| Summary: | Although lowland area is not suitable for rubber production, rubber trees are currently extended into abandoned paddy
fields. This study investigated rubber growth, soil properties and leaf nutrients of immature rubber trees planted in lowland
and upland plantations. Nine soils (0-30 cm depth) in both poor and good productive lowland and upland plots from three
districts in Songkhla province were sampled for some physical and chemical analysis and leaf samples were also performed
for nutrient analysis. Growth of rubber trees was recorded. Results showed that soil in the lowland had finer texture compared
with the upland soil, resulting in tendency of higher organic matter, total N and CEC. In addition, high DTPA Mn and soil
mottles are generally found in a profile of the lowland soil. However, immature rubber trees planted in the good productive
lowland plot grew as similar as in the upland soil. Whereas, in the poor productive plot, rubber growth was limited and
concentrations of leaf N, P and K tended to be lower than those in the upland soil, in contrast to leaf Mn. These findings
revealed that soil mottles within 0-30 cm are markedly indicator of limitation of the lowland for rubber cultivation.
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