RISK ASSESSMENT OF PESTICIDE CONTAMINATION POTENTIALS IN EMBILlPITlYA AREA

Embilipitiya is a highly agricultural area, which has consumed a remarkable amount ofagrochemicals in last two decades. Hence pesticide movement level studies are necessaryto prevent the contamination of soil and water by these pesticides.Pesticides Impact Ranking Index (pIRI) is a simple computation model, which can beused for ranking pesticides according to their leaching ability and toxicity levels. Itrequires soil and climatic parameters. chemical and application information of pesticides,etc. The risk levels are indicated as very low, low, medium, high, very high andextremely high according to their leaching and toxicity conditionsThe modeling using PIRI was carried out to rank the most widely used three pesticides,3,4 DPA, Carbfuran and MCPA, for 14 different soil series present in Embilipitiya area.The risk level frequencies were calculated for each pesticide. For 8 soil series high riskleaching potential was obtained. Carbofuran and Walawa series has extremely highleaching potential than others. In comparison, MCPA has a medium risk potential for 10soil series. 3,4 DPA has a very low leaching potential for all soils.Toxicity levels obtained for most of the soil series are low except for Thimbolketiya andWalawa soil series. They have high and medium toxicity levels respectively forcarbofuran. Hence the risk level of carbofuran is very high, MCPA is medium and 3,4DPA is low in different soils present in Embilipitiya area and therefore the usage ofCarbofuran needs to be controlled. In pesticide usage and selection, extra care andawareness procedures are necessary to prevent ground water contamination in future

Assessment of the impact of diuron to water bodies in the Walawa area

Use of pesticides has significantly increased global food production and it is indispensable in modernagriculture to control weeds, insects, other pests and diseases. As the population increases the use ofpesticides also increases. The impact of these pesticides to the environment is not well understood forSri Lankan conditions Hence the sorption pattern of a non ionic pesticide, diuron {3-(3,4-dichlorophenyl)-l, l-dimethylurea; C9H IICI,KO} which is used as a herbicide to control weeds andmosses mainly in sugarcane, was studIed for-14 soil series in the right bank of the Walawa basin in SriLanka.Information was collected from fanners in Walawa areas on crops, historical cropping patterns, typeof pesticides used, pesticides handling knowledge etc. The survey revealed that pesticides use ismalpracticed by fanners. The distribution of crop types in the area during last three years shows thatPaddy, which is scattered through out the area, is the most prominent crop. The average area underpaddy cultivation is approximately 9800 ha. Banana was the second highest grown crop that is inabout 4200 ha. Sugarcane, which covers about 2500 ha, is the prominent monoculture in the Walawabasin.Adsorption of di uron to the collected surface (0-1 Ocrn) soi Is of the 14 soi I series in the Wa lawa basinwere measured using High Performance Liquid Chromatographic method. The Moraketiya seriesshowed the highest sorption among them. It also gives the highest Kd value of the selected soils andSiyambala series exhibited the lowest adsorption and Kd. The organic carbon content was highest inKachigalara series and it was lowest in the Walawa series. The measured Kd values were used topredict the risk of this pesticide to ground and surface water in the Walawa area using a simplemanagement model called Pesticide Impact Rating Index, PIRI which resulted a moderate risk forthe contamination of water bodies in the area.

Intercropping Agarwood Producing Species with Rubber for Sustaining Income

Sri Lankan rubber industry contributes to country’s economy in significant manner. Anyhow the natural rubber industry has now faced a threat due to the low price. As a solution, financially profitable other species can be intercropped with rubber to maintain sustainable income of the growers. Since agarwood has a very high demand and value in perfume and incense industry, it is worth to assess the feasibility of growing this crop with rubber. Therefore, the current study was conducted for the first time to test the potential of growing three agarwood producing species with young rubber under two intercropping systems, of which rubber is grown as a single row with 12 m and double row with 18 m spacing. The field trial was established using Aquilaria crassna, A. subintegra and the native species Gyrinops walla of family Thymalaeaceae in 2 ha land belongs Rubber Research Institute, Agalawatte in low country wet zone. A. crassna and A. subintegra seeds were imported from Vietnam and Thailand respectively while G. walla seeds were locally collected. All seeds were germinated in a nursery to raise seedlings. Then, one and three rows of agarwood species were planted at 3 m distance between rubber in single and double row systems, respectively.Tree height and stem diameter (30 cm above the ground) were measured at monthly intervals for all agarwood species (152 trees) while those of rubber (174 trees) were measured at six months and two months intervals respectively. Data collected for 4 years were analysed by one-way ANOVA and Student’s t-test. According to the results, G. walla recorded significantly lower height(F=168.58; p=0.000) and diameter (F=77.49; p=0.000) compared to both Aquilaria species in two selected intercropping systems. However, neither its height nor diameter was significantly different between two planting systems of rubber. Only A. subintegra in double row system was significantly taller than A. subintegra in single row and A. crassna in double row. Further diameter was notsignificantly different between Aquilaria species or planting system. However, the highest average tree height and stem diameter were recorded by A. subintegra in double row system and A. crassna in single row system respectively. Though diameter of rubber plants was not significantly different in two intercropping systems (t=-1.73; p=0.085), height in single row system was significantly taller (t=-3.71; p=0.000). The findings concluded that the growth performance of G. walla, the native species is comparatively lower than that of both Aquilaria species. Further, A. crassna and A. subintegra showed better height growth performances in single row and double row systems respectively. Keywords: Agarwood rubber intercropping, Aquilaria species, Gyrinops walla, Single row, Double row syste

Effect of Time of Tapping on Latex Yield of Rubber (Hevea brasiliensis) in Kalutara and Moneragala Districts of Sri Lanka

Low productivity is one of the major concerns in rubber plantations and therefore, efforts should be made to exploit the maximum potential yield from a rubber tree sustainably. The exploitation of latex (tapping), which is the most important operation in rubber crop and plantations, is normally done in the morning (around 06:00-08:30) in traditional rubber growing areas in Wet and Intermediate Zones and around 05:00-07:30 in the nontraditional areas in Intermediate Zone. Some smallholders, planters and other people/groups believe or suggest that night or early morning tapping could increase the latex yield in rubber trees. Therefore, this study was aimed at exploring the effect of time of taping on the latex yield of H. brasiliensis. Rubber trees of clone RRIC 121 were used with a plot size of 15 trees and six treatments to represent times of tapping [03:00, 04:00, 05:00, 06:00 (control), 07:00 and 08:00)] at d2 frequency at Galewatta division of the Rubber Research Institute, Agalawatta, Kalutara District and 02:00, 03:00, 04:00, 05:00 (control), 06:00 and 07:00 at a smallholder field, Yudaganawa, Moneragala District for one year. Weather and latex volume data were recorded and total crop and g/t/t (gram/tree/tapping) were calculated/estimated. No significant differences were recorded for the mean total crop and g/t/t values for the trees tapped at different time intervals in both Kalutara and Moneragala districts. Models were fit to estimate the crops that could be obtained at different time durations using these data. Accordingly, a 0.04% increase in the total crop was estimated for trees tapped during 5:00-7:30 when compared to those tapped during 06:00-08:30 in the Kalutara District. Conversely, 1.6%, 3.3%, and 5.1% increase in yield were recorded in trees tapped during 04:00- 06:30, 03:00-05:30 and 02:00-04:30 respectively when compared to those tapped during 05:00-07:30. Therefore, night/early morning tapping may not be an effective or a practical strategy/solution to increase the productivity in rubber plantations in Kalutara District, while tapping during 02:00-04:00 in Moneragala District may contribute to an increase in latex crop upto around 5%. Large-scale assessments are required for further confirmation of these results. Keywords: Hevea brasiliensis, Latex, Morning, Rubber, Tappin

FATE OF CARBOFURAN IN SELECTED SOILS OF SRI LANKA

Carbofuran (2,3 dihydro 2,2 dimethyl 7 benzofuranyl methyl carbamate) isthe most popular pesticide used in Sri Lanka. The fate, degradation anddissipation, of carbofuran was determined in four soil groups in Sri Lanka inorder to study the persistence of pesticide in soils after application.Red yellow podzolic soils (Nuwara Eliya), Alluvials (Pugoda) and Regosols(Kalpitiya and Negombo) types were selected for the experiment.For the degradation analysis, 10 g of each soil was incubated under 70% ofmaximum water holding capacity and 28 0 C of temperature at 13 hours lightand 11 hours dark conditions. 0.05 DCi of 14Cring labelled carbofuran (98%of chemical purity) was added to each soil sample and incubated in the aboveconditions. Liberated CO2 collected to an alkaline solution was analyzed byusing Liquid Scintillation Counter after 0, 1,3,5, 7, 14,28,56,90 days.For adsorption studies, 5 g of soil mixed with Ippm pesticide solution wasshaken for 16 hours in the room temperature. The supemant collected aftercentrifuging was analysed using High Performance Liquid Chromatographhaving 18C Apollo column.Carbofuran mineralization percentage was below 7.5% in all soils after 10days but a significant different showed in Kalpitiya regosols, which had arapid mineralization rate than other three soils. After 20 days mineralizationin Kalpitiya was 12.5% and in Pugoda it was 7.5%. After 90 days Kalpitiyaregosols showed over 60% of mineralization and in other three soils it wasbelow 50%. During 90 days incubation period only 10% mineralization wasshowed in Nuwara Eliya red yellow podzolic soils.In the adsorption study K, value obtained were 1.64 for Nuwara Eliya, 0.63for Kalpitiya, 0.2 for Pugoda and 0.11 for Negombo. Hence Nuwara Eliyahas the highest adsorption rate and Negombo exhibited the lowest.Nuwara Eliya has the highest organic matter among the selected soils andpesticide sorption can be expected to be the highest to Nuwara Eliya soils.The microbial degradation is expected to be high in soils having high organicmatter but the degradation rate was highest in sandy soils in Kalpitiya. Henceit can be seen that chemical and other degradation is higher than microbialdegradation of pesticides in soils in Sri Lankan conditions