5:15 PM - 7:15 PM
[AGE34-P07] Composition of Soil Organic Matter and its Evaluation Methods
There are several methods for measuring the amount of organic matter contained in soil, such as total carbon and ignition loss. Since these methods measure soil organic matter as the amount of carbon, they do not provide information on the complexity of the carbon structure of the organic matter or its ease of decomposition. This study will focus on the structure of the compounds in that soil organic matter and compare it with the results of total carbon and ignition loss to evaluate the ease of decomposition, degree of maturation, and newness of the organic matter.
The samples used in this study were paddy soil, forest soil, andosols, and masa soil. The amount of organic matter was measured by ignition loss, and nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC/MS) were used to determine the organic matter contained in the soils. Samples methylated with tetramethylammonium hydroxide (TMAH) were used in the GC/MS measurements. The results were subjected to principal component analysis to discuss the relevance of the data.
The order of magnitude of ignition loss was forest soil, andosols, paddy soil, and masa soil. The NMR results showed large peaks in the spectral region attributed to aromatic carbons in the paddy and forest soils. Peaks were also observed in the spectral regions attributed to aliphatic carbon, methoxyl and carbohydrate carbons, and carboxyl group carbons in the paddy soil, forest soil, and andosols. No significant peaks were observed for the masa soil. GC/MS measurements showed that forest soils had the highest area values for most of the 80 compounds detected. The number of peaks detected in masa soil was lower than in the other soils. The compound results obtained from GC/MS analysis may reflect the amount of organic matter to some extent. Principal component analysis using NMR peak area values indicated that carbohydrate, aliphatic, phenolic, and aromatic carbons were strongly related to the ignition loss carbon, while carboxyl and carbonyl groups were considered to be less related. Principal component analysis using GC/MS, NMR, and ignition loss data with soil type as a variable showed a remote relationship between masa soil and other soils.
The samples used in this study were paddy soil, forest soil, andosols, and masa soil. The amount of organic matter was measured by ignition loss, and nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC/MS) were used to determine the organic matter contained in the soils. Samples methylated with tetramethylammonium hydroxide (TMAH) were used in the GC/MS measurements. The results were subjected to principal component analysis to discuss the relevance of the data.
The order of magnitude of ignition loss was forest soil, andosols, paddy soil, and masa soil. The NMR results showed large peaks in the spectral region attributed to aromatic carbons in the paddy and forest soils. Peaks were also observed in the spectral regions attributed to aliphatic carbon, methoxyl and carbohydrate carbons, and carboxyl group carbons in the paddy soil, forest soil, and andosols. No significant peaks were observed for the masa soil. GC/MS measurements showed that forest soils had the highest area values for most of the 80 compounds detected. The number of peaks detected in masa soil was lower than in the other soils. The compound results obtained from GC/MS analysis may reflect the amount of organic matter to some extent. Principal component analysis using NMR peak area values indicated that carbohydrate, aliphatic, phenolic, and aromatic carbons were strongly related to the ignition loss carbon, while carboxyl and carbonyl groups were considered to be less related. Principal component analysis using GC/MS, NMR, and ignition loss data with soil type as a variable showed a remote relationship between masa soil and other soils.