m2 quadrats placed on each side of the rice field. This method was adapted both to reduce the time taken to survey a field and to prevent possible damage to the crop (Elazegul et al., 1990). Each field was surveyed by searching field margins and headlands in detail. Field margins and headland infestations of different species were not recorded because they were usually not representative of the field as a whole. When odd plants or patches of a weed occurred only at a distance, these were visited to make absolutely sure of their identity. Care was taken in the identification of weed species. As most grasses were in the flowering stage assessments could be made quite readily. Where several grasses occurred together, particular care was also taken in assessing their relative proportions. Species that could not be identified were tagged, pressed and


Fig. 1. Rice cultivation areas in Peninsular Malaysia (Muda area).

Fig. 2. Four Districts of Muda area in Peninsular Malaysia which survey was conducted.

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submitted for positive identification (Chancellor and Froud-Williams, 1982; 1984). All weed species present were recorded and scored for distribution and frequency. A rating scale of 1 to 10 was used to denote weed cover (Pablico and Moody, 1985; Elazegul et al., 1990), the lowest score of 1 = 1-10% weed cover, while the maximum score of 10= 91-100% weed cover. Species with a few scattered plants were coded as Tr. (Trace amounts). Comparison of species affiliation among weed communities between districts were made using the “Sorenson’s Index of Similarity” (S) (Goldsmith et al., 1986). Computation of the S values was as follows: S=

2J A+B

x 100

Where, S = Comparison of association between district A and B J = Number of species common to both A and B A= Number of species present at district A B = Number of species present at district B Higher S value indicates close similarity in species composition between districts. Conversely, lower S values reflect divergence in species composition in the two districts.

RESULTS AND DISCUSSION Weed species distribution Occurrence of 35 weed species belonging to 17 families were recorded in Muda rice granary, of which 15 were broadleaved, 10 sedges, 6 grasses, and 4 aquatic, respectively (Table 1). The highest number of species (10) was found in Cyperaceae family followed by Gramineae (6), Scrophulariaceae (3), Onagraceae (2) and Pontederiaceae (2). Rests of the 12 families were represented by one species each. Species composition under different families were generally uniform, but with a few exceptions. The family Salviniaceae and Hydrocharitaceae were absent in district-I, III and IV. The family Parkeriaceae was absent in District-III, while in District-IV the family Gentiaceae was absent. In District-I the number of species under Cyperaceae family was lower compare to the other 3 districts (Table 1). The number of species recorded in 4 districts ranged from 28 to 31 (Table 2). District-II and III appeared to be the most diversified with 31 species under 17 and 14 families, respectively; while

District-I registered 28 species grouped under 15 families (Table 2). Species diversity ranking for the districts were as follows District-II, District-III > District-IV > District-I (Table 2). The difference in the number of species in between the districts were likely due to the occurrence of minor species (> 0.47 – 3.64 % of fields infestation) (Table 2). Nine weed species, viz. Oryza sativa complex (weedy rice), Echinochloa crus-galli, Leptochloa chinensis, Ludwigia hyssopifolia, Fimbristylis miliacea, Ischaemum rugosum, Scirpus grossus, Cyperus iria and Sphenoclea zeylanica were the most frequent (more than 20% field infested) in District-I and II (Table 2). In District-III and IV eight weed species were the most frequent (more than 20% field infested) namely Oryza sativa complex (weedy rice), Echinochloa crus-galli, Leptochloa chinensis, Ludwigia hyssopifolia, Fimbristylis miliacea, Ischaemum rugosum, Scirpus grossus, and Cyperus iria. Cyperus babakensis was frequent instead of Cyperus iria in District-III. Rests of the species were less evenly distributed with low percent infestation (1 to 17%). Scirpus lateriflorus, Scirpus juncoides, Cyperus haspan, Salvinia cucullata, Blyxa malayana, Fuirena umbellata and Monochoria hastata were not found in District-I while Eleocharis variegata, Lindernia pusilla, Fuirena umbellata and Monochoria hastata were not observed in District-II. Ceratopteris thalictroides, Eleocharis variegata, Blyxa malayana, and Salvinia cucullata were absent from District-III and Ludwigia adscendens, Nymphoides indica, Eleocharis variegata, Blyxa malayana and Salvinia cucullata were not found in District-IV. High values of Sorenson’s index (82.76% to 95.08%) indicated close similarity in weed species in all districts (Table 3). The highest similarity value of 95.08% was between District-III and District-IV, while the lowest value of Sorenson’s index was 82.76% between District-I and DistrictIV followed by District-II and District-III (85.14%). Comparison of District-I with both District-II and District-III recorded a similar index of 88.14%. This may be explained by the closeness of District-III and District-IV compared to the District-1 and District-IV. Perhaps, similar cultural practices and water regimes prevailed between the District-III and District-IV compared to between District-I and District-IV. On the other hand, in District-1 a more favourable water regime may explain the comparatively higher occurrence of aquatic weeds with lower number of sedges than District-IV. Tomita et al. (2003) observed that impact of direct seeding with rich water conditions on paddy vegetation is small in terms of species diversity and species composition. Data on percent fields infested by weed types are shown in Figure 3. The hierarchy in decreasing

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Table 1. Distribution of weed species based on family affiliation and weed type in four districts of Muda rice granary area1

Weed occurrence Family

Species Dist.-I

Dist.-II

Dist.-III

Dist.-IV

Aquatics (submerged) Gentiaceae

Nymphoides indica (L.)O.k

x

x

x

–

Hydrocharitaceae

Blyxa malayana Ridl

–

x

–

–

Lentibulariaceae

Utricularia aurea Lour.

x

x

x

x

Najadaceae

Najas graminea (non Del.) Ridley.

x

x

x

x

Alismataceae

Sagittaria guayanensis H.B.K.

x

x

x

x

Butomaceae

Limnocharis flava (L.) Buchenau

x

x

x

x

Lemnaceae

Lemna perpusilla Torr.

x

x

x

x

Marsileaceae

Marsilea crenata Presl

x

x

x

x

Onagraceae

Ludwigia hyssopifolia (G. Don) Exell

x

x

x

x

Ludwigia adscendens (L.) Hara

x

x

x

-

Broad-leaved weeds

Parkeriaceae

Ceratopteris thalictroides (L.) Brongn.

x

x

–

x

Pontederiaceae

Monochoria vaginalis (Burm.f.)

x

x

x

x

Monochoria hastate (L.) Solms

–

–

x

x

Rubiaceae

Hedyotis corymbosa (L.) Lamk.

x

x

x

x

Salviniaceae

Salvinia cucullata Roxb. ex Bory

–

x

–

–

Scrophulariaceae

Bacopa rotundifolia (Michx.)Wettst.

x

x

x

x

Limnophila erecta Benth.

x

x

x

x

Lindernia pusilla Boldingh

x

–

x

x

Sphenoclea zeylanica Gaertn.

x

x

x

x

Echinochloa crus-galli (L.) Beauv.

x

x

x

x

Echinochloa colonum (L.) Link

x

x

x

x

Ischaemum rugosum Salisb.

x

x

x

x

Leptochloa chinensis (L.) Nees

x

x

x

x

Spenocleacea

Grasses Gramineae

Oryza sativa complex (weedy rice)

x

x

x

x

Paspalum vaginatum Sw.

x

x

x

x

Cyperus babakensis steud.

x

x

x

x

Cyperus difformis L.

x

x

x

x

Cyperus haspan L.

-

x

x

x

Sedges Cyperaceae

Total 1 weeds

Cyperus iria L.

x

x

x

x

Eleocharis variegata (nec kunth) Boeck.

x

–

–

–

Fimbristylis miliacea (L.) Vahl

x

x

x

x

Fuirena umbellata Rottb.

–

–

x

x

Scirpus grossus L.f

x

x

x

x

Scirpus juncoides Roxb.

–

x

x

x

Scirpus lateriflorus Gmel.

–

x

x

x

35

28

31

31

30

arranged in alphabetical order of Family; x = present; - = absent

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Table 2. Occurrence of weed species in 4 district of Muda Rice granary areas (% of fields infested)

Weed Species

District -I

District- II

District -III

District- IV

100.00

100.00

98.18

100.00

Echinochloa crus-galli

93.81

86.88

76.36

91.04

Leptochloa chinensis

85.56

90.00

82.72

88.68

Ludwigia hyssopifolia

59.79

78.13

71.81

63.21

Fimbristylis miliacea

48.45

51.25

51.81

45.75

Ischaemum rugosum

20.61

43.13

67.27

48.58

Scirpus grossus

29.89

42.50

41.81

30.66

Cyperus iria

21.64

33.75

8.18

34.91

Sphenoclea zeylanica

40.21

30.63

3.63

12.26

Echinochloa colona

4.12

10.63

14.54

9.91

Bacopa rotundifolia

4.12

13.13

9.09

10.38

Oryza sativa (weedy rice)

Cyperus babakensis

1.03

6.88

24.55

7.08

Limnocharis flava

11.34

5.00

13.63

6.60

Utricularia aurea

12.37

9.38

12.72

1.42

Monochoria vaginalis

5.15

8.75

12.72

4.72

Sagittaria guyanensis

3.09

6.25

10.90

6.60

Cyperus difformis

16.49

5.63

4.55

4.25

Marsilea crenata

10.30

4.38

8.18

1.89

Najas graminea

11.34

5.63

0.90

3.30

Limnophila erecta

4.12

3.13

9.09

1.42

Lemna perpusilla

8.24

3.13

0.90

1.42

Ceratopteris thalictroides

7.21

1.88

–

1.89

Hedyotis corymbosa

2.06

3.13

1.81

1.89

Ludwigia adscendens

6.18

1.25

3.63

–

Paspalum vaginatum

1.03

1.25

0.90

2.83

Nymphoides indica

6.18

0.63

0.90

–

Eleocharis variegata

1.03

–

–

–

Lindernia pusilla

1.03

–

0.90

0.47

Scirpus lateriflorus

–

0.63

3.64

0.47

Scirpus juncoides

–

0.63

1.81

0.94

Cyperus haspan

–

0.63

1.81

2.36

Salvinia cucullata

–

0.63

–

–

Blyxa malayana

–

2.5

–

–

Fuirena umbellata

–

–

1.81

1.42

Monochoria hastata

–

–

2.73

0.47

Table 3. Sorenson’s index of similarity in weed species among the four districts in Muda rice granary areas Districts

District-I

District-II

District-III

District-IV

District-I

–

88.14

88.14

82.76

District-II

88.14

–

90.32

85.25

District-III

88.14

90.32

–

95.08

District-IV

82.76

85.25

95.08

–


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Fig. 3. Weed communities in different districts of Muda rice granary areas.

order was grasses (G) > broadleaved weeds (BL) > sedges (SG) > aquatics (AQ) in the District I, II, and III, while in District IV the order was G > SG > BL> AQ. The hierarchical importance of weed groups were almost similar between DistrictII and III, but varied considerably between District-I and District-IV. The difference in hierarchical importance of different weed groups between these districts arguably also reflects differences in agronomic practices, especially water management. Azmi et al. (1993) observed that the hierarchical importance of weed type (grasses, broadleaved weeds, sedges and aquatics) varies considerably between and within each rice granary due to difference microclimatic and agronomic practices prevailing in those areas. These variations in distribution of species also indicate differences in the invasiveness of the species, ecological and edaphic preferences, previous cultural practices and herbicide use (Froud-Willams and Chancellor, 1987). Severity of weed infestation Rice fields ranged from 98.18 to 100% infested by Oryza sativa (complex) followed by Echinochloa crus-galli (76.36 - 93.81%), Leptochloa chinensis (82.72 - 90%), Ludwigia hyssopifolia (59.79 - 78.13%), Ischaemum rugosum (20.61 - 67.27%), Fimbristylis miliacea (45.75 – 51.81%), Scirpus grossus (29.89 - 41.81%), Sphenoclea zeylanica (3.63 - 40.21%) and Cyperus iria (8.18 – 34.91%) in District-I, II, III and IV (Table 2). The scores for level of occurrence of the 8 to 9 most frequent weed (> 20% fields infested) among 4 districts are given in Table 4. Severe infestation (score 4 or 5) were recorded on Oryza sativa in all 4 districts followed by Echinochloa

crus-galli in District-I, Leptochloa chinensis in District-II and IV and Ischaemum rugosum in District-II and III. Most widespread infestations (score 2 to 3) were of Leptochloa chinensis (14 fields), Fimbristylis miliacea (5 fields), Scirpus grossus (5 fields), Sphenoclea zeylanica (3 fields) and Ischaemum rugosum (2 fields) in District-I. In District-II most widespread infestation were of Echinochloa crus-galli (15 fields), Ludwigia hyssopifolia (2 fields), Fimbristylis miliacea (2 fields) and Scirpus grossus (2 fields). In case of District-III the widespread infestation were of Leptochloa chinensis (6 fields), Echinochloa crusgalli (6 fields), Ludwigia hyssopifolia (1 fields), Fimbristylis miliacea (1 fields), and Scirpus grossus (1 fields), whereas in District-IV widespread infestation occurred on Echinochloa crus-galli (30 fields), Ischaemum rugosum (8 fields), Fimbristylis miliacea (2 fields), Scirpus grossus (1 fields) and Sphenoclea zeylanica (2 fields). Other 2 species Ludwigia hyssopifolia and Cyperus iria were frequent but occurred only trace to 10% weed coverage in District-I and District-IV, whereas Cyperus iria and Sphenoclea zeylanica observed (trace to 10% field coverage) in District-II and Cyperus babakensis in District-III. In any one ricefields the dominant weed flora is usually about ten species, of which the dominant ones rarely are more than 3 to 4 (Moody and Drost, 1983). Therefore, considering the six most abundant weed species (rating score 2-5 and more than 40% fields infested) in each district and their ranking in decreasing order of dominant species were Oryza sativa> Leptochloa chinensis> Echinochloa crus-galli> Ischaemum rugosum> Ludwigia hyssopifolia> Fimbristylis miliacea in District-II, III and IV. Whereas, in District-I the hierarchical order of abundant

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Table 4. The occurrence at six level of frequency of most abundant weed species in direct seeded rice in the four Districts of Muda area

Weed infestation (% cover)a

Weed Species Tr

1

2

3

Total number of fields infested 4

5

District-I (Total fields surveyed 97)

Oryza sativa

28

36

16

11

2

4

097


45

20

18

6

1

1

091


44

25

11

3

–

–

083


50

8

–

–

–

–

058


37

5

5

–

–

–

047


17

19

3

–

–

–

039

Scirpus grossus

21

3

5

–

–

–

029

Ischaemum rugosum

10

8

1

1

–

–

020

Cyperus iria

14

7

–

–

–

021

District-II (Total fields surveyed 160)

Oryza sativa

63

33

43

10

6

1

156


100

37

4

1

1

1

144


100

24

13

2

–

–

139


109

14

2

–

–

–

125


71

9

1

1

–

–

082

Ischaemum rugosum

38

19

8

2

2

–

069

Scirpus grossus

50

16

2

–

–

–

068

Cyperus iria

52

2

–

–

–

–

054


42

7

–

–

–

–

049

District-III (Total fields surveyed 110)

Oryza sativa

28

40

18

12

3

5

108


58

27

3

3

–

–

091


61

17

5

1

–

–

084


71

7

1

–

–

–

079

Ischaemum rugosum

36

24

9

3

1

1

074


52

4

1

–

–

–

057

Scirpus grossus

36

9

1

–

–

–

046

Cyperus babakensis

26

1

–

–

–

–

027

District-IV (Total fields surveyed 212)

Oryza sativa

64

54

47

35

12

–

212


105

58

26

4

–

–

193


76

70

33

5

4

–

188


125

9

–

–

–

–

134

Ischaemum rugosum

69

26

7

1

–

103


84

11

2

–

–

–

097

Cyperus iria

67

7

–

–

–

–

074

Scirpus grossus

55

9

1

–

–

–

065

aRating scale: Tr = a few scattered plant, 1 = 1-10% weed cover; 2 = 11-20% weed cover; 3 = 21-30% weed cover; 4 = 31-40% weed cover; 5 = 41-50% weed cover.


species were Oryza sativa> Echinochloa crus-galli> Leptochloa chinensis> Ludwigia hyssopifolia> Fimbristylis miliacea> Sphenoclea zeylanica. Ischaemum rugosum infestation was very low in District-I, only 20.61% field infestation and Sphenoclea zeylanica infestation was higher than other Districts. Watanabe and Azmi (1995) noted that Ischaemum rugosum did not persist as viable buried seeds under continuously flooded or periodically flooded field conditions whilst 10.5% were still viable after 3 years (6 cropping seasons) in dry land. Therefore in District-I may be higher water regime compare to other districts which reduced the Ischaemum rugosum infestation and increase the Sphenoclea zeylanica infestation. This study revealed that there was a gradual increase in grassy weeds in all four districts of Muda area compared to the previous studies conducted by Azmi et al. (1993) and Pane (1995). They found that the predominant position of grasses such as Echinochloa crus-galli and Leptochloa chinensis were the key species in Muda area. According to Azmi (1994), Supaad et al., (1991), and Ho and Zuki, (1988) in the Muda rice growing area, the method of cultivation practice shifted from transplanting to direct seeding of rice resulted in the increase of grassy weeds notably Echinochloa crus-galli (L.) P. Beauv., Leptochloa chinensis (L.) Nees, Echinochloa colonum (L.) Link. and Ischaemum rugosum Salisb. From this study it has been observed that grassy weed components are dominated by Oryza sativa complex (weedy rice), while Leptochloa chinensis, Echinochloa crus-galli and Ischaemum rugosum are important. Oryza sativa complex (weedy rice) appeared sporadically in southern part of Muda area in 1990. Severe infestations occurred in 1993 and the affected area increased in 1994 (Ho and Zainuddin, 1995). Generally, three factors that determine the population growth of weedy rice are: seed remaining dormant in the soil over crop seasons; dissemination through crop seed contamination; and seed return from plants in the previous crop (Mortimer et al. 2000). Vaughan et al. (2003) suggested that the wide spread occurrence of weedy rice in Malaysian rice culture has been favoured by (i) the practices of direct seeding and volunteer seedling rice culture, (ii) the use of easy shattering varieties and (iii) the use of combine harvesters, which moved from one rice growing area to another. In this study Leptochloa chinensis was found to be more dominant than Echinochloa crus-galli and Ischaemum rugosum in District-II, District-III and District-IV. Pane (1995) had also reported that Leptochloa chinensis was the dominant species according to their importance value (I.V. 38 - 92) than Echinochloa crus-galli ( I.V.13 - 57).

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The other important grass was Ischaemum rugosum. The build up of Leptochloa chinensis and Ischaemum rugosum populations have been frequently observed in rice fields treated with molinate over several seasons (Ho and Zakaria, 1995). Important broadleaved weeds observed in this study in all 4 districts were Ludwigia hyssopifolia and Sphenoclea zeylanica. The gradual shift of certain broadleaved weeds was observed by Azmi and Mashhor (1995) in Kemubu, Kelantan due to changes in cultural practices. In 1989, Monochoria vaginalis, Sagittaria guyanensis, and Limnocharis flava were dominant broadleaved weeds. A similar situation prevailed in 1991. However, in 1993, Ludwigia hyssopifolia was observed to rapidly increase in abundance instead of Sagittaria guyanensis and Limnocharis flava where direct seeding was widely practice. In contrast, Tomita et al. (2003) observed that the dominance of Ludwigia hyssopifolia in Thailand was unchanged even with changes in cultural practices from transplanting to direct seeding. However, in Muda area the previously dominant broadleaved weed species Monochoria vaginalis and Sphenoclea zeylanica (Azmi et al., 1993) and Ludwigia octovulvis (Pane, 1995) were being replaced by Ludwigia hyssopifolia and Sphenoclea zeylanica was unchanged in District-I. Fimbristylis miliacea was still the most important sedge, irrespective of the shift in cultural practice from transplanting to direct seeding in all 4 districts. Tomita et al. (2003) also reported the same scenario that Fimbristylis miliacea grew in both direct seeded and transplanted fields, indicating this species was not influenced by the change from transplanting to direct seeding. Apparently, Fimbristylis miliacea would remain as the dominant weed species in direct seeded rice areas because of the tremendous size of the seed bank accumulated over years of transplanting (Azmi and Mashhor, 1996).

CONCLUSION In this study most widespread and abundant weed species with their hierarchical decreasing ranking were Oryza sativa> Leptochloa chinensis> Echinochloa crus-galli, Ischaemum rugosum> Ludwigia hyssopifolia> Fimbristylis miliacea in District-II, III and IV. In District-I Sphenoclea zeylanica was widespread species instead of Ischaemum rugosum with hierarchical order of Oryza sativa> Echinochloa crus-galli> Leptochloa chinensis> Ludwigia hyssopifolia> Fimbristylis miliacea> Sphenoclea zeylanica.

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There should now be greater concern with the apparent increase in the spread of weeds Oryza sativa complex (weedy rice), limited success in the suppression of Leptochloa chinensis, Echinochloa crus-galli and Ischaemum rugosum populations, the gradual shift in increasing importance of Ludwigia hyssopifolia in the Muda area, and the prevailing dominance of the sedge Fimbristylis miliacea despite the changes in cultural practices from transplanting to direct seeding. The movement of equipment from field to field and seeds transported by irrigation water seemed to be the main cause for the similarity in weed infestations in all districts of Muda. It is recommended that control measure should be first targeted towards grassy weeds, especially the most noxious and competitive newly spreading species Oryza sativa complex (weedy rice). Hence more indepth and surveys are needed to monitor the distribution and dominance of weeds due to inefficient or inadequate agrotechnical and cultural practices in rice cultivation.

ACKNOWLEDGEMENT This study is part of a Ph.D. research work funded by Third World Organization for Women in Science (TWOWS) Trieste, Italy and Universiti Putra Malaysia under the Intensification of Research in Priority Areas (IRPA) (No.: 01-0204-0778-PR0068/05-05 )

REFERENCES Azmi, M. 1988. Weed competition in rice production. In: Proceedings, National Seminar and Workshop on Rice field Weed Management, Penang, Malaysia. Malaysian Plant Protection Society. pp. 5. Azmi, M., Baki, B.B. and Mashhor, M. 1993. Weed communities in principal rice growing areas in Peninsular Malaysia. MARDI Report No. 165, pp.1-16. Azmi, M. 1994. Biology and control of Echinochloa crus-galli (L.) Beauv. in direct seeded rice. Ph.D. Thesis, p. 333. Universiti Sains Malaysia. Azmi, M. and Mashhor, M. 1995. Weed succession from transplanting to directseeding method in Kemubu rice area, Malaysia. Journal of Bioscience, 6(2): 143-154. Azmi, M. and Mashhor, M. 1996. Effect of continuous direct seeding on weed species diversity in Seberang Perai rice granary, Malaysia. MARDI Research Journal, 24(1): 93-105.

Azmi, M. (2002) Weed succession as affected by repeated application of the same herbicide in direct-seeded rice. Journal of Tropical Agriculture and Food Scence, 30(2): 151-161. Bernasor, P.C. and De Datta, S.K. 1983. Integration of cultural management and chemical control on weeds in broadcastseeded flooded rice. In: Proceedings of 9 th Asian Pacific Weed Science Society Conference, pp. 137-155. Bhan, V.M. 1983. Effect of hydrology, soil moisture regimes, and fertility management on weed populations and their control in rice. In: Weed Control in Rice. International Rice Research Institute. pp. 47-56. Los Banos, Laguna, Philippines. Chancellor, R.J. and Froud-Williams, R.J. 1982. A survey of grass weeds in central southern England. Weed Research, 22: 163-171. Chancellor, R.J. and Froud-Williams, R.J. 1984. A second survey of cereal weeds in central southern England. Weed Research, 24: 29-36. De Datta, S.K. 1988. Overviews of rice weed management in tropical rice. In Proceedings of National Seminar and Workshop on Rice Field Weed Management. Y.M. Lam, A.W. Cheong and M. Azmi (eds.). Penang, Malaysia. pp. 124. De Datta, S.K. 1990. Strategic weed research for relevant rice technology. In: Proceedings of the third Tropical Weed Science Conference. Kuala Lumpur, Malaysia, pp. 277-286. Elazegul, F.A.,J., Bandong, J., Estorninos, L Jonson, I. Teng, P.S., Shepard, B.M., Litsinger, J.A., Moody, K. and Hibino, H. 1990. Methodology used in the IRRI integrated pest survey. In: International Rice Research Institute. Crop loss assessment in rice. Los Banos, Laguna, Philippines. pp. 243271. Froud-Williams, R.J. and Chancellor, R.J. 1987. A survey of weeds of oilseed rape in central southern England. Weed Research, 27: 187194. Goldsmith, F.B., Harisson C.M. and Morton, A.J. 1986. Description and analysis of vegetation. In: Methods in Plant Ecology. P.D. Moore and S.B.Chapman (eds). London. Blackwell Scientific Publication. pp. 437-521. Holzner, W. 1982. Weeds as indicators. In Biology and Ecology of Weeds (Holzner W. and Numata, N. ed.), The Hague. Dr W. Junk Publ. pp. 187-190. Ho, N.K., 1984. An overview of weed problems in the Muda irrigation scheme of Malaysia. MADA Monograph No. 44. Muda Agricultural Development Authority, Alor Setar, Malaysia, pp. 97.


Ho, N.K. and Zuki, I. Md. 1988. Weed population change from transplanted to direct seeded rice in the Muda area. In: Proceeding of the National Seminar and Workshop on Rice field Weed Management, Penang, Malaysia. pp. 55-67. Ho, N.K. and Zainuddin, Z. 1995. Integrated weed management in dry-seeded rice in the Muda area, Malaysia. Paper presented at the Agricultural Extension Meeting, Muda Agricultural Development Authority (MADA) Alor Setar, Malaysia. p.14. Ho, N.K. and Zakaria, Z. 1995. Integrated weed management (IWM) on dry-seeded rice in the Muda Area, Malaysia. Paper presentation at the Agricultural Extension Meeting, 14 March, 1995. Muda agricultural Development Authority (MADA). Alor Setar. P.18. Janiya, J.D. and Moody K. 1983. Weed growth and yield of two rice crops grown in sequence in three rainfed locations in the Philippines. Philippine Agriculturist, 66: 90-101. Janiya, J.D. and Moody, K. 1989. Weed populations in transplanted and wet-seeded rice as affected by weed control method. Tropical Weed Management, 35(1): 8-11. Kuan, C.Y. Ann, L.S. Ismail, A.A., Leng, T. Fee, C.G. and Hashim, K. 1990. Crop loss by weeds in Malaysia. In: Proceeding, Third Tropical Weed Science Conference, held at Hilton Hotel, Kuala Lumpur, 4-6 December, 1990, pp. 1-21. Mabbayad, M.O., Pablico, P.P. and Moody, K. 1983. The effect of time and method of land preparation on weed populations in rice. In: Proceedings of 9th Asian-Pacific Weed Science Society Conference, pp. 357-368. Moody, K. and De Datta, S.K. 1982. Integration of weed control practices of rice in tropical Asia. In: Weed Control in Small Farms, (Soerjani, M. et al. (eds.)) BIOTROP Special Publication, No. 15, pp.34-47. Moody, K. and Drost, D.C. 1983. The role of cropping systems on weeds in rice. In: Weed control in rice. Los Banos, Laguna, Phillipines International Rice Research Institute. pp. 7488. Moody, K. 1990. Pest interaction in rice in the Philippines. In Pest Management in Rice, (Grayson, B.T., Green, M.B. and copping, L.G., ed.). New York Soc. of Chem. Industr. and Elsevier Appl. Sci. pp. 269-299. Mortimer, M., Pandey, S. and Piggin, C. 2000. Weedy rice: approaches to ecological appraisal and implications for research priorities. In: Proceedings of Wild and Weedy Rice in Rice Ecosystems in Asia – A Review

41

(ed. by Baki, B.B., Chin D.V. and Mortimer, M.) International Rice Research Institute, Los Banos, Philippines, 97-105. Pane, H. 1997. Studies on ecology and biology of red sprangletop [Leptochloa chinensis) (L.) Nees] and its management in direct seeded rice. Ph. D. Thesis. Universiti Sains Malaysia. p. 41-60. Pablico, P.P and Moody, K. 1985. A survey of lowland rice (Oryza sativa) weeds in central and southern Luzon, Philippines. Philippines Journal of Weed Science, 12: 44-55. Supaad, M.A., Suhaimi, O. and Cheong, A.W. 1991. Direct seeding practices and its implication on national productivity. Teknologi Padi, 6: 1-8. Suhaimi,O., Mohd Aris, J. and Ismail, A.B. 1987. Agroclimatic environment and productivity of major rice growing areas in Peninsular Malaysia. In: Proceedings of the National Rice Conference, 20 -22nd January, 1986, MARDI, Serdang, pp.65-85. Tomita, S., Nawata, E., Kono, Y., Nagata, Y., Noichana, C., Sributta, A. and Inamura, T. 2003. Differences in weed vegetation in response to cultivating methods and water conditions in rainfed paddy fields in northeast Thailand. Weed Biology and Management, 3: 117-127. Vaughan, D.A, Zain, A.M., Watanabe, H. and Okuno, K. 2003. Relationship between wild, weedy and cultivated rice in Malaysia. IPM activities in Malaysia. (ss.jircas.affrc.go.jp./ engpage/annualreport/1995). Watanbe, Y. and Azmi, M. 1995. Weed seed bank, longevity and dormancy in relation to weed management in rice. In: Weed management in rice production. H.R. Papusas and K.L. Heong (eds.). International Rice Research Institute, Los Banos, Laguna, Philippines. pp. 253-266. Watanabe, H., Zuki, Md. and Ho, N.K. 1997. Response of 2,4-D resistant biotype of Fimbristylis miliacea (L.) Vahl. to 2,4-D dimethylamine and its distribution in Muda plain, Peninsular Malaysia. Journal of Weed Science and Technology, 42(3): 240-249. Watson, A.K., Mabbayad, M.O., Zhang, W., Masankay-Watson, R.F., Deluna-Coutere, L.Z., Yandoc, C.B., Paulitz, T.C. and Mortimer, A.M. 1997. Progress of a biological weed control project in rice-based cropping systems in Southeast Asia. In: Proceedings of Sixteenth Asian Pacific Weed Science Society Conference, ed. Rajan, A. A Malaysian Plant Protection Society, Kuala Lumpur, Malaysia, pp. 342-344.