LATEX YIELD OF HEVEA BRASILIENSIS POORLY INDICATES SOIL DROUGHT

Predawn leaf water potential, sap flux density or tree transpiration and whole-tree hydraulic conductance are known indicators of soil drought on rubber tree (Hevea brasiliensis). However, these parameters are difficult to access for farmers, in contrast to latex yield which is recorded every day. Hence, the aim of this study was to evaluate the potential use of latex yield as indicator of soil drought in the marginal rainfall areas. The experiment was done during intermittent drought in the rainy season in a representative rubber plantation located in Buriram province, northeast Thailand. The results showed that while the relative transpiration declined by 66% for severe soil drought, the number of rubber sheets per hectare and per tapping decreased slightly by 18% and did not differ for mild drought. Other yield parameters per tapping such as fresh latex per tree or dry rubber content did not differ significantly despite tendencies between severe drought and well-watered period. Finally, the latex yield per tapping does not appear to be a sensitive indicator of soil drought.