Sumeth Limmaneethorn, Sayan Sdoodee, and Ibrohem Yeedum

pp. 601 - 613

Abstract

To invegestigate the effects of irrigation on physiological responses and latex yield of rubber trees during the dry season (February-May 2006), 14 year-old rubber trees (RRIM 600 clone), grown at The-Pha Research Station in Songkhla Province were used. An experiment was arranged in a randomized complete block design in 3 treatments and 3 replications. The treatments were as follows: 1) control or rainfed condition (T1), 2) under irrigation regime of 1.00 ETc or crop evapotranspiration (T2) and 3) under irrigation regime of 0.50 ETc (T3). Irrigation caused marked leaf-shedding in T2 and T3, res-pectively, compared in T1. This caused the production of new leaves in T3 and T2 to be about 10 and 20 days, respectively, later than in T1. In the middle of March, leaf density in T2 greatly increased as compared to T3 and T1, respectively. It was found that diurnal changes of leaf water potential and stomatal conductance of the rubber leaves of trees in T1 trended to be lower than those in T2 and T3 during the experimental period. However, there were no significant differences among the treatments. It was also found that the irrigated trees in T2 had significantly
higher latex yields than the trees in T1 by about 18-25%, while there were no significant differences between T1 and T3. There were no significant differences in dry rubber content (DRC) among the three treatments,
the average DRC being about 39%.