Biologi dan kawalan echinochloa crus-galli (l.) beauv. dalam tanaman padi tabur terus

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Date
1994
Authors
Man, Azmi
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Abstract
Field surveys conducted in the granary areas of Peninsular Malaysia identified 16 spesies of grasses, 20 sedges, 35 broadleaved weeds and 7 aquatic weeds. Eight species were common to a 11 rice granaries of which E. crus-ga 7 7 i was the dominant weed. Detai 1 ed studies were conducted from 1989 to 1993 at MARDI Rice Research Centre, Seberang Perai including varietal identification of Echinoch7oa crusga77i and its life cycle, seed longevity, competition at various densities of this weed against direct seeded rice (DSRL critical period of weed competition, influence of rice variety, time of flooding and control methods. Echinoch7oa crus-ga77i was the dominant weed for six consecutive seasons of DSR in Seberang Perai. The studies in Kemubu, Kelantan revealed that £. crus-ga77i was pronounced after DSR was adopted. Ech i noch 7 oa crus-ga 7 7 i var. formosensis has longer seed longevity than var. crus- • ga77i. Variety crus-ga77i also showed drastic reduction in germination percentages in the rice field (with exception 2nd season which had 6. 4% germination) with 2. 94% (1st season) to 0.02% (6th season). Variety formosensis exhibited a similar trend in germination percentages from 7. 33% (1st season) to 0. 08% (6th season). Most of the seeds germinated during the first three weeks after sowing of rice. Survival test showed that after six seasons, all var. crus-ga 7 7 i seeds were not vi ab 1 e wh i 1 e about 7% of buried seeds of var. formosensis survived. Echinoch7oa crus-ga77i at different densities vary in their competitive ability with rice. Competition was more intense at high densities than at low densities. Only 10 plants/m2 were required to cause significant yield reductions of about 18.7% and 19.9% (i.e. 1 t/ha) for main season 1988/89 and off season 1989 respectively. Negative relationships between panicle;m2 and rice yield and dry weight and rice yield were obtained. A rectangular hyperbo 1 a re 1 at i onsh i p was estab 1 i shed when DSR competed at high densities of E. crus-ga77i. Economic thresholds of this weed was estimated at 1-3 pl ants;m2 . Critical period of competition between E. crus-ga77i with rice, and mixed weeds with rice in main season 1988/89 and off season 1989 respectively are at 15 to 30 DAS. Further, verifications of critical period for weed control in DSR were also carried out. Twelve rice varieties with different plant types and maturation periods were tested in main season 1989/90 under two weed control regimes, weed free at cri t i ca 1 stage and weed competition t i 11 harvest. Weed control at critical period significantly reduced weeds regrowth at 60 DAS. Yield increase in the range of 22.15 - 66. 51% was recorded. Under fu 11-season weed competition, Bahagia (tall plant with droopy leaves) was tolerant to weed competition with a lower improvement in yield production (22%). Studies showed that early flooding in off season 1990 at three and six DAS reduced the problem of E. crus-ga 7 7 i infestation. However, crop stands were thin and weak with reduced number of productive tillers. Delayed flooding espec i a 11 y after 15 DAS enhanced serious infestation of various weeds resulting in high yield loss. However, delayed flooding improved crop anchorage and weed free condition at cri t i ca 1 period, enhanced t i 11 er production and higher yields. Several methods of weed control were tested in off season 1990 and main season 1990/91 in order to suppress weeds at the critical period. Among treatments that gave si gni fi cant yield increase were manual weeding at 15 and 30 DAS, bensulfuron applied at 10 DAS followed by manual weeding at 30 DAS, pretilachlor sprayed at 4 DAS followed by manual weeding at 30 DAS and combination of molinate + bensulfuron applied at 10 DAS. Delaying the manual weeding at 30 DAS could cause physical injury to crop.
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Echinochloa crus-galli , Padi tabur terus
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