The Potential of Fruits Orchard Cultivation in the Mekong River region : Comparative Case Study of Mangosteen Orchard Microclimate and Root Zone Soil Water Status in the Mekong River Region, Bueng Kan and Southern Region, Nakhon Si Thammarat Province

Abstract

Since 2015, the Thai government has been driving policy on control nationwide para rubber tree plantation due to the falling global rubber prices. Fruit trees farming is an alternative policy to replace rubber trees. This study evaluated the potential in growing fruit crops in region along the Mekong River. The microclimate data and soil water of mangosteen root zone data were analyzed to compare Bueng Kan with the southern Province, Nakhon Si Thammarat, the largest site for mangosteen production. During 2018–2020, Bueng Kan showed up a critical 6–month rainfall shortage (October–March) causing the severe dryness of soil profile 0–100 cm as soil matric potential (y_m) of –100 to –200 kPa. Air vapor pressure deficit (VPD_air) was higher of 2–6 kPa inducing stomata closure and limiting leaf photosynthesis and transpiration. The optimal hour for photosynthesis was low of 1–4 hours per day throughout drought period covering the flowering to fruit set stages. Whereas rainy period (April–September) the optimal hour was high of 4–10 hours per day covering the fruit development to harvest stages. For Nakhon Si Thammarat, the annual rainfall was over 2,000 mm with higher rainfall frequency. However, the continual rainfall limited average radiation intensity below 500 µmol m^–2 s^–1 and maximized relative humidity (RH) to 100% almost every day. This condition limited the optimal hours for photosynthesis to be 2–6 hours per day throughout the year. According to the favorable climate and soil water in rainy period, the region along the Mekong River, Bueng Kan is remarked to be the potential site for growing mangosteen to replace para rubber tree