Evaluation of CH4 Emission in Two Paddy Field Areas, Khonkaen and Ayutthaya, in Thailand

Pongsathorn Sukdanont,Noppol Arunrat,Ryusuke Hatano,Suphachai Amkha

doi:10.3390/agriculture11050467

Pongsathorn Sukdanont, Noppol Arunrat + Show 2 more

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https://doi.org/10.3390/agriculture11050467

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Abstract

It is well known that submerged soils emit high levels of methane (CH4) due to oxygen deprivation and free iron oxide causing a quick reduction. However, there are other soil properties that control the reduction processes in soil, especially the amount of soil organic carbon (SOC). This study aimed to investigate the major factors controlling CH4 production potential (CH4PP) in Thai paddy fields. Two provinces, Ayutthaya, a clay soil region, and Khonkaen, a sandy soil region, were selected to represent a wide range of soil textures. Soil characteristic analysis pre- and post-incubation, and weekly gas detection in an incubation experiment over two months, was conducted. Stepwise multiple regression analysis was employed to analyze major soil factors controlling CH4PP. For the regional prediction of CH4PP, a map dataset of Ayutthaya and Khonkaen by the Land Development Department, Thailand, and a soil texture map (with intersected point data using the soil property map in ArcGIS) by OpenLandMap, were used. CH4PP was correlated with 1:10 pH, Fe2+, and water-soluble organic carbon (WSOC) measured after incubation. Although CH4PP showed no significant correlation with any soil properties measured before incubation, CH4PP was correlated with SOC, 1:10 electrical conductivity (EC), exchangeable ammonium (ExNH4), and sand content. It was thought that SOC and ExNH4 were related to organic matter decomposition, 1:10 EC was related to SO42− reduction and sand content was related to free oxides. Predicted regional CH4PP was similar in Ayutthaya and Khonkaen, although SOC, ExNH4 and 1:10 EC was higher, and sand content was lower in Ayutthaya than in Khonkaen. In both regions, the distribution of CH4PP corresponded to SOC, and CH4PP was lower with lower sand content and higher 1:10 EC. In clayey Ayutthaya, higher CH4PP was observed in the area with higher ExNH4. This indicates that soil properties other than soil texture and SOC influence CH4PP in the paddy fields in Thailand.

Highlights

IntroductionCauses and mitigation issues related to global warming have become controversial
In recent decades, causes and mitigation issues related to global warming have become controversial
For the soil properties measured before incubation, Ayutthaya was significantly greater than Khonkaen (p ≤ 0.05) in 1:10 ECBI (10.69 and 1.97 mS.m−1), soil organic matter (SOM) (4.26% and 1.27%), soil organic carbon (SOC) (2.46% and 0.74%), ExNH4(BI) (17.07 and 12.38 mg·kg−1), ExK, ExCa, ExMg, ExNa, Total N, cation exchange capacity (CEC), SO42−-SBI, and silt

Summary

Introduction

Causes and mitigation issues related to global warming have become controversial. Paddy fields are an important source of atmospheric CH4, as flooded conditions are preferable for proper rice growth [2,3]. Rice cropping is considered to account for 5 to 20% of total CH4 emission from anthropogenic actions [4]. Paddy fields in Thailand cover almost half the total agricultural land and are mostly located in the central and northeastern parts of the country. These regions have different soil types, with clayey soil in the central region, and sandy soil in the northeastern part [5,6]. Rice cultivation in Thailand was ranked as the fourth highest global CH4 emitter, contributing an average of 1756.6 Gg CH4 between 2010 and 2017 [7]

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