To clarify the effects of land use and long-term organic matter application on the dynamics of low-molecular-weight organic acids (LOAs), soil samples were collected from an agricultural site under various organic matter managements and an adjacent Oak forest site. The agricultural site was composed of a chemical fertilizer plot, cattle manure applied plots, a crop residue incorporated plot, and both a cattle manure and crop residue incorporated plot. Formic acid was detected in the soils of all plots at the agricultural site; however, the effect of long-term application of organic matter was less clear. Malic acid was also detected in all soils of the arable lands, and the amount was larger in the organic matter-applied plots than in the chemical fertilizer plot. The amount of citric acid in the arable soils was extremely smaller than in the forest soils. No citric acid was detected in the soils without organic matter application. The total amounts of LOAs were considerably smaller in the arable soils than in the adjacent forest soils, except for the plot where both cattle manure and crop residues had been applied. The land use and long-term application of organic matter practically affected the contents of LOAs in an Andisol, and their effects on the dynamics of nutrients and other constituents should be the subject of future research.
Key words: Land use, long-term organic matter application, low-molecular-weight organic acids, malic acid, water-extractable organic carbon.
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