Investigation of Litter Decomposition and Nutrient Release from Dipterocarpus alatus Roxb. Ex G.Don. as Affected by Soil Moisture in Ecosystem

Kiriya Sungthongwises and Sukanya Taweekij

Background and Objective: The availability of Dipterocarpus alatus in terms of leaf fall per unit area and the degradation to organic and inorganic substances for nutrient cycling by physical, chemical and biological processes have not been found. The purpose of this study was to investigate the rate of D. alatus leaf fall per unit area; percent degradation; nitrogen, phosphorus and potassium content and the amount of nitrogen, phosphorus and potassium released. Materials and Methods: Mesh fabric was installed around the D. alatus tree canopy in Khon Kaen, Roi Et, Yasothon and Mukdahan provinces. Fallen leaves of D. alatus were collected in the hot, rainy and winter seasons. To study the rate of degradation and potential for nutrient release, leaves of D. alatus were packed in a litter bag and placed on the soil surface in various experimental areas. Results: The highest biomass of D. alatus leaves fell in summer at Khon Kaen (483.33 g m^–2), followed by winter in Yasothon (286.67 g m^–2). A higher percentage of D. alatus leaf degradation occurred at the end of the rainy season than at the beginning of the rainy season, causing the maximum release of potassium, 2.89-7.5 kg ha^–1 and the amount of nitrogen released was 0.72-4.93 kg ha^–1 after 4 months. Conclusion: Soil fertility can be increased through organic fertilizer of D. alatus which transforms it into organic matter and inorganic substances in soil. Crops around D. alatus tree can utilize circulating nutrients especially nitrogen and potassium.

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