Latex Harvesting Research Articles

Overexpression of the EuFPS5 gene in Hevea brasiliensis fails to produce Eucommia rubber but affects the biosynthesis of natural rubber

The Eucommia ulmoides rubber (EuR) is a naturally occurring long-chain trans-1,4-polyisoprene with extensive applications but high production costs. Previous studies suggest that the Eucommia farnesyl diphosphate synthase 5 (EuFPS5) alone is capable of catalyzing the biosynthesis of EuR. As the most high-yielding cis-polyisoprene-producing plant species with a cost-effective latex harvesting system, Hevea brasiliensis exhibits the potential to produce EuR at a lower cost. Via Agrobacterium-mediated transformation, this study generated a transgenic Hevea line overexpressing EuFPS5 (EuFPS5oe). The EuFPS5oe Hevea plants exhibited slightly wrinkled leaves, but no significant difference in growth vigor compared to the wild type control (WT). 1H and 13C nuclear magnetic resonance (NMR) analyses indicated that the rubber of 1-year-old EuFPS5oe plants was identical to that of WT, suggesting that EuFPS5 alone is not sufficient to catalyze the biosynthesis of EuR in Hevea. However, compared to the WT, EuFPS5oe plants showed significantly increased rubber content in the leaves, while the rubber molecular weight in the latex decreased. LC-MS/MS analysis showed that the EuFPS5oe latex contained a comparable level of IPP, but a significantly higher level of FPP than the WT. Taken together, our study suggests a role for EuFPS5 in the biosynthesis of FPP in Hevea, provides in vivo evidence that under limited IPP supply, higher FPP level increases rubber production but decreases rubber molecular weight, and thus lays a foundation for future genetic improvement of natural rubber production in Hevea brasiliensis.

Long Term Effect of Low Frequency Tapping Systems Applied to Rubber Tree (Hevea brasiliensis), Clone RRIT 251, on Agronomic Performance in Upper Southern Thailand

Clone RRIT 251, a primary clone, was developed by RAOT (Thailand) with promising high yield potential. Low frequencies of tapping (LFT) was tested using 8-year-old trees to characterize the performance of the clone RRIT 251 under such latex harvesting systems. The aim of the study was to assess the response of the yield to LFT related to some biochemical indicators of the latex cells’ metabolism. The experiment was established at the Sithiporn Kridakorn Research Station of Kasetsart University, Prachuap Khirikhan Province, Thailand. The experimental randomized Fisher block design consisted of the 3 treatments. These were abbreviated to T1: S/2 d2 opening BO-1 at 1.5 m, T2: S/2 d3 ET 2.5 % Pa1 (1) 6/y opening BO-1 at 1.3 m and T3: S/2 d4 ET 2.5 % Pa1 (1) 8/y opening BO-1 at 1.2 m. Three replications were conducted with 55 trees per treatment in each experimental plot. Analysis of variance (ANOVA; F test) has been used to compare treatments using Duncan’s multiple range test (DMRT) at a significant level of p < 0.05. Results showed that daily yield greatly increased when using lower tapping frequencies. More than 10 years of tapping, panel management and location of the tapping cut on the panel in downward tapping have significantly impacted yield. Tapping on virgin bark at d3 and d4 frequencies gave higher yield than d2 frequency on renewed bark. Good panel management, combined with tailored stimulation and reduced tapping frequency showed greater efficiency. Results were encouraging. It might be considered that these low tapping frequencies systems can be tested by smallholders and then transferred at the farm gate in Thailand. GRAPHICAL ABSTRACT

A review of low-frequency latex harvesting systems that lessen the tapper shortage problem of the smallholders' natural rubber production

Smallholders' rubber production is encountering problems of skilled tapper shortage and high production costs resulting from increased worker wages and the substantial growth of new mature areas. Low-frequency latex harvesting system (LFLHS) effectively improves tapper productivity with long-term optimum yield by reducing the tapper requirement. LFLHS reduces tapper requirement by 33% to 67% of the conventional harvesting systems. Under the d3 (tapping every three days) frequency harvesting system, a tapper is assigned to cover three tasks, and his productivity is at least 30% higher than that of the d2 (alternative daily) frequency harvesting system. The cumulative yield of LFLHS is comparable to that of d2 frequency. It is economically profitable when the cumulative yield of LFLHS reaches 90% of the d2 frequency tapping as a break-even yield. Its low number of tapper requirement and high productivity saves tapping cost. 20% to 55% of tapping cost can be reduced by shifting the harvesting frequency from d2 to d3. The virgin bark of basal panels could be tapped at least four to ten years more than conventional tapping systems. The low bark consumption allows sufficient time for the regeneration of bark tissues resulting in a potentially higher yield from the renewed bark. Thus, sustainable economic yield is achievable for a productive lifespan of 30 to 35 years from the LFLHS. These advantages of LFLHS contribute to reducing the tapper requirement and cost of production, ensuring increased profits and a longer economic lifespan of rubber production.Keywords: Latex harvesting system, Tapper requirement, Tapper productivity, Tapping cost

Evaluation of Cutting Stability of a Natural-Rubber-Tapping Robot

Natural rubber is a crucial raw material in modern society. However, the process of latex acquisition has long depended on manual cutting operations. The mechanization and automation of rubber-tapping activities is a promising field. Rubber-tapping operations rely on the horizontal cutting of the leading edge and vertical stripping of the secondary edge. Nevertheless, variations in the impact acceleration of the blade can lead to changes in the continuity of the chip, affecting the stability of the cut. In this study, an inertial measurement unit (IMU) and a robotic arm were combined to achieve the real-time sensing of the blade’s posture and position. The accelerations of the blade were measured at 21 interpolated points in the optimized cutting trajectory based on the principle of temporal synchronization. A multiple regression model was used to establish a link between impact acceleration and chip characteristics to evaluate cutting stability. The R-squared value for the regression equation was 0.976, while the correlation analysis for the R-squared and root mean square error (RMSE) values yielded 0.977 and 0.0766 mm, respectively. The correlation coefficient for the Z-axis was the highest among the three axes, at 0.22937. Strict control of blade chatter in the radial direction is necessary to improve the stability of the cut. This study provides theoretical support and operational reference for subsequent work on end-effector improvement and motion control. The optimized robotic system for rubber tapping can contribute to accelerating the mechanization of latex harvesting.

VALIDATION OF MORPHOLOGICAL CRITERIA FOR CLONAL IDENTIFICATION IN BUDWOOD GARDENS OF RUBBER TREE (HEVEA BRASILIENSIS MUELL. ARG.) CLONES USING MICROSATELLITE MARKERS

The inability of almost all rubber tree nursery growers to distinguish between the different rubber tree clones in a budwood garden (JBG) often leads to clonal mixtures. This makes the application of latex harvesting technology unsuitable, which negatively impacts the yield and / or the economic life of the plantations. To overcome this problem, a clonal identification method based on the use of seven (7) morphological criteria in JBG (budwood garden) was developed. Knowing that the morphological criteria are influenced by the environment, the visual recognition of the plants seems approximate or inefficient. In order to check the effectiveness of the morphological criteria, five (5) rubber tree genotypes from two JBGs (budwood gardens) were characterized both morphologically and by microsatellite markers. Characterization by microsatellites was carried out on twelve (12) loci and involved a sample of 25 individuals per genotype. This first study on the use of microsatellite markers revealed that three (3) microsatellite markers (Hb36, Hb43 and Hb110) best discriminate the genotypes (GT1, PB217, IRCA41, IRCA230 and IRCA331) cultivated in Côte d'Ivoire. It also showed that an individual declared non-compliant by the morphological method has 89% chance of being genetically non-compliant, one could be mistaken by 11% in declaring an individual non-compliant while it is genetically compliant (type I error). In addition, an individual declared compliant by the morphological method has a 76% chance of being genetically non-compliant, one could also be mistaken by 24% in declaring compliant while it is genetically non-compliant (type II error).

ASSESSMENT OF TAPPING QUALITY IN RUBBER TREE CULTIVATION IN COTE DIVOIRE: CASE OF YAMOUSSOUKRO, TIASSALE AND ANGUEDEDOU PLANTATIONS

Rubber tree cultivation is booming in Cote dIvoire, making the country rank 1stin Africa. However, plantations are destroyed prematurely due to poor tapping qualities. In order to improve tapping quality and by extension rubber yield, a study was conducted in Cote dIvoire in the towns of Yamoussoukro, Tiassale and Anguededou. This study was conducted on the basis of a survey on the characteristics of the plantations and the tappers of 23 plantations, followed by a tapping quality check. The results showed that tapping commencement of plantations was later in Yamoussoukro (9.2 years) than in Tiassale (6.7 years) and Anguededou (6.8 years). Furthermore, the Yamoussoukro plantations were younger and smaller (1 to 4 years of latex harvesting and 2 ha on average) compared to those of Tiassale and Anguededou (1 to 12 years of latex harvesting and 10 ha on average). The sociological characteristics of tappers showed that they are only men, most of whom have been trained in tapping techniques (91% of tappers). It appears from this study that tapping quality was poor in Anguededou and good in Tiassale and Yamoussoukro. Finally, the correlation analyses showed that tapping quality was not related to tappers but rather to theirtapping knives. The tappers must therefore use a good tapping knife for tapping and perform the tapping in accordance with established tapping standards.

Research trend in latex harvesting of rubber tree (Hevea brasiliensis Muell. Arg.) based on bibliographic analysis

The rubber plant (Hevea brasiliensis Muell. Arg.) is the main natural rubber-producing species. Researches on rubber has been carried out for more than a century. Researchers and academics should stay up to date with the current scientific issues including latex harvesting in H. brasiliensis Muell. Arg. This article presents a bibliometric analysis of scientific literature indexed by Scopus and published from 2018 to 2022. The literature was categorized into three sub-topics i.e., latex harvesting techniques (38 papers), physiological mechanisms (41 papers), and oxidative stress induced by latex harvesting practices (18 papers). Metadata validation was performed using Mendeley reference management software and bibliometric analysis was carried out using VOSviewer bibliometric network visualization software. The results on the latex harvesting technique showed that most of the articles were related to the development of automatic tapping machines. This indicates a trend that latex harvesting techniques are likely shifting from manual tapping to fully automated methods using machines and robots. In terms of physiological mechanisms related to latex production, the mechanism of rubber biosynthesis and ethylene response at the genomic, transcriptomic, and proteomic levels predominated the finding. Research on oxidative stress induced by tapping mainly focuses on the effects of mechanical wounding and ethylene stimulation, while research on antioxidants is still limited. In the past five years, biotechnology and molecular analysis are the main tools to study physiological mechanisms and oxidative stress. This can be a consideration for scientists and research institutions to develop laboratories and human resources to be able to conduct molecular-based research.

Agronomic and Financial Assessment of a Tapping System Reducing the Shortage of Tapping Labour in Rubber Tree Cultivation in Southeastern Côte d’Ivoire

Rubber trees are the main source of natural rubber and a source of income for several companies and farmers around the world. However, its latex harvesting is threatened by the lack of tapping labour which can cause a considerable drop in rubber yield or even the collapse of this sector. This work aims to evaluate agronomically and financially a tapping system reducing the shortage of tapping labour. The study was carried out at the Société Africaine de Plantations d'Hévéa (SAPH) of Toupah in southeastern Côte d'Ivoire, during three months (from April to June 2018). Rubber tree clones comprising the three main metabolic activity classes, namely GT 1, RRIC 100, IRCA 230 and PB 217, with different years of latex harvesting were selected and subjected to two treatments (normal tapping and tapping system reducing the shortage of tapping labour) in a completely randomized blocks design with 4 repetitions. This comparative study was carried out on the basis of the agronomical parameters and the profitability of the tapping tested. The results showed that compared to normal tapping, tapping system reducing the shortage of tapping labour is more productive (+17%) and profitable (+18%). This tapping system reduces the operating expenses and social expenses by 3% and the shortage of tapping labour by 25%. It is an alternative to reduce the enormous shortage of tapping labour observed in Côte d'Ivoire and around the world.

Determination of the Execution Time of Down Tapping Allowing a Good Performance of Agrophysiological Parameters in Reverse Tapping of Fast Metabolizing Rubber Clones PB 260 and IRCA 18

The classic latex harvesting system consists of top-down tapping for nine years before being immediately followed by reverse tapping. This period is often considered too long by the farmers. To address this concern, a study was conducted to determine the best period for down tapping to ensure good performance of agrophysiological parameters in reverse tapping of fast metabolising rubber clones. For this purpose, the PB 260 and IRCA 18 clones were used as plant material in Divo and Daoukro respectively, where the experiments were conducted. Five time frames for down-bleeding (5, 6, 7, 8 and 9 years = control) and two concentrations of ethephon (ET) stimulating paste (2.5 and 5% ET), except for the control which is stimulated only at 5% ET, were tested. The experimental design was a Fisher block design with 9 treatments and 4 replicates. Rubber productivity results (5262 ± 205 and 4951 ± 351 kg.ha-1.yr-1) showed that reverse tapping of these metabolically active clones preceded by 5 and/or 6 years of down tapping was the best (3723 ± 29 kg.ha-1.yr-1 ; control). Rubber production and average annual increment from these tapping periods (4.00 ± 0.42 and 3.60 ± 0.00 cm.yr-1 ; control) were the highest. Productivity gains were 41% for reverse tapping at 6 years stimulated at 5%. The dry notch rate was relatively low (3.30% LEM and 0% dry trees). The physiological profile was generally good. These results indicate that downward bleeding for 5 and/or 6 years allows these clones to express their best potential in reverse bleeding. These results are satisfactory and respond exactly to the concerns of the farmers.

Evolution of the Rate of Live and Tapped Trees of Hevea brasiliensis Clones, Muell. Arg. the First 15 Years of Plantation Establishment

The density of tapped rubber trees in a plantation is a determining parameter of its productivity. It is related to the number of trees planted per hectare, the evolution of which can be influenced by several factors that act on the trees from the year of establishment to the time of tapping. To this end, a study to determine the evolution of the rate of live trees and tapped trees of eight rubber clones during the first fifteen years of establishment was carried out in southwestern Côte d'Ivoire. At opening, rubber trees planted at 510 trees/ha (7 m x 2.80 m) were bled in a descending half-spiral at different tapping and stimulation frequencies. The experimental design was a Fisher block design with 6 treatments (d2, d3/4y, d4/4y, d4/8y, d5/8y, d6/10y) and 3 replications. The results revealed that the rate of live trees and tapped trees was not influenced by either clone or latex harvesting treatment. The rate of live trees decreased progressively from the immature phase of the plantation (94.71 ± 1.34%) to the end of the downward tapping (91.55 ± 0.67%). The rate of tapped trees increases from the time of planting (69.51 ± 8.03%), over the years (92.00 ± 1.39%) until it equals the rate of live trees (92.00 ± 1.08%) before gradually decreasing to 88 ± 3.78%. It should be noted that the factors influencing the evolution of the rates of live and taped trees caused less damage to the rubber trees. And this influence is not dependent on clone, metabolic activity class and latex harvesting system.

Latex Harvesting Technologies Adapted to Hevea brasiliensis Muell Clones GT 1; RRIC 100 and BPM 24 Arg. (Euphorbiaceae) belonging to the Moderate Metabolism Class in the Socio-economic Context of Côte d'Ivoire

Improving the productivity of rubber trees has always been a major concern for rubber farmers. The majority of growers opt for overexploitation of the trees. This disturbs the physiological balance of the rubber trees, which leads to the recrudescence of tapping panel dryness and rather to a drop in production. To solve this problem, the present study proposes to define a latex harvesting technology (or technologies) for the moderate metabolism clone class that will allow the improvement of plantation yield and the increase of the economic life of the trees. To achieve this, the GT 1, RRIC 100 and BPM 24 clones of the moderate metabolism class were used as plant material. The results showed that the reduction in tapping frequency had no negative effect on the vegetative state of the trees. This reduction was compensated by a high number of annual stimulations, which resulted in high dry rubber production. Analysis of dry rubber production, radial rubber growth and tapping panel dryness rate indicates that the moderate metabolic class clones performed better with the latex harvesting technologies S/2 d3 6d/7 ET2.5% Pa1(1) 6/y; S/2 d4 6d/7 ET2.5% Pa1(1) 6/y and S/2 d5 6d/7 ET2.5% Pa1(1) 1.

Effect of Late Upward Tapping on the Productivity of the Metabolically Active Hevea brasiliensis Clone PB 260 in Southwestern Cote d'Ivoire

In order to evaluate the improvement of rubber productivity of rubber trees by late upward tapping. A study was conducted at SCASO (Société Civile Agricole du Sud-Ouest) on the PB 260 clone of the active metabolic class. The experimental set-up is a Fisher block design with eight treatments and three replications. The treatments compared were bled in reverse in the eleventh year of harvest, in quarter spiral every 3, 4, 5 and 6 days, with stimulation frequencies of 6, 8, 10, 12 and 13 times a year. The parameters measured were rubber production, isodiametric growth, sensitivity to dry notching of trees and physiological profile. The results show that the different latex harvesting technologies improve the rubber productivity of PB 260 (5469 kg.ha-1.yr-1) with a low dry-nut rate (1.2%) and satisfactory radial vegetative growth (3.9cm.yr-1). The physiological profile of the trees is balanced, but the treatments significantly influenced the different parameters except sucrose. Trees bled in S/4U d3 gave better results due to their high yield with an acceptable dry notch rate. Late reverse tapping is therefore a good latex harvesting technology for improving rubber productivity after down tapping.

Design, development and evaluation of latex harvesting robot based on flexible Toggle

Natural rubber latex is an important energy material. However, the harvest of latex is still manual, and there are few researches on automatic work. This paper proposed a method for robot to harvest from each rubber tree without stopping. The robot toggled the collection cup through the flexible actuator, the cup poured out the latex and rotated to the next collection position. In this way, it not only completed the harvest work, but also prepared for the next collection. Aiming at the problem of latex splashing during rapid toggle, the structural parameters of the collection cup and the flexible actuator were modeled and studied. This method made the rotation speed of the collection cup smoother and avoids splashing. To enable the robot to accurately complete the harvesting work, this paper used two-dimensional Light Detection and Ranging (LiDAR) and ranging sensor to locate the space position of the collection cup. The results show that when the toggle speed is 0.5 m/s and the latex volume is 300 ml, the average shaking height is 3.58 mm. In the field test, the lateral error of positioning is less than 8.86 mm, and the height error is less than 0.72 mm; the average harvest rate is 98.18%. The robot has high efficiency and good stability, and can be applied to the rubber plantation to harvest automatically.

Design, development, and field evaluation of a rubber tapping robot

AbstractModern robotics has made great strides in the field of agricultural harvesting. In the field of rubber tapping, however, there are still significant challenges to be faced. As one of the few agricultural harvesting areas primarily manual, rubber tapping requires precise control of the knife in the forest's unstructured environment at night. This paper presents the design of a rubber cutting robot for natural rubber plantations. An upgraded spatial spiral trajectory is established by analyzing the trunk and manual rubber cutting trajectories for the operation of a six‐axis tandem robot arm. A compact binocular stereo vision system achieved the initial perception of the parameters required for the cutting trajectory. Besides, an integrated end‐effector was developed to enable further precise perception of the cutting trajectory and cutting operations. The system was tested in the field at a rubber plantation in Hainan Province. The upgraded trajectory's adaptability and the accuracy and efficiency of the starting point positioning algorithm were verified. The operational performance of the complete system was evaluated to help guide future improvements. The error of the start point locating is 1.0 0.1 mm, and the execution time is 17.01 3.65 s. The bark consumption—cutting depth setting of (2.0 and 5.0 mm) is more appropriate for the rubber tapping robot. Then the accuracy of chip thickness and chip width is about 1.73 0.28 mm, and 5.07 0.13 mm, respectively. Furthermore, the accuracy of chip weight is 1.99 0.24 mm. The average operating time of the whole tapping operation is 80 5 s. Future work will include improvements in system stiffness and robustness. This study demonstrates the potential of applying industrial robotics to the field of latex harvesting. Robotics may be a future development towards mechanized rubber tapping.

Contribution to Natural Rubber Production without Exogenous Hormonal Stimulation

Rubber production and especially its increase absolutely depend on the activation of the latex-producing metabolism. Can the latex-producing metabolism activation mechanism developed by rubber tree lead to higher yield without exogenous hormonal stimulation? In order to verify this decisive hypothesis, several works, carried out for nine years in Southern Côte d’Ivoire, were conducted on some 15 clones (IRCA 18, IRCA 209, IRCA 111, IRCA 130, PB 235, PB 260, PB 280, PB 330, PB 310; GT 1, BPM 24, RRIC 100; PB 217 and PR 107) of the three metabolisms respectively, active, moderate and slow, with two main statistical designs. On a small scale, in a “one-tree plot” design, the same latex harvesting system, tapping in d4 with different hormonal stimulation regimes (0/y; 2/y; 4/y; 6/y; 8/y; 13/y; 18/y; 26/y, 39/y and 78/y), has been applied to all treatments. In a randomized complete block design, different tapping frequencies (d2, d3, d4, d5 and d6) and hormonal stimulation (0/y, 4/y, 8/y and 10/y) were applied. Whatever the stimulation regime, the average g.t-1.t-1 of the unstimulated control (56) of the active metabolism clones (PB 235, PB 310, IRCA 111 and IRCA 130) over 9 years was statistically the same order that of the stimulated patterns (54). The average g.t-1.t-1 of the control (60) was lower than that of the highest yielding stimulated patterns (67) of the clones (PB 330, PB 280, PB 260, IRCA 18 and IRCA 209). The average g.t-1.t-1of the unstimulated control (49) was significantly lower than that of the highest yielding stimulated treatment (57) of moderate metabolism clones (GT 1, BPM 24 and RRIC 100). The average g.t-1.t-1 of the unstimulated control (39) was significantly lower than that of the highest yielding stimulated treatment (70) of slow metabolism clones (PB 217 and PR 107). On a large scale and at tapping frequency (d2), the unstimulated latex harvesting system (d2 0/y) showed an average yield of (2341; 2266 and 1849 kg.ha-1.year-1 for the active, moderate and slow metabolisms, respectively) statistically comparable to those of the highest yielding tapping frequencies d3, d4, d5 and d6 all latex harvesting systems combined for the clones studied (2388; 2348 and 2256 kg.ha-1.year-1). These results show that it is possible to produce natural rubber without exogenous hormonal stimulation by judiciously playing on tapping intensity.

Relationship between the Intensity of Latex Harvesting and the Tapping Panel Dryness Expression of Clone GT 1 of Hevea brasiliensis Muell Arg in South-East Côte d'Ivoire

Tapping panel dryness is an important limiting factor in rubber productivity of Hevea brasiliensis. In order to assess the sensitivity to this syndrome, the effect of two intensive latex harvesting technologies on moderately metabolized GT1 clone, has been studied in the South-Eastern region of Côte d'Ivoire. The rubber trees were planted according to the experimental mono-tree device, "One tree one plot design" a tree constituting a repetition, and 31 trees per treatment, selected on circumference and health status criteria. The parameters measured were rubber production, circumference increase, physiological profile and tapping panel dryness sensitivity. The results showed that induction of tapping panel dryness in latex harvesting system, S/2 d/3 6d/7 ET 10 % Pa 1 (1) 1/ w) was significantly low (0.18 ± 0,22 %) than that of the control (S d/1 6d/7 unstimulated, 1.43 ± 1.45 %). Productivity of this particular system was also good (62 ± 16.32 g.a-1.s-1) and it especially has less stress that can cause physiological fatigue, or even the notch dry. Otherwise, Rubber production, radial vegetative growth, physiological parameters of the latex and the tapping panel dryness rate were influenced by the two treatments applied to GT 1. In addition, the medium and high sucrose contents (16.5 ± 3.01%) and thiol group (0.51 ± 0.13 mmol.l-1) of the latex in the treatment (S/2 d/3 6d/7 ET 10% Pa 1 (1) 1 / w), were instrumental in the response to this stimulation. The sensitivity to the tapping panel dryness is in very close linear relation with the harvest intensity of the latex to which the GT 1 clone has been subjected. These results corroborate and confirm the moderate sensitivity to the tapping panel dryness of GT 1 clone.

Quantitative Assessment of the Agro-physiological Advantages of Upward Tapping in Relation to the Downward Tapping of the GT 1 and PB 260 Rubber Clones [Hevea brasiliensis, Muell. arg. (Euphorbiaceae)] in Southwest Côte d'Ivoire

The downward tapping on virgin bark of the lower panel (BO) is immediately followed by the upward tapping on virgin bark of the upper panel (HO), consecutively. To determine the agro-physiological advantages of one tapping over another, a study of the downward and upward tapping of the GT 1 and PB 260 clones of Hevea brasiliensis was carried out in southwestern Côte d'Ivoire. For this purpose, the rubber trees were tapped in a downward half-spiral (S/2) at the opening for nine consecutive years, followed by upward quarter-spiral tapping (S/4U) for four consecutive years. The agronomic parameters (rubber production and vegetative growth), tapping panel dryness and the latex micro-diagnosis, were evaluated. For GT 1 clone, the transition from the downward tapping panels to the upward tapping panels resulted rubber productivity gain of 35%. Meanwhile for PB 260, rubber productivity gain was 37%. Regardless of the clone and tapping direction, the higher the rubber productivity of a respective tapping panel, the lower the isodiametric growth of the tree trunk was recorded. Latex harvesting systems, and clone’s combination, did not influence the tapping panel dryness or the physiological profile of the trees. Finally, it should be concluded that upward tapping is more productive than downward tapping, but the quantification of the gains in this rubber production depends on the clone.

Energy Fluxes and Evapotranspiration in a Rubber Agroecosystem of the Southern Thailand

Evapotranspiration (ET) plays an important role in land surface atmosphere interaction which significantly drives hydrological cycle, vegetation functioning resulting to agricultural production. In this study, observations of energy fluxes, energy partitioning, and evapotranspiration (ET) were conducted on a monoclonal stand of rubber trees (Hevea brasiliensis) plot (clone RRIM 600) in 2017. The forestry population was 17 years old and had been tapped continuously over 10 years for latex harvesting at the Rubber Estate Organization station in Na Bon district, Nakhon Si Thammarat province in Thailand. The ET rate and associated energy fluxes were determined by means of eddy covariance (EC) method and complemented by micrometeorological measurements at 25 m tall tower. Tree stands were spaced on plots of 3.0×7.0 m2 with mean canopy height of 22 m. Data were collected during January 1 to September 27, 2017. Results found that the energy balance closure of the rubber agroecosystem was approximately 78 %. Overall, the latent heat (LE) flux was the main term of energy exchange (58 - 60 %) due to its dominance across the growing season. The ratios of the latent heat (LE) and sensible heat (H) to net radiation were 0.58 and 0.24 throughout the period of study, respectively. Moreover, the daily mean of evapotranspiration (ET) was 7.16 mm.d-1 over the whole period of this study. However, a slightly higher rate of daily mean ET (7.35 mm.d-1) was indicated during the foliage period than during the leaf senescence period due to sufficient soil moisture associated with high rate of seasonal precipitation. It is concluded, that ET is an extremely sensitive variable to understand in energy flow in this ecosystems as well as a precursor for presetting condition for droughts prognosis (forecast) in a rubber ecosystem.

Training induced knowledge and adoption of harvesting technologies in rubber smallholdings in the Kegalle district of Sri Lank

This study was carried out to evaluate the impact of training on improvement of knowledge and adoption of technologies developed by the Rubber Research Institute of Lanka (RRISL) for harvesting of rubber in the smallholder sector. The scores which were used to measure the knowledge (KNOW) and adoption (ADOP) of latex harvesters on recommendations related to latex harvesting were also used to evaluate whether systematic training could improve knowledge/adoption. Equal number of trained and non-trained harvesters; 80 each were selected for the study in Kegalle district. A questionnaire survey and field level observations were conducted in 2017, employing equal numbers from the two categories; Latex Harvesting Assistants (LHAs) who harvest their own rubber lands (OPER=1) and those who are hired by land owners (OPER=0) within the categories of trained and non-trained LHAs. The increase in KNOW and ADOP due to systematic training was statistically significant. The respective mean scores for trained and non-trained groups (for KNOW; 70 and 38, t=-12.85, P<0.001 and for ADOP; 71 and 40, t=-10.34, P<0.001) signifying that training has increased KNOW and ADOP by 84% and 78%, respectively. In the trained group, significant differences were observed for both KNOW and ADOP for OPER (for KNOW; OPER1=82.9 and OPER0=57.8; t=-6.45, P<0.001) (for ADOP; OPER1=84.3 and OPER0=56.3; t=-6.36, P<0.001), indicating that KNOW and ADOP to be high with OPER1. The experience in harvesting was negatively correlated with KNOW (r=-0.528, P<0.001) and ADOP (-0.638, P<0.001). Participation in other extension activities was positively related with KNOW (r=0.341, P<0.01) and ADOP (r=0.390, P<0.01). The variables, such as age, gender and education level and job satisfaction did not have significant relationships with KNOW and ADOP. It is evident that systematic training on rubber harvesting enhances knowledge and adoption of recommended practices, which may eventually improve the productivity of rubber smallholdings. Hence, this training is worth continuing for the improvement of future performance of the smallholder rubber sector.

Agronomic Performance of Hevea brasiliensis Muell. Arg. Clone IRCA 331 Grown in Southwestern Côte d'Ivoire

In order to test the agronomic performance of the newly developed clones, a Large-Scale Clone Trial (LSCT) comprising Hevea brasiliensis clones GT 1, IRCA 202, IRCA 331, IRCA 707, PB 280 and PB 310 was established in southwestern Côte d'Ivoire. They were planted in completely randomized blocks with six clone treatments and four replications of 112 trees per clone. The measured parameters included isodiametric growth of the trunk, rubber yield, trees stand, latex physiological parameters and sensitivity to tapping panel dryness (TPD). Collected data was analyzed using Statistica 7.0 statistical software. After ten years of downward tapping and four years of upward tapping, clone IRCA 331 showed significantly higher rubber productivity than all other clones. Its productivity gain, relative to the reference control GT 1, was 63% in downward tapping and 80% in upward tapping. Despite its high level of productivity, the annual rate of isodiametric growth of clone IRCA 331 tree trunks (2.56 cm/year) remained statistically equivalent to that of clone GT 1 (2.62 cm/year) at latex harvesting stage. In addition, the physiological profile of clone IRCA 331 was good and similar to that of the control. Clones IRCA 331, GT1 and PB 280 got the lowest sensitivity to TPD. However, only clones GT1 and IRCA 331 maintained a good stand of tappable trees throughout the experimental period. This experiment highlighted the agronomic performance of the clone IRCA331 and allowed to put it in class 1. Clone IRCA 331 can therefore be used as a clone of first choice to improve national productivity.