Response of low frequency harvesting systems under drier climatic conditions

K.V.V.S. Kudaligama1, V.H.L. Rodrigo1, K.M.E.P. Fernando2 and P.A.J. Yapa
1Department of Biochemistry and Physiology, Rubber Research Institute of Sri Lanka
 2Department of Botany, University of Sri Jayewardenepura, Sri Lanka

The rubber plantations in Sri Lanka lie mostly in the Wet zone (WZ) of the country and in certain regions in the Intermediate zone (IZ). In the IZ rubber plantations are condensed in IL1a agro ecological region. In today context escalating cost of production and inadequate supply of skilled harvesters are among the major issues of natural rubber industry. 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. In LFH, the trees are generally stimulated to obtain yields comparable that of traditional d2 (i.e., tapping a tree once in two days) frequency. Obviously, the stimulation protocol depends mostly on the clone and harvesting frequency. With the higher level of climatic variability resulted from the climate change, prolong droughts are expected adding another factor to be considered in designing the stimulation protocol of LFH systems.

Almost all regions of the island have a potential threat of drought and such possibilities in the IZ are relatively high compared to the wetter parts of the island. Therefore, the present study was aimed atinvestigating the variability in yield in LFH systems, viz. harvesting trees once in three (d3), four (d4) and six (d6) days in drier climates. 

As expected, yield per tree per tapping increased with the decrease in harvesting frequency in both climatic zones. Percentage dry rubber content in latex increased with the decrease in the harvesting frequency. Volume of latex per harvest increased with the reduction of the harvesting frequency. The flow rates of LFH systems in IZ were not up to the expected level resulting insufficient latex volumes.  As a result, ultimate yields given by d4 & d6 systems were less than that of d2 only in IZ. This could be attributed to the lack of soil moisture in IZ to replenish the water taken out from the tree with latex. Therefore, stimulation protocols are to be designed to obtain higher yields in IZ during its wet periods.