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

Abstract

The classic latex harvesting system consists of top-downward tapping for nine years before being immediately followed by upward 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 downward tapping to ensure good performance of agrophysiological parameters in upward 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 downward tapping (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 upward tapping of these metabolically active clones preceded by 5 and/or 6 years of downward 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 upward 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 tapping for 5 and/or 6 years allows these clones to express their best potential in upward tapping. These results are satisfactory and respond exactly to the concerns of the farmers.