Browsing by Author "Premathilake, K.G."

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    Analysis of Pesticide Residues in Fruits and Vegetables exported to the European Union and determining the effect of Chlorine Treatment on Diazinon Residues
    (Uva Wellassa University of Sri Lanka, 2018) Mallikaarachchi, M.A.S. K.; Magamage, M.C.; Premathilake, K.G.; Weerawansha, A.N.R.
    Presence of pesticide residues in agricultural commodities can cause acute and chronic toxicities on humans.The objective of this study was to develop a monitoring programme to regulate the pesticide usage of farmers and to determine the effect of chlorine treatment on diazinon residues of tomato and bean samples. Two surveys were conducted to identify the malpractices of the farmers and exporters who cultivate and process the commodities, which are exported to the EU. A total of 98 samples of fresh fruits and vegetables were analysed for the presence of 66 active ingredients of pesticides. The quick easy cheap effective rugged and safe multi-residue extraction method was followed, using gas chromatography mass spectrometry. There were no malpractices were identified at farmer level while three malpractices were identified at exporter level. Analytical results revealed that only 26% of the samples were positive for pesticide residues. Pesticide residues above the European Union Maximum Residue Limit (MRL) were detected in 65% of samples among the contaminated. Multiple residues (2-3) were present in 11% of contaminated samples. Eleven pesticides were detected, of which 7 were insecticides, 4 were fungicides and no weedicides. Mostly detected active ingredients were profenophos and etofenphox, both of which were insecticides and carbendezim, a fungicide. The chlorine treatment had a significant effect on reduction of Diazinon residues in tomato (p = 0.024) and bean (p = 0.005) samples. The results confirmed the presence of pesticide residues in fruits and vegetables exported to the EU. Chlorine treatment at 150 ppm dosage could effectively reduce the residues of diazinon in tomato and beans.
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    Evaluation of the Physiochemical Stability of Different Formulations of Diazinon 50 within Its Shelf-life
    (Uva Wellassa University of Sri Lanka, 2016) Kularatne, H.A.S.P.; Premathilake, K.G.; Weerewansha, A.N.R.; Magamage, C.
    Pesticide formulations can undergo chemical and physical changes on storage. The physiochemical stability of the product has been of exalted concern to the efficacy and safe use of the product within its shelf life. A laboratory evaluation to determine the physiochemical stability of Diazinon emulsifiable concentrate, emulsion oil in water and granule formulations within its shelf-life was conducted. The physical and chemical parameters of the respective formulations were assessed as a function of time at ambient temperature and after storage at 54 °C for 14 days. Analysis was performed as per the Collaborative International Pesticides Analytical Council protocols and in accordance with Food and Agriculture Organization and World Health Organization specifications. The results revealed physiochemical instability in EC formulations was affected by time units and temperature. A marked variation in pH and active ingredient were apparent in EC formulations of 12-18 months old and >24 month old obtained from local manufacturers. A mean active ingredient of 429.34 at mean pH 3.3 was registered with 12-18 month old sample and a mean active ingredient of 249.8 at mean pH 2.2 was registered with >24 month old sample. EW formulations comply with specifications in pH, density, specific gravity and emulsion stability in spite of the slight differences shown. Wettability and persistent foaming of granule samples were in conformity with the WHO specifications. Granule sample of 12-18 months old recorded a decrease in pH recording a mean value of 6.1. Despite the EC samples of time 12-18 months old and >24 month old, stability of the active ingredient content evaluated for all 3 Diazinon formulations used in study were in agreement with the specifications with time units within its shelf-life. However significant difference in active ingredient content was recorded in all formulations used in the study after storage at 54 °C which shows light for the formation of toxic impurities. Keywords: Diazinon, Physiochemical stability, EC formulation, EW formulation, GR formulation
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    Germination Characteristics of Rhizomes of Panicum maximum in Coconut Plantations of Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2018) Augustin, A.M.; Senarathne, S.H.S.; Premathilake, K.G.; Herath, H.M.S.K.
    Panicum maximum is a major weed in the coconut lands and many of the bare lands. Being an invasive and aggressive weed, other than high seed production capacity, germination of rhizomes has a major role for its continuity as a perennial weed. If germination is controlled, it would ultimately result in growth suppression and control of the weed for some extent. Experiment was therefore conducted to investigate the impact of air drying of rhizomes of P. maximum on reduction of moisture, total carbohydrate percentage and finally the germination at the CRI, Lunuwila, Sri Lanka. A bulk of uniformly grown plants of P.maximum was uprooted from a coconut land and grouped into 8 treatments based on three factors such as presence/absence of soil with roots, presence/absence of leaves, split/unsplit bush condition. Rhizomes were air dried for 0 to 12 days at 3 days interval in a plant house. Air drying of rhizomes for more than 3 days reduced the moisture content, total carbohydrates and germination of rhizomes. Initial moisture content of 75.4 % reduced to the lowest of 6.4% when drying for 12 days in P.maximum without soil, with leaves treatments. Initial carbohydrate content also reduced from 0.17% to 0.03% when drying for 12 days in P. maximum without soil, without leaves treatments. Germination was totally inhibited when air drying for more than 9 days in all treatments and further P.maximum without soil, with leaves treatments recorded 16 - 20% germination. Most effective agronomic practice to control P.maximum was the removal of the soil attached to the root system after uprooting and laying for air drying for 6-9 days, where soil is no in contact with roots.
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    Impact of Socio-economic Status of Tea Smallholders on the Production of Tea Lands in Passara Tea Inspector (TI) Range
    (Uva Wellassa University of Sri Lanka, 2018) Yapa, Y.M.S.K.B.; Premathilake, K.G.; Dharmadasa, R.A.P.I.S.; Thalagoda, U.
    Contribution of smallholders to the Sri Lankan tea sector is higher than the plantation sector. Knowing the socio-economic status helps find the strategies for improving smallholder's living conditions and their production. This study was undertaken to assess the impact of socio-economic status of tea small holders in the Passara tea inspector range on the production of their tea lands and also to identify the constraints faced by them in socio-economic upliftment. Data were collected from randomly selected 150 smallholders who are registered in five smallholding development societies out of 15 societies in Passara area by using a structured questionnaire through a face to face interview. Descriptive statistics and regression techniques were used to analyze the data. Simple linear regression results revealed that gender, education level, farming experience of the smallholder, monthly fertilizer cost and farm size positively affect the production while marital status of the smallholder negatively affect the production. Major constraints faced by the smallholders are poor infrastructure facilities, high cost for children's education, high cost of field operations, and pest and disease attack on tea cultivation. Proper extension services and field training programmes are suggested to offer them to gain their knowledge and experience on proper field practices. Continuously providing sufficient amount of fertilizer allowance and supplying of credit facilities are also needed. Infrastructure facilities should be developed in the Passara area. Various social organizations and societies should come forward to improve the socio-economic status of the small scale tea growers.
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    Investigating the Association between Vesicular Arbuscular Mycorrhiza (VAM) and Connnelina benghalensis
    (Uva Wellassa University of Sri Lanka, 2018) Gunasena, H.M.P.M.; Premathilake, K.G.; Balasooriya, A.
    A study was conducted to investigate the presence of an association between the Vesicular Arbuscular Mycorrhiza (VAM) and Commelina benghalensis. The effect of C. benghalensis as a weed was also studied as a specific objective. A pot experiment was carried out using single nodal stem cuttings of C. benghalensis and chili plants applied in 4 treatments, i.e. 3 stem cuttings + 2 chili plants (Treatment 1), 6 stem cuttings + 2 chili plants (Treatment 2), 6 stem cuttings alone (Treatment 3) and 2 chili plants alone (Treatment 4). Experiment was carried in a Completely Randomized Design with 10 replicates. As an indicator plant, chili seeds were sown after 3 days of planting weed cuttings and thinned out upto two plants per pot. Growth measurements of chili (height) and C. benghalensis (creeper length) were measured at fortnight intervals. After 10 weeks of planting cuttings, fresh and dry weights of chili and weed were measured, soil nutrient analysis for Carbon, Nitrogen and Phosphorus for each treatment was done, soil VAM spore counts were taken and root colonization percentages of VAM were calculated from each treatment. Root colonization percentages and the spore counts gave no any significant difference among treatments having C. benghalensis. Root colonization percentage by VAM ranged from 50-55% at 10 weeks after planting and the soil VAM spore count ranged 170-185 per 100 g of soil. Soil phosphorous level was significantly higher in pots with C. benghalensis due to Phosphorous solubilization. Therefore, the limiting factors for plant growth seemed to be some other nutrients or factors, rather than Phosphorus. Longest creeper length, creeper fresh and dry weight were observed in treatment 3 and significantly lower in treatment 2. Height, and fresh and dry weight of chili were significantly lower in treatment 2 and treatment 3 compared to treatment 4.The study concluded that there is an association between VAM and C. benghalensis and although there is a competition between the weed and the crop there are some favorable effects particularly due to Phosphorus solubilization.
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    Investigation of Potential Allelopathic Shade Tree Species for Controlling Weeds in Tea Lands
    (Uva Wellassa University of Sri Lanka, 2019) Pathinayake, P.W.; Ranawana, S.R.W.M.C.J.K.; Kaliyadasa, P.E.; Premathilake, K.G.
    Identification of eco-friendly organic weedicides has become a need of the day. There are evidences on some allelochemicals in mature leaves of some shade trees. A study was undertaken to evaluate the bio efficacy of different concentration of mature leaf extracts of shade trees (Gliricidia sepium, Calliandra calothrysus, Acacia pruinosa, Erythrina lithosperma, Gravillea robusta) and the most effective extraction technique. This research was conducted as two studies (bioassay and pot study). Mature leaves of selected shade tree species were first oven dried and milled. Leaf extracts were prepared each in four concentrations (20, 40, 60, 80% w/v) using cold and hot distilled water extraction methods. A bioassay conducted using lettuce seeds as the indicator plant. Distilled water was used as the control. Bioassay results revealed no significant difference between cold and hot distilled water extraction methods (p>0.05). G. sepium at 80% recorded the lowest germination percentage (17.8%) and lowest germination index (0.4) followed by G. robusta at 80% (21.9%, 0.5), E. lithosperma at 80% (29.5%, 0.6), G. sepium at 60% (31.8%, 0.7), G. robusta at 60% (39.8%, 0.9) and E. lithosperma at 60% (51.0%, 1.1), respectively. Lowest hypocotyl (3.0 mm) and radical lengths (1.8 mm) and lowest seedling vigor index (0.1) was recorded in G. sepium at 80%. Based on those results, most phytotoxic extracts (G. sepium, G. robusta and E. lithosperma each at two different concentrations i.e. 60, and 80% w/v) were selected and further tested on three weed species (Cleoma aspera, Bidens pilosa and Ageratum conyzoides) planted on pots in three replicates. According to the pot study G. sepium at 80% recorded significantly highest dead weed count (C. aspera, 100%; B. pilosa, 66.6%; A. conyzoides, 66.6%) 14 days after applications. Thus, G. sepium at 80% can potentially be used to control succulent broad leaf weeds in tea lands. Further investigations are required under field conditions.
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    Investigation on Durable Plant Materials as Alternative Sources of Mulch in Tea New Clearings in the Upcountry Intermediate Zone
    (Uva Wellassa University of Sri Lanka, 2020) Kumudika, W.A.H.; Premathilake, K.G.; Leelarathne, C.
    Mulching as a cultural technique is an eco-friendly practice to manage weeds. Hence, a field experiment was conducted to investigate the potential use of different plant materials as mulches in a tea new clearing at Ury estate, Passara, from September to December 2019. Tertiary branches of Acacia mangium (Acacia), Cassia spectabilis (Kahakona), Grevillea robusta (Sabukku) with leaves, and Megathyrsus maximus (Guinea grass) were used as treatments and Cymbopogon confertiflorus (Mana grass) was used as the ‘Control’. Each mulch was spread on randomly selected tea plots each sized 14.4 m2 at a rate of 1 kg dry matter m-2 and replicated three times. The rate of decomposition of each material was assessed in terms of ground exposure percentage and weight reduction in litter bags filled with each mulch material at fortnight intervals. Weed density and weed dry weight were measured at 2 and 4 weeks intervals, respectively. Plant growth parameters were measured before and after 12 weeks mulching. Soil moisture and soil carbon content were measured. A bioassay was also conducted for any allelopathic effect of mulch materials. Half-life (time taken for 50% ground exposure) as 8.1, 9.2, 10.0, 10.3, 12.0 weeks was recorded for Kahakona, Acacia, Guinea grass, Mana grass, and Sabukku respectively. Whilst, the same was recorded as 100%, 98%, 88%, 68%, and 50% respectively 12 weeks after mulching. The weight of Sabukku mulch was significantly higher (p<0.05) than other materials. Weed density and weed dry weight were significantly lower with Sabukku. Tea growth was not significantly affected by any treatment. Guinea grass and Sabukku were found to be increased the soil carbon level while high moisture content was recorded underneath the mulch of Mana and Sabukku. Sabukku was found to be more durable and could effectively suppress weed growth. Guinea grass and Mana grass showed some comparable performances. Sabukku and Guinea grass can be used as alternatives mulches for Mana grass Keywords: Allelopathic effect, Decomposition of mulch materials, Suppression, Tea, Weed growth.
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    Perception of Tea Small Holders in Badulla District in Adopting Mix Crop Cultivation
    (Uva Wellassa University of Sri Lanka, 2012) Swarnamali, M.A.N.; Premathilake, K.G.; Gunathilaka, R.P.D.; Jayasinghe, H,A.S.L.
    Tea is a humid loving tree species, the growth of tea is negatively affected by strong light and high temperature (Ekanayake, 2003). There is a potential to supplement the shade with other tree species of economically important as the method of mix crop cultivation with tea (Jayasinghe, 1982). It is important to maintain adequate shade as well as to increase the unit land productivity. It was aimed to study the factors that affect the willingness of tea smallholders for adopting mix crop cultivation in tea small holdings in Badulla district.
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    Value Addition to Off Grade Tea by Incorporating Tea Aroma
    (Uva Wellassa University of Sri Lanka, 2016) Ellepola, V.P.; Premathilake, K.G.; De Silva, P.D.P.M.P.; Chitty, A.
    Considerable amount of volatile compounds which formed up to fermentation process are lost during drying. An experiment was conducted to study how to make use of, amount of volatiles formed during fermentation process of tea to enhance the organoleptic attributes of off grade tea. Experiment was conducted at Rozella tea factory, Watawala. After extracting aromatic volatiles from fermented tea dhools, concentration of the extract, was enhanced. The developed treatment was then used to add value to off grade tea and sensory evaluation was conducted. Then moisture content of the developed teas were recorded. Off grade tea incorporated with 1% of non-concentrated volatile sample and, 0.5 % of concentrated volatile sample were identified as the best treatments. Treatments had a significant impact on the development of aroma, flavour and quality traits. Hence, the study proves that resupplying of volatile compounds to off grade tea is found to be a good approach to add value to offgrade tea. Keywords: Tea Aroma, Tea off grades, Volatile compounds, Value addition