Influence of Tapping Depth on Rubber Yield and Tapping Quality in Rubber Tree Plantations in Southeastern Côte d'Ivoire

Aims: Rubber tree (Hevea brasiliensis Muell Arg.) is the main source of natural rubber. Its cultivation generates significant income for several companies and farmers around the world. However, its exploitation is threatened by the considerable drop in rubber yield which is due to the ignorance of tapping criteria in particular the optimal tapping depth. This study aims at improving rubber yield. 
Place and Duration of Study: The study was carried out in agro-industrial plantations of rubber tree in southeastern Côte d'Ivoire from June 2020 to January 2021. 
Methodology: The study took place in two phases: the first consisted in assessing the tapping depth of the plantations and the second in studying the influence of the different tapping depths on rubber yield and tapping quality. The first study was carried out with 347 tappers in 954 tapping tasks. The second study focused on 4 rubber tree clones (PB217, IRCA 41, IRCA 230 and IRCA18) belonging to the three metabolic activity classes. These clones were subjected to 4 treatments (T0: tapping to a depth of 0 to 1.5 mm; T1: tapping to a depth of 1 to 2 mm; T2: tapping to a depth of 1 to 1.5 mm, T3: tapping to a depth of 1.5 to 2 mm) in a completely randomized block design with 4 repetitions. This comparative study was carried out on the basis of yield and tapping quality parameters (bark consumption, wounds). 
Results: The results of the first study showed that the average tapping depth of the plantations inspected is 1.44 mm in half-spiral downward tapping and 1.82 mm in a quarter-spiral upward tapping. The tapping depth is influenced by the height of the tapping panel and by the clone. The results of the second study showed that tapping depth influences rubber yield and tapping quality. Indeed, tapping to a depth between 1 and 1.5 mm from the cambium induces the most significant yields but causes poor tapping quality. In contrast, tapping to a depth between 1 and 2 mm from the cambium gives lower yields but makes it possible to show better tapping quality. 
Conclusion: The tapping depth is influenced by the height of the tapping panel and by the clone. The tapping depth influences rubber yield and tapping quality.