It is well known that the productivity and the susceptibility to the tapping panel dryness (TPD) of Hevea brasiliensis are determined by the intrinsic feature of each clone but also by the tapping system. Thus, in order to establish the tapping system that minimizes the TDP occurrence an experiment was carried out in Côte d'Ivoire with four high yielding clones including, PB 235, PB 255, IRCA 18 and IRCA 111. Five tapping systems (d2 6d/7 0/y, d3 6d/7 4/y, d4 6d/7 6/y, d5 6d/7 8/y, d6 6d/7 10/y) were applied to these clones, corresponding to a range of 100 % to 30 % of tapping intensities. The results show that the occurrence of TPD is closely related to the tapping intensity and the tapping system which consists in tapping twice per week with one day rest (S/2 d3 6d/7 4/y), was found to be the best tapping system. A quadratic relation was found between the rate of the TPD and the tapping intensity. Thus the clones IRCA 18 and IRCA 111, like PB 235 and PB 255, belong to the active metabolism clones. These clones also showed their adherence to the group of high rubber producer clones. This experiment also gave further evidence that the production of a tree for the tapping strongly depends on the intensity of tapping. It has also indicated that the intensity of tapping governed the tapping panel dryness rate among the clones having active metabolism, such as IRCA 18, IRCA 111, PB 235 and PB 255.
The cultivation of Hevea brasiliensis, main source of natural rubber, is facing a problem of scarcity and/or high cost of skilled labour. One of the means to remedy this constraint is to reduce the intensity of tapping. This work aims at studying in clone PR 107 of Hevea brasiliensis, in south-eastern Côte d'Ivoire, according to the nature of bark and the orientation of tapping, low intensity tapping systems but highly stimulated (S/4U d3 6d/7 . ET5.0% Pa1(1) 8-10/y(m) and S/2 d6 6d/7 . ET2.5% Pa1(1) 8-10/y(m)) enabling to reduce the need for tappers by 10 and 50% compared to a traditional tapping system (S/2 d3 6d/7 . ET5.0% Ba2(2) 4/y(3m) control). This study was carried out on the basis of agronomic and physiological criteria. The results of 21 years of exploitation have shown that reductions in the intensity of tapping were compensated for partially or totally, in terms of yield, by the strong stimulations without causing damage to the vegetative, physiological and health status of trees. The best low intensity tapping systems can be alternatives to the traditional exploitation system in order to reduce the need for tappers and thus make up for a deficit and/or a high cost of labour. These tapping systems are, on downward tapping on BI, S/2 d6 6d/7 . ET2.5% Pa1(1) 10/y(m); on upward tapping on HO, S/4 U d3 6d/7 . ET5.0% Pa1(1) 10/y(m) and on downward tapping on HO, S/4U d3 6d/7 . ET2.5% Pa1(1) 10/y(m).
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