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Horizontal and Vertical Emissions of Methane from Peat Soils

A.V. Jeffary
Department of Crop Science, Universiti Putra Malaysia (UPM), Bintulu Campus, Bintulu, Sarawak, Malaysia

O.H. Ahmed
Department of Crop Science, Universiti Putra Malaysia (UPM), Bintulu Campus, Bintulu, Sarawak, Malaysia

R.K.J. Heng
Department of Forestry Science, Universiti Putra Malaysia (UPM), Bintulu Campus, Bintulu, Sarawak, Malaysia

L.N.L.K. Choo
Soil and Water Management Programme, Strategic Resource Centre, Malaysian Agricultural Research and Development Institute (MARDI), Roban, Saratok, Sarawak, Malaysia

Abstract/ Executive Summary:

Methane emission depends on the rates of methane production, consumption and ability of soil and plants to transport the gas to the soil surface and also within soil particles. The objective of this study was to determine CH₄ fluxes horizontally and vertically from the floor and wall of the pit of a tropical peat soil. The horizontal emissions in the dry and wet seasons were 2.96 t CH₄ ha-¹yr-¹ and 4.27 t CH₄ ha-¹yr-¹, respectively and the vertical emissions were 0.36 t CH₄ ha-¹yr-¹ and 0.51 t CH₄ ha-¹yr-¹^, respectively. The total amount of the horizontal and vertical emissions in the dry and wet seasons were 3.32 t CH4 ha-¹ yr-¹ and 4.78 t CH4 ha-¹yr^-1, respectively. Horizontal emission was higher in the wet season due to an increase in the water table which resulted in an increase of CH₄ emission. Thus, there is a need for direct CH₄ measurement from cultivated peat soils to ensure that CH₄ emission is neither underestimated nor overestimated.

Keywords: Emission, Methane flux, Tropical peatlands, Greenhouse gas

Location: Malaysia Agricultural Research and Development Institute (MARDI) Peat Research Station Saratok, Sarawak, Malaysia

Start Date:

End Date:

Program Area: Physical and Mechanical Properties

Commodity: Land degradation

Objectives:

The objective of this study was to quantify horizontal and vertical CH₄emissions on a drained tropical peat lands cultivated with pineapple.

Methodology:

The study was carried out at Malaysia Agricultural Research and Development Institute (MARDI) Peat Research Station Saratok, Sarawak, Malaysia. MARDI, Saratok has a total area of 387 hectares and located on a logged-over forest with flat topography of 5 m to 6 m above mean sea level (Ahmed and Liza, 2015). Based on the von Post Scale, the peat soils is classified under H7 to H9; well decomposed sapric peat with a strong smell and thickness ranges 0.5 m to 3.0 m (Ahmed and Liza, 2015). The mean temperature of the peat area ranges from 22.1 to 31.7 °C with relative humidity ranging from 61 to 98% (Ahmed and Liza, 2015). The annual mean rainfall of the area is 3749 mm; where in the wet season, the monthly rainfall is more than 400 mm whereas in the dry season is 200.7 mm (Ahmed and Liza, 2015). Methane emission measurements were carried out at 0-5 cm and 5-10 cm peat soil depths, respectively. Measurements of the CH₄ emission were carried out in 10 m x 10 m drained peat soil plots cultivated with pineapple. Methane flux sampling was carried out for 24 hours at every 6 hours interval (between 0600 hr to 0600 hr) and were monitored once throughout the dry (July 2015) and wet (December 2015) period. The horizontal movement of CH₄ emissions from the peat soil surface was measured using the closed chamber method (Norman et al., 1997; Crill et al., 1988). The fabricated I-shaped chamber was gently pressed vertically on the surface of the soil pit at of 3-5 cm depth. The chamber was equilibrated for 30 minutes. The headspace samples of 20 mL were extracted from the chamber every minute for 6 minutes starting at 1 minute using a 50 mL syringe. The extracted gas was then transferred to 20 mL vacuum headspace vials using a disposable syringe needle. Methane concentration was measured using a Gas Chromatography (GC- Agilent 7890A) equipped with a thermal conductivity detector (TCD) (Ahmed and Liza, 2015). The vertical CH₄ movement was measured at 5 cm depth interval (0-5 cm, 5-10 cm), from the surface to 10 cm above water table (saturated zone). The L-shaped chamber was installed horizontally to the wall of the peat soil at 20 cm. The end of the chamber was covered and sealed with steel cap and parafilm, respectively. For each depth, peat soil was manually removed to a suitable working size pit. The open cylinder was left standing for approximately 30 minutes to establish an equilibrium state. The CH₄ sampling and measurement was carried out for 24 hours at every 6 hours (between 0600 hr to 0600 hr). The gas flux was measured in early morning I (06000700), afternoon (1200-1300), evening (1800-1900), midnight (2400-0100), and early morning II (0600-0700) to obtain a 24 hours GHG emission. The gas sampling was carried out once a month from July 2015 to August 2015 for dry season; September and December 2015 for wet season. Thus, the total numbers of gas sampling are 4 times in 4 months. The results were based on the measurement of CH₄ from the five durations using two methods (I-chamber and L-chamber) in the dry and wet seasons. The values of CH₄ emitted were averaged and converted into units of t ha-¹yr^-1. The CH₄fluxes were then calculated using the following equation (Zulkefli et al., 2010; Widen and Lindroth, 2003; IAEA, 1992).

Flux= [(CO₂/CH₄) dt] X PV ART′, where (CO₂/CH₄₎/(dt) is the evolution rate of CO₂/CH₄ within the chamber headspace at a given time after which the chamber were placed into the soil, P is the atmospheric pressure, V is the volume headspace gas within the chamber, A is the area of soil enclosed by the chamber, R is the gas constant, and T is the air temperature.

Statistical analysis Analysis of variance (ANOVA) was used to detect treatment effects whereas treatments means were compared using Duncan’s New Multiple Range Test (DNMRT) at P ≤ 0.05. The statistical software used for this analysis was Statistical Analysis System (SAS) version 9.3.

Source of Information: J Bangladesh Agril Univ 17(3): 359–362, 2019 ISSN 1810-3030 (Print) 2408-8684

Article Link (Online Journal): https://doi.org/10.3329/jbau.v17i3.43212

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In tropical peat soils cultivated with pineapples, horizontal emission of CH₄is higher than vertical emission. However, to avoid underestimation of CH₄emission from pineapples cultivation on tropical peats, both horizontal and vertical emissions of this gas must be considered regardless of season.

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