EFFECT OF FERTILIZATION AND STIMULATION OF HEVEA BRASILIENSIS TREES ON MINERAL COMPOSITIONS AND PROPERTIES OF PRODUCED LATEX AND RUBBER
This publication reports the mineral composition and the properties of latex and rubber obtained from a fertilizer agronomical trial conducted in Kasetsart University Sitthiporn Kritsadakon Research Station, south Thailand. This trial was designed to study the effect of 4 fertilizer levels on RRIM600 clone trees tapped with the recommended tapping system (S/2 d2) with or without stimulation (ET2.5% 4/y). Latex and rubber characterization was conducted on biannual sampling campaigns from 2014 to 2017. Nitrogen (N) and mineral (P, K, Mg, Ca, Ashes) contents were measured on latex and USS rubber made from this latex. Dry Rubber Content (DRC) and Mechanical Stability (MST) of latex as well as Wallace plasticity (P0), plasticity retention index (PRI) of USS rubber were measured. After 3 agronomical years, latex yield was found to be increased by both fertilization level and stimulation. Concerning N and mineral compositions of latex and USS rubber, no significant effect of fertilization was observed. However, stimulation application was found to be associated with the increase of P content of latex and N, P and Mg contents of USS rubber. Concerning the physical properties of latex (DRC, MST) and USS rubber (P0, PRI), none of these indicators was found to be influenced by either fertilization levels, or stimulant application or their interaction Finally, comparison between latex and USS rubber mineral contents showed that most of P (60%), Mg (82%), and K (89%) was leached in the waste water during the USS making process while the majority of N (34% leached) and the totality of Ca stayed within rubber. The mineral content of the USS process waste water was found to be in the same order of magnitude as the amount brought by fertilizer. Hence, USS process water recycling could be an option to consider.
Keywords: natural rubber, fertilization, mineral export in latex, mineral loss, rubber sheet process, rubber quality