Dry Rubber Content Of Latex Research Articles

Effectiveness of a locally developed ethephon formulation on yield and related latex physiological factors of <em>Hevea brasiliensis</em>

Ethephon is an essential agrochemical in low intensity harvesting of rubber (Hevea brasiliensis). Currently the total requirement for rubber industry is being imported in ready-mixed form adding a considerable cost to the plantations. Therefore, a new ethephon formulation was developed locally and the present study aimed to assess its effectiveness under Sri Lankan condition. The newly developed ethephon formulation was tested against a commercially available formulation with a small-scale field trial. No significant variation was observed in sucrose availability in laticifers with the new ethephon formulation. Significantly higher thiol and lower inorganic phosphorous contents of latex in trees may ensure long-term sustainability of the new ethephon formulation as a yield stimulant in rubber. Average dry rubber content of latex and latex volume obtained from a tree was comparable with both formulations. Accordingly, dry rubber yield resulted from trees applied with new ethephon formulation was comparable with the existing formulation and average values were 83.22 g and 86.67 g, respectively for new and existing formulations.

PENGGUNAAN WAKTU DAN SUHU YANG IDEAL PADA PROSES PENGERINGAN KADAR KARET KERING LATEKS

Measurement of dryrubbercontent of latex (DRC) is very important factor in the trade transactions of rubber. Determination of temperature and drying time of latex’s DRC need to be studied in order to avo id the excessive difference between farmers and factories so that it can cause loss effect on sale andpurchase of latex transaction. This study aimed to determine the temperature and time factor of the DRC during the drying process and its interaction. The study used a complete random ized design (RAL) with twofactors, i.e. temperature (80oC, 90oC, 100oC, 110oC, 120oC) and time (2, 4, 6 hours) with 3 replications and as control was 100oC for 2 hours. The results showed that the interaction between temperature and time was apparent (p <0,010). The using of temperature variations of 90oC (4 and 6 hours), 110oC (2, 4, and 6 hours) and 120oC (2, 4, and 6 hours) is possible to replace standard temperature and time (100oC for 2 hours ), because it have no significant differences in the value of latex’s DRC.To prevent the latex sample browning and stickiness due to oxidation of high temperature, it can use temperature of 90oC-100oC and drying timeof 4-6 hours.

PEMANFAATAN ASAP CAIR DARI PELEPAH KELAPA SAWIT UNTUK MENINGKATKAN KUALITAS BAHAN OLAH KARET PETANI KARET

An effort in improving field latex quality has been conducted through community service activity for rubber farmers at Dusun Alur Hitam, Sekoci Village, Langkat Regency. The farmers generally use unrecommended coagulant such as fertilizer, extract of mengkudu or fern sap for coagulating their latex that can reduce the quality of rubber. The low quality of field latex, thus in turn reduce its selling price and income of farmers. Liquid smoke produced by pyrolysis of palm frond waste was proposed to be used as latex coagulant. Team of community service has designed and manufactured a pyrolysis reactor for this activity. The pyrolysis process produced brown liquid smoke with pH of 3 and a strong smoke smell. The produced liquid smoke can coagulate latex perfectly with the time needed were 2¢,25ʺ; 3¢,21ʺ and 4¢,29ʺ at the ratio of liquid smoke to latex were 1:10, 1:15 and 1:20 respectively with the use of liquid smoke of 2 mL. The dry rubber content of latex reached 73.48%. Thus, the utilization of smoke liquid can improve the dry rubber content as high 20.48% since the rubber buyer agents only set the dry rubber content of 53%. The elongation at break (EB) of latex was in the range of 165.55% - 286.93%. it is necessary to increase the knowledge and skill of rubber farmers. In the future, the establishment of farmer group or cooperative at Dusun Alur Hitam should be encouraged so as to facilitate the farmers in selling their product

Geo-informatics Techniques for Assessing Physiological Status and Productivity of RRIC 121 Genotype of Hevea brasiliensis (Rubber) under Different Harvesting Systems

Abstract Rubber (Hevea brasiliensis) one of the main plantation crops in Sri Lanka is the only plant species cultivated commercially for natural rubber harvesting. Novel systems for harvesting have been introduced but spatial distribution of photosynthetic potential determining key factor for sustainable cultivation has not been properly explored. Use of such techniques such as Satellite Remote Sensing (RS) and Geographic Information System (GIS) to analyse spatial and biological factors related to the productivity of rubber plantation with different harvesting systems is the main objective of the present study. Quikebird high resolution satellite images were used for RS analysis. Chlorophyll content of rubber leaves was measured using a SPAD-502 chlorophyll meter. Chlorophyll content and satellite images were analysed using GIS and spatial statistical methods to determine the variation in different harvesting systems. Yield data were collected from the study site and yield parameters were correlated with chlorophyll content and Normalized Difference Vegetation Index (NDVI) values. Results revealed all systems exhibited promising yield performance without significant deviation but slightly higher yield per hectare per year (YPH) and dry rubber content of latex (DRC) were recorded in quarter spiral based once in three days (S/3 d4) and weekly (S/2 d1 2d7) harvesting systems. Chlorophyll content and rubber yield showed direct correlation in all systems. NDVI vs chlorophyll showed positive correlation r2=0.65 and spatial distribution of chlorophyll and NDVI values demonstrated sound physiological status of plants across the plantation with different harvesting systems. Cost effective LIH systems showed better production trend demonstrating relatively higher yield while reducing tapping cost and labour. Satellite based remote sensing technique is an easy and efficient tool to estimate productivity of rubber plantation over a large area. Keywords: Chlorophyll, NDVI, harvesting, Remote Sensing, Rubber.

Temperature corrected ready-reckoner chart for determination of dry rubber content in Hevea latex using the metrolac

Rubber latex is collected by periodic excision of a thin shaving of the bark of Hevea tree. In addition to the volume, its value is determined by the dry rubber content (DRC) of latex. Dry rubber content of latex varies usually in the range of 20-45% and depends on several factors such as clone, season, climate and weather condition, stimulation program, tapping system, soil condition etc. Hydrometry (using the Metrolac) is the most widely used method in the determination of DRC in the Sri Lankan rubber industry. Metrolac measurements are highly vulnerable to temperature of the latex/water mixture. Existing ready-reckoner for Metrolac readings is valid only at 290C, hence the present study was aimed at developing a Metrolac ready-reckoner chart corrected for temperature variation in latex. Under natural and adjusted conditions, the new ready-reckoner chart showed an accuracy level of 84% on average in the estimation of dry rubber content whilst the average accuracy by the existing chart was below 50%. The Metrolac estimated DRC differed in the range of -12.69% to 9.25% from the actual under existing ready reckoner whilst that was limited to -7.56% to 5.31% with the use of new ready-reckoner chart.

Statistical Discrimination of Latex between Healthy and White Root Infected Rubber Tree based on Dry Rubber Content

Dry rubber content (DRC) is one of main material existing inside latex. It is usually in ranged of 25% - 45% of rubber latex. Statistical analysis are done to determine the discrimination of dry rubber content of latex between healthy and white root infected rubber tree. Based on 150 rubber trees and 10 clones tested, parametric test which include normality test, error-bar plot, and paired samples test are done. The result outcomes have shown that both data of dry rubber content of latex for healthy and white root infected rubber tree are normally distributed. Error-bar plot test is clearly indicated that there is visible discrimination between both cases. Paired samples test are done to reinforce this findings in terms of numerical p- value which is found to be less than 0.05. Thus, this indicate overwhelming evidence that healthy group can be discriminated from white root. Conclusively, changes in DRC content in latex can be correlated with white root disease infections of rubber tree.

Time Course Variation of Some Latex Physiological Parameters Associated with Yield of Rubber (Hevea brasiliensis) Grown in Eastern Province of Sri Lanka

Rubber cultivation in Eastern Province, is predominantly in the intermediate zone of which climatic conditions are considered to be sub-optimal for growing rubber. Due to low level of atmospheric RH%, latex flow tends to cease early after tapping in these areas. Turgidity of latex vessels associated with the water content of latex vessels decreases with the sunrise when evapotranspiration increases. Hence, time of commencing tapping greatly influences on the latex yield. Therefore, the present study was aimed to identify the best time of the day for latex harvesting through an assessment on latex physiological parameters. In order to identify the best time for tapping, variations in several physiological parameters together with latex yield were assessed at different time intervals, i.e., 04:00, 05:00, 06:00, 07:00 and 08:00 in two smallholder sites in the eastern Province. Latex volume, dry rubber content (DRC%), initial flow rate (IFR) and plugging index (PI) were analysed along with the environmental factors at the time of tapping. Latex volume per day (LVPD) was highly associated with the overall latex yield hence had become the prime factor concerned. The highest LVPD was recorded between 05:00 to 06:00 hrs. Dry rubber content of latex had increased after 06:00 h and that could be attributed to the water status of the trees which was governed by evapotranspiration. During 05:00-06:00 hrs time period, RH% was almost 100% and temperature was around 23° C. When tapping commenced after 06:00 h, the overall yield declined. There was a tendency of increasing the plugging index (PI) with the delay of tapping. Therefore, the study concluded that high yields could be obtained in this agro-ecological region if tapping is performed before 06:00 h. Keywords: Hevea , Intermediate zone, Rubber, Sub-optimal climatic conditions, Tapping time

Greater diurnal temperature difference, an overlooked but important climatic driver of rubber yield

The increase of rubber demand has led to rapid expansion of rubber plantations from optimal environments in the humid tropics of Southeast Asia into suboptimal environments in montane mainland Southeast Asia. Nevertheless, rubber yields can be surprisingly high in sub-optimal environments. This paper investigates climatic factors which contribute to the higher than expected rubber yields in a suboptimal environment in Jinghong, Yunnan, Southwest China. Two mathematical analysis methods were used to relate climate to rubber yield and dry matter content: partial least square regression and classification and regression tree models were used. Greater diurnal temperature difference was found to increase dry rubber yield, and has been previously overlooked as an explanatory factor. Average temperatures below 25.7°C, and more sunshine hours in the day before tapping, were also found to significantly improve dry rubber yield, although more sunshine hours during the month prior to tapping were found to reduce rubber yield. Lower relative humidity was found to increase dry rubber content of latex and increase yield. Greater diurnal temperature difference and more sunshine hours in a day before tapping facilitate photosynthesis and rubber formation. Lower relative humidity reduces the water content in the latex, thus increasing dry rubber content of the latex.In summary, this study finds that lower average temperature (within certain thresholds), greater diurnal temperature difference in both a day and a month before tapping, more sunshine hours in a day before tapping and lower sunshine hours in a month before tapping are the most important factors which promote dry rubber yield, and lower relative humidity in the day prior to tapping is the most important factor in determining dry rubber content of latex. Diurnal temperature difference has not been previously investigated as a driver of rubber yield. The case study site has a greater diurnal temperature difference than many other main rubber producing areas, which may contribute to explaining why rubber yields in Jinghong are higher than might be expected in a sub-optimal environment.

Preliminary Investigations of an Oil Based Ethephon Mixture (Motex Plus) on Low Intensity Harvesting Systems of Rubber

Low intensity harvesting (LIH) systems facilitate to reduce the cost of production (COP)through the reduction in the cost of tapping and also to minimise the harvester requirement inrubber plantations. In addition, considerable financial benefits are expected due to theincrease in economic lifespan of trees caused by the reduction in bark consumption. Tocompensate the yield loss due to lowering the intensity, 2-Chloroethylphosponic acid(ethephon) is used as a yield stimulant in LIH to enhance the yield per tapping. Allcommercial formulations of ethephon available in Sri Lanka have been water based.Although such formulations have an advantage in preparing different dilutions by mixingwith water, their long term effectiveness in field application are often questionable. A new oilbased formulation (Motex plus) has been introduced to Sri Lanka and therefore, the studyrecorded here was focused to assess its effectiveness in application of LIH.Performance of three low intensity systems recommended in Sri Lanka i.e. S/2 d3 (half spiralbased once in three days harvesting), S/2 d4 (half spiral based once in four days harvesting),and S/4 d3 (quarter spiral based once in three days harvesting) was tested with application of2.5% Motex Plus, every two months interval except during wintering, monthly and every twoweeks intervals, respectively together with S/2 d2 (half spiral based once in two daysharvesting) system for comparison. Dry rubber content of latex in LIH systems were above35% whilst it was about 33% in S/2 d2 system. Yield per tree per year in S/2 d3, S/2 d4 andS/4 d3 systems were 5.69 kg, 5.48 kg and 6.19 kg, respectively showing a slight higher yieldover the S/2 d2 system. Therefore potential reduction in the dose of oil based formulation isalso discussed. Number of trees affected with tapping panel dryness was comparably lower inLIH systems. Although the bark consumption per tapping was slightly higher in LIH systems,overall bark consumption has dramatically been reduced due to lesser number of tappingdays.

Specific Gravity of Latex and of Rubber

Abstract From observations on specific gravity and dry rubber content of latex, of centrifugal concentrates, and of latex-water mixtures, a number of attempts have been made to deduce the specific gravity of the rubber phase. Such estimates, after allowing for criticisms and adjustments which have been put forward, range from 0.901 to 0.914. But writers have made no attempt to consider how their calculations would be affected by treatments of the latex such as ammoniating and centrifuging, by different ways of evaluating the results, and by variations in temperature. When consideration is given to such matters almost all observations published during the last 20 years are found to be in good agreement one with another. Specific gravity, the ratio of the mass of a certain volume of a substance, at temperature t2, to that of the same volume of water, at temperature t1 is commonly designated dt2t2. To avoid excess affixes, when the temperature of the substance does not require to be stated, let:

A New Rubber Particle Count in Hevea Latex

Abstract SO MUCH confusion has grown up in the literature concerning the number of rubber particles in Hevea latex that at the present time there exists a thousandfold error in the currently published reports (1, 3, 8) of the one original determination of this number. Harries (4), Hauser (5), and Noble (8), each reporting the original work of Henri (6), give a count of 50,000,000 particles per cubic centimeter of latex, Harries not specifying the concentration, while Hauser and Noble indicate it to have been 8.7 per cent solids. On the other hand, Dubosc and Luttringer (2), also reporting the work of Henri, record a count of 50,000,000 particles per cubic millimeter in latex of unspecified concentration. The original paper of Henri (6) reported that he had found an average of 50,000,000 particles per cubic millimeter of latex having a specific gravity of 0.973 and containing 8.7 grams of solids per 100 cc. Preliminary counts undertaken by the author with a view to developing a rapid microscopic method for the determination of the dry rubber content of latex indicated that the results of Henri were considerably low. Since the number of microscopically visible particles is a fundamental property of latex, it was felt that a redetermination of this number would be of value.

Microturbidimeter for Determination of Rubber Content of Latex

Abstract It is desirable to devise a method for determining the dry rubber content of latex which will be both more rapid than the two trial coagulation methods and more precise than the hydrometric method. The turbidity of latex, depending upon the volumetric number and size of the suspended rubber particles, offers a satisfactory criterion for the determination of the rubber content of latex. A microturbidimeter, herein described, has been adapted to such determinations. It permits more rapid determinations of the rubber content than the two trial coagulation methods. Its precision is less than the lengthy trial coagulation method, involving coagulation, creping, and drying, but is probably greater than that of the shortened trial coagulation method involving only coagulation and creping. Its precision is approximately 1 per cent rubber in 35 per cent latex. The turbidity of latex obeys the turbidity-dilution law for rubber-content values less than 15 per cent. The use of color filters, transmitting the shorter wave lengths of light, minimizes the effects of a difference in the effective mean particle size of different kinds of latex.