Reduced tapping frequency and DCA tapping systems : Research towards improvement of Thailand rubber plantations productivity

Continuous decrease of the size of Thai rubber smallholdings for the last twenty years (from 4 ha in 1980 to 1.7 ha nowadays) has led to general adoption of very intensive tapping systems by most of Thai rubber farmers. Beside 1/2S d/2 7d/7, systems like 1/2S d/1 2d/3, 1/3S d/1 2d/3, 1/3S d/1 3d/4, or even more intensive are quite usual on Thai rubber farms, resulting in possible over exploitation, high TPD (tapping panel dryness) rates, short life-cycle of plantations and rather low productivity. The current report presents the results of a three years experimentation on clone RRIM 600 in Chachoengsao Rubber Research Centre (RRIT-DOA), under the framework of the project "Towards the improvement of the Rubber Tree Productivity" (RRIT-DOA/Kasetsart University/Cirad). Different strategies in order to alleviate the impact of former constraints are studied. Experiments on reduced tapping frequencies (RTF: d/3 7d/7 or d/4 7d/7) with compensation using ethephon stimulation are conducted. Results confirm that reduced tapping frequencies can reach the same yield per tree (kg/tree/year) or per hectare (kg/ha/year) in comparison with a 1/2S d/2 7d/7 control, leading to an important increase of rubber output per tapper (g/tree/tapping, kg/tapper/day), from +25% to +70% with 1/2S d/3 7d/7 and from +50% to +90% with 1/2S d/4 7d/7, depending on stimulation intensity (number of rounds per year, 2.5% ET concentration). Conditions for a possible and successful implementation of reduced tapping frequencies in Thai rubber plantations are discussed (minimal size of farms, production sharing between tapper and owner...) Although rather difficult to implement in the present Thai rubber fanning context, study on RTF should be continued in order to prepare a future possible shortage of tappers. A new tapping system (Double Cut Alternative or DCA, 2x 1/2S d/4 (t,t) 7d/7) is currently under study in comparison with 1/2S d/2 control. Principle of the DCA system is, in case when RTF cannot be implemented, to optimise higher tapping frequencies by tapping two cuts instead of one. The two cuts, each one tapped in d/4 frequency, are opened on opposite panels (130-1, B0-2) and maintained vertically distant by at least 75-80 cm, in order to minimise competition between their respective latex regeneration areas. The tree is tapped every 2 days, but each cut is tapped every 4 days, increasing regeneration time on each d/4 cut (4 days instead of 2 with 1/2S d/2 7d/7 control). After three years of tapping, DCA system shows, on two different experiments, a significant increase in production (+25-30% for all yield. parameters: kg/tree/year, kg/ha/year, g/tree/tapping and kg/tapper/day) compared to 1/2S d/2 7d/7 control, associated with better latex physiological profiles (latex diagnosis: higher latex sucrose, inorganic phosphorus and reduced thiols). The DCA system does not alter the competitive relationship between trunk growth and rubber production. Compared to reduced tapping frequencies, which only increase output per tapper, DCA system increases both rubber yield and output per tapper in comparison with 1/2S d/2 7d/7 conventional tapping system and therefore appears very promising. (Résumé d'auteur)