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

Abstract

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.