The Effect of Different Concentration of Glyphosate on the Growth of Coconut Seedlings

S. H. S. Senarathne,J. K. D. S. W.  Jaya,K. P. P. Premarathne 韓國雜草學會 2012 Weed&Turfgrass Science Vol.32 No.3

Coconut (Cocos nucifera L) is one of the predominant plantation crops in Sri Lankan economy which is known to have existed for over thousands of years. During the past decades coconut production had been reduced by a significant quantity. The usage of poor quality planting materials is a major reason for the low coconut production. Thus much attention needs to be paid in coconut nurseries. Weed management is a critical management practice in the nursery. Though glyphosate application is becoming popular in nurseries it can affect weeds as well as coconut seedlings growth. Therefore the effects of glyphosate were evaluated by determining the growth of shoot and root of coconut seedlings. Poly bag nursery was prepared and three treatments were used. Treatments were no glyphosate and manual weeding (T1), application of glyphosate 1.08 ai kg ha-1 at 2 monthly interval (T2) and application of glyphosate 1.44 ai kg ha-1 at 2 monthly interval (T3). Application of glyphosate at early stage of seedling growth had a no significant effect on growth parameters tested. However, the concentrations of glyphosate negatively affected numbers, volumes and dry weights of secondary, tertiary and quaternary roots at the latter stage of seedling growth. The leaf area and the height of seedling were significantly reduced by the highest concentration of glyphosate. Among the growth parameters tested, seedling girth and shoot dry weight were not affected by the application of glyphosate. These results revealed that the usage of glyphosate at both concentrations negatively affected root growth of coconut seedlings. Based on these results, the both concentration levels of glyphosate should be applied to coconut nurseries before sprouting the seed nuts.

The Effect of Different Concentration of Glyphosate on the Growth of Coconut Seedlings

Senarathne, S.H.S.,Jayaneththi, J.K.D.S.W.,Premarathne, K.P.P. The Korean Society of Weed ScienceThe Turfgrass So 2012 Weed&Turfgrass Science Vol.32 No.3

Coconut (Cocos nucifera L) is one of the predominant plantation crops in Sri Lankan economy which is known to have existed for over thousands of years. During the past decades coconut production had been reduced by a significant quantity. The usage of poor quality planting materials is a major reason for the low coconut production. Thus much attention needs to be paid in coconut nurseries. Weed management is a critical management practice in the nursery. Though glyphosate application is becoming popular in nurseries it can affect weeds as well as coconut seedlings growth. Therefore the effects of glyphosate were evaluated by determining the growth of shoot and root of coconut seedlings. Poly bag nursery was prepared and three treatments were used. Treatments were no glyphosate and manual weeding ($T_1$), application of glyphosate 1.08 ai kg $ha^{-1}$ at 2 monthly interval ($T_2$) and application of glyphosate 1.44 ai kg $ha^{-1}$ at 2 monthly interval ($T_3$). Application of glyphosate at early stage of seedling growth had a no significant effect on growth parameters tested. However, the concentrations of glyphosate negatively affected numbers, volumes and dry weights of secondary, tertiary and quaternary roots at the latter stage of seedling growth. The leaf area and the height of seedling were significantly reduced by the highest concentration of glyphosate. Among the growth parameters tested, seedling girth and shoot dry weight were not affected by the application of glyphosate. These results revealed that the usage of glyphosate at both concentrations negatively affected root growth of coconut seedlings. Based on these results, the both concentration levels of glyphosate should be applied to coconut nurseries before sprouting the seed nuts.

The Allelopathic Effects of Lantana camara on Seed Germination and Growth of Selected Bioassay Species

Senarathne, S. H. S,R. D. V. Fernanado,U. R. Sangakkara 韓國雜草學會 2011 Weed&Turfgrass Science Vol.31 No.3

The allelopathic effects of Lantana camara L. (Family:Verbenaceae) on germination and seedling establishment of some agricultural crops and weed species have been identified. Aqueous extracts of dry leaves and contaminated soil where L. camara is grown were used to verify allelopathic effect on seed germination of five bioassay species; Raphanus sativas, Capsicum annum, Lycopersicum esculantem, Crotalaria juncia and Chromoleana odorata. Fifty seeds from each bioassay species were placed in a petri dish containing leaf extracts or contaminated soil, and seed germination were examined after 3 days. The plant house experiments were carried out to evaluate the impact of L. camara contaminated soil and leaf debris using L. esculantem as the indicator plant. Seed germination of L. esculentem, C. junica and Capsicum annum was significantly inhibited by L. camara contaminated soil. However, the degree of inhibition varied among the bioassay species. The aqueous extract of dry leaves of L. camara was highly phytotoxic and it significantly reduced seed germination of all bioassay species. There was a decline in plant height, leaf area and shoot dry weight of tomato only in early growth stages when grown in L. camara contaminated soils. However, incorporation of leaf debris into soil affected the vegetative growth of tomato in early stages when the leaf debris concentration was increased. Growth recovered at the latter part of the life cycle. On the basis of these results it can be concluded that the allelochemicals in L. camara contaminated soils are harmful to the seed germination of crop species. The adverse effect was present only during the early growth stages and it did not suppress the latter part of the plant growth. These responses are attributed to allelopathic effects which need confirmation under field conditions.

Germination Characteristic of Rhizomes of Major Monocotyledonous Weeds in Coconut Plantations of Sri Lanka

Senarathne, S.H.S.,Bandara, D.M.B.M.,Sangakkara, U.R. The Korean Society of Weed ScienceThe Turfgrass So 2012 Weed&Turfgrass Science Vol.32 No.3

Panicum maximum, Panicum repens, Imperata cylindrica, Pennisetum polystachion and Cyperus rotundus are five rhizomatous grass weeds that exist and are problematic in the coconut lands of Sri Lanka. Rhizomatous weeds are the most difficult to control because of their vegetative reproduction by underground propagules. Therefore chemical and biological techniques have failed to control these weeds to acceptable levels. Experiments were conducted to investigate the impact of depth of burial, duration of sun drying or duration of air drying rhizomes of the selected weed species on germination. Depth of burial reduced germination of all species. Burying rhizomes at depths less than 10 cm inhibited germination of P. maximum and P. polystachion. Burying depths below 30~40 cm inhibited germination of all species. Sun drying or air drying rhizomes for durations less than 5 days inhibited germination of P. maximum and P. polystachion. Germinations of all species were inhibited by sun drying rhizomes for 15 days or air drying rhizomes for 20 days. Sun drying of rhizomes of all species for five days reduced the moisture content to a greater extent than air drying. The results indicated that burying rhizomes at the depthsbelow 30~40 cm, sun drying rhizomes for durations beyond 15 days or air drying rhizomes for durations beyond 20 days would be effective in controlling germination of these species. The investigations of the experiments also suggest that keeping rhizomes on the soil surface without burying, sun drying rhizomes or air drying rhizomes for durations of 5~15 days would produce weak plants.

Influence of Moisture, pH, Depth of Burial and Submerged Conditions on Seed Germination and Seedling Emergence of Major Weed Species in Coconut Plantations of Sri Lanka

S. H. S. Senarathne,U. R. Sangakkara 韓國雜草學會 2010 Weed&Turfgrass Science Vol.30 No.3

The laboratory and green house studies evaluated the effect of three different environmental factors on the seed germination, seedling emergence and survival of four major weed species in coconut plantations, Mimosa pudica, Ureana lobata, Panicum maximum and Pennisetum polystachyon. Germination percentage of all the weed species was significantly reduced with increasing soil moisture stress, no germination was observed at -0.9 ㎫. Germination of both grass seeds ranged from 8% to 25% and 10% to 45% a moisture stress decreased from -0.4 ㎫ to 0 ㎫ respectively. In contrast, seeds of M. pudica, and U. lobata were moderately tolerant to soil moisture stress and best adapted to moist environment. All the weed species seeds germinated over a wide range of soil pH values with the highest germination occurring at pH 6. In all the species, seedling emergence was declined rapidly with increasing depth with the exception of U. lobata. Seedling emergence significantly declined when the duration of flooding was three days or longer in dicotyledonous weed species and two days or longer in monocotyledonous weeds. This study illustrates the adaptability of these weeds to different environmental conditions which would enable the development of management strategies to reduce their populations below economic threshold levels in coconut plantations.

Germination Characteristic of Rhizomes of Major Monocotyledonous Weeds in Coconut Plantations of Sri Lanka

S.H.S. Senarathne,D. M .B. M. Bandara,U.R. Sangakkara 韓國雜草學會 2012 Weed&Turfgrass Science Vol.32 No.3

Panicum maximum, Panicum repens, Imperata cylindrica, Pennisetum polystachion and Cyperus rotundus are five rhizomatous grass weeds that exist and are problematic in the coconut lands of Sri Lanka. Rhizomatous weeds are the most difficult to control because of their vegetative reproduction by underground propagules. Therefore chemical and biological techniques have failed to control these weeds to acceptable levels. Experiments were conducted to investigate the impact of depth of burial, duration of sun drying or duration of air drying rhizomes of the selected weed species on germination. Depth of burial reduced germination of all species. Burying rhizomes at depths less than 10 cm inhibited germination of P. maximum and P. polystachion. Burying depths below 30~40 cm inhibited germination of all species. Sun drying or air drying rhizomes for durations less than 5 days inhibited germination of P. maximum and P. polystachion. Germinations of all species were inhibited by sun drying rhizomes for 15 days or air drying rhizomes for 20 days. Sun drying of rhizomes of all species for five days reduced the moisture content to a greater extent than air drying. The results indicated that burying rhizomes at the depthsbelow 30~40 cm, sun drying rhizomes for durations beyond 15 days or air drying rhizomes for durations beyond 20 days would be effective in controlling germination of these species. The investigations of the experiments also suggest that keeping rhizomes on the soil surface without burying, sun drying rhizomes or air drying rhizomes for durations of 5~15 days would produce weak plants.

Use of Different Herbicides on Weed Management in Coconut Nurseries in the Intermediate Zone of Sri Lanka

S. H. S SENARATHNE,K. C. P. PERERA 韓國雜草學會 2009 Weed&Turfgrass Science Vol.29 No.2

Effect of three different herbicides and manual weeding on the growth of coconut seedlings was evaluated to determine the most economical and effective herbicide for controlling weeds in coconut nurseries in the intermediate zone of Sri Lanka. The treatments comprised; manual weeding (T₁), application of glyphosate at 1.44 kg ai ha-1 (T₂), application of diuron at 3.20 kg ai ha-1 (T₃) and application of oxyflurofen at 0.27 kg ai ha-1 (T₄). All treatments were applied at three monthly intervals. According to the results, treatments T₂ and T₃ significantly reduced the weed biomass compared to those of other treatments and the weed seedlings emergence density was very low in diuron applied plots. The growth of coconut seedlings (in terms of girth) increased significantly (P-1 resulted in reduced growth of seedlings at the latter part of the experiment. The highest growth rate of coconut seedlings (girth) was observed in T₃ plots. The most effective and economically viable herbicides were the application of glyphosate at 1..44 kg ai ha-1 and diuron at 3.20 kg ai ha-1 for controlling weeds in coconut nurseries.

Effect of different weed management systems on the weed populations, and seedbank composition and distribution in tropical coconut plantations

Sumith H. S. Senarathne,Ravi U. Sangakkara 한국잡초학회 2009 Weed Biology and Management Vol.9 No.3