Department of Biochemistry and Physiology, Rubber Research Institute, Sri Lanka 2 Department of Botany, University of Sri Jayewardenepura, Sri Lanka * email@example.com, Tel-++ 94 34 2247426, Fax- ++ 94 34 2247427 Abstract
Escalating cost of production (COP) and inadequate supply of skilled harvesters are among the major issues that natural rubber industry face today. Low frequency harvesting (LFH) systems of which trees are tapped in a lesser frequency than once in two days, are considered to be one of the solutions to overcome these issues. With the focus given to expand rubber in drier climates, the present study was aimed to investigate on the yield response of LFH systems, viz. harvesting trees once in three (d3), four (d4) and six (d6) days in the intermediate zone (IZ) with the stimulation protocols developed for the wet zone (WZ). With the decrease in harvesting frequency in IZ, yield per tree per tapping (GTT) increased, however yield per tree per year (YPT) decreased. No such declines were observed in WZ. Stimulation had no negative impact on percentage dry rubber content in latex (%DRC) or incidence of Tapping Panel Dryness. Whilst only the S/2 d3 system is acceptable for IZ in the present form, stimulation protocols are to be revised in other LFH systems. Bark consumption was reduced significantly by LFH resulting in several long-term beneficial effects. Effect of stimulation on latex physiology is also discussed. Keywords: Climate change, Ethephon, Hevea, Low frequency harvesting, Rubber
1. INTRODUCTION Being the second largest plantation crop in the country, rubber (Hevea brasiliensis) covers ca. 122,000 ha and produces ca. 129million kg of raw rubber (ref). More importantly, it provides ca. 500,000 direct and indirect employments. The total export earnings from raw rubber and end products in 2008 was about Rs. 72 billion (Anon, 2008a, Anon, 2008b). The rubber plantations in Sri Lankan lie in almost the Wet zone (WZ) of the country and certain regions in the Intermediate zone (IZ). The demand for rubber among the farmers in the IZ is escalating rapidly due to the poor turnover from the cash crops faming in those areas. The IZ, running between the Wet and Dry zones demarcates the area, which receives a mean annual rainfall between 1,270 - 2,540 mm with considerable dry spells (Wjesekera, et al, 2004) whilst the annual rainfall in WZ is over 2,500 mm. During the month of April, temperature in IZ can rise up to about 35 °C, however, that in between late November to mid February period is lower than the rest of the year (Anon, 2009). A uniformly distributed rainfall with about 1650 - 3000 mm per year is known to be ideal for the cultivation of rubber. In the areas with an average temperature in the range of 23 – 28 oC and altitude less than 200m above sea level, rubber tree performs well in establishing, growing and yielding (Yogaratnam, 2001). High relative humidity (ca.80%) and radiation level (ca. 2000 hrs/year) influence the plant growth and yield (Pushpadas & Karthikakutty Amma, 1980, Rao & Vijayakumar, 1992). Although IZ receives a considerable amount of rainfall, the un-uniform pattern makes stressful conditions to the trees. Longer dry spells during wintering period create adverse effects on both growth and yield. Traditionally, the rubber tree is tapped with S/2 d2 (i.e. half spiral cut tapped once in two days) harvesting system. Tapping once in three days (S/2 d3) is recommended in Sri Lanka with 2.5% Proceedings of the 15th International Forestry and Environment Symposium, 26-27 November 2010. Published by Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka.
Ethephon with 4-5 stimulation rounds per year (Nugawela, 2001). Harvesting is considered to be the most...