Tomoo Hattori

Chemical and biological studies on environmental humic acids: I. Composition of elemental and functional groups of humic acids

Abstract Forty humic acid samples were extracted from various types of soils, including aquatic sediments. To estimate the degree of humification, absorbance coefficients for 1% humic acid solutions at 600 nm () and ΔlogK values were measured. Mean values for decreased in the order: Andisol (A)>Oxisol (O), Mollisol (M), Vertisol (V)>Histosol (H)>Entisol (E), sediment (s), Inceptisol (I). Mean values for ΔlogK increased in the order: A I, E, O, H>M, V>A. A linear correlation was found to ...

Improvements in the method for fractional determination of soil organic nitrogen

Abstract To reinvestigate the experimental conditions for determining various forms of organic nitrogen, known nitrogenous compounds were hydrolysed and steam distilled using Bremners apparatus. The recoveries of amide-N, α-amino-N and hexosamine-N were determined. More than 24 hr were required to complete the hydrolysis of protein and chitin with boiling 6 n HCl. Under these conditions, decomposition of glucosamine occurred and increased with heating time, resulting in an increase of the amide-N fraction. Little glucosamine was decomposed to ammonium-N by hydrolysis with 1 n HCl at 100°C. However, chitin was incompletely hydrolysed to glucosamine under these conditions. In contrast, amide-N was almost completely recovered. The amount of hexosamine-N was determined by subtracting the nitrogen distillable with MgO in the 1 n HCl hydrolysate from the nitrogen distillable with phosphate-borate buffer in the 6 n HCl hydrolysate. Based on these results, improved procedures for determining organic nitrogen are...

Ecological study on the dynamics of soil organic matter and its related properties in shifting cultivation systems of Northern Thailand

Abstract There is a large number of hill people in northern Thailand, who practices shifting cultivation. In order to analyze the soil ecological problems involved in the transition from traditional shifting cultivation to more intensive upland farming, the authors carried out comparative studies on the dynamics of organic matter and its related properties in soils both in the traditional shifting cultivation systems adopted by Karen people and more intensive upland farming practiced by Thai and Hmong people in the area. The contents of organic matter and available N in the surface 10 cm layers of soil from the fields continuously cultivated were lower than those in soils under prolonged fallow (more than 10 y) or natural forest. Based on the rate of soil respiration, the amount of organic matter decomposed within 1 y was estimated to reach nearly 10% of that stored in the upper 50 cm layers of the soil profile in the upland crop fields. These results indicate that the organic matter-related resources mar...

Chemical and biological studies on environmental humic acids II. 1H-nmr and IR spectra of humic acids

Forty humic acids from various types of soils were examined by 1H nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. The 1H-NMR spectra were characterized by peaks which were attributed to aromatic, lactone, methoxyl, and aliphatic protons a, s, and y to aromatic carbon rings. Andisol humic acid showed high percentages of aromatic protons and low percentages of aliphatic and methoxyl protons. Sediment and Inceptisol humic acids showed low aromatic proton and high aliphatic proton percentages. Based on the relationships between the H/C ratio and various proton percentages, it was found that with the progression of humiflcation, aliphatic side chain and methoxyl groups split off, and condensed aromatic rings were introduced into the humic molecules. The characteristic absorption of lignin appeared in the IR spectra of Entisol, Histosol, and Inceptisol humic acids. Entisol, Oxisol, and sediment humic acids showed a strong absorption arising from peptides. Andisol humic acid showed no evidence o...

Selenium in soil humic acid

Abstract The major part of soil selenium was recovered by repeated extractions with 0.1 M sodium hydroxide solution. The soil extract was fractionated into humic and fulvic acids, and the forms of selenium in the humic acid fraction were investigated. Since the major part of the inorganic Se added to the soil extract was recovered in the fulvic acid fraction, selenium in the humic acid fraction was considered to occur in organically-bound forms. Since Se is closely associated with the amino acids in the acid hydrolysate of humic acid, it is suggested that selenium may be present as seleno-amino acids which are the constituents of proteins or peptides contained in the humic acid fraction.

Soil ecological study on dynamics of K, Mg, and Ca, and soil acidity in shifting cultivation in northern Thailand

Abstract Soil degradation caused by excessive land use is presently one of the major constraints on sustainable agriculture in the mountainous area of northern Thailand. In order to obtain basic information about soil fertility problems involved in the transition from traditional shifting cultivation to more intensive upland farming, the dynamics of K, Mg, and Ca, and soil acidity in the farming systems of both Karen and Hmong/Thai peoples were investigated. In the fields that lay fallow for more than 5 y, the soils were highly acidic and poor in exchangeable bases, mainly due to the fact that the fallow vegetation rapidly absorbed inorganic bases (K, Mg, and Ca) in the soils. In the fields both under fallow and cropping within 3 y after the slash and burn practice, the high acidity observed in the soils at the fallow stage seemed to be alleviated by ash input with high alkalinity. The aboveground biomass ranged from 9 to 10 t ha−1 in the 8 y fallow field and the sum of inorganic bases and alkalinity, whi...

Determination of soluble selenium in soils

Abstract Although the selenium (Se) content in a plant is considered to reflect the content in the soil where the plant grows, the chemical form of the Se absorbed by plants from soils has not yet been well documented. Soluble Se dissolved from soils with water or aqueous salt solution is considered to be the main form available to plants and the relation between the Se content of plants and the concentration of soluble Se in soils has been studied (Olson et al. 1942; Asakawa et al. 1977). However, the number of investigations on the method of determination of soil soluble Se is limited. In a previous paper, we reported a method for the determination of trace amounts of Se using high-performance liquid chromatography (HPLC) with fluorescence detection (Yamada et al. 1987). By this method, the total amount of Se in soils could be determined with a high reproducibility and sensibility. Therefore, the application of the HPLC method as a simple and rapid method of determination of soil soluble Se was further ...

Physicochemical properties of the soils associated with shifting cultivation in Northern Thailand with special reference to factors determining soil fertility

Abstract Recently agricultural activity in the mountainous area of northern Thailand has increased and problems relating to soil fertility have arisen. In order to gain basic information about the soil properties associated with shifting cultivation, physicochemical properties of the surface soils (0–10 cm) and subsoils (30–40 cm) were investigated in selected villages in the area. The physicochemical properties of the soils studied are summarized as follows: 1) The soils were rich in organic matter, content of which ranged from 11.4 to 63.3 g C kg−1 in the surface soil. 2) The pH(H2O) of the soils mostly ranged from 5 to 7 and soil acidity was more pronounced in the deeper horizons. In the surface soils, exchangeable Ca and Mg were generally dominant, whereas exchangeable Al was often predominant in the subsoils. 3) Most of the soils showed a medium to fine texture with more than 30% clay. The clay mineral composition was characterized by various degrees of mixture of kaolin minerals and clay mica with, ...

Forms of soluble selenium in soil

Chemical forms of selenium were studied in a solution extracted from soil with water or sodium sulfate solution by means of gel chromatography. When the soil extracts were chromatographed on a Sephadex G-25 column, the selenium in the extracts was separated into high and low molecular-weight fractions. A large proportion of the selenium in both fractions occurred in an organically-bound form and a small amount of inorganic selenium was found in the low molecular-weight fraction. The distribution of selenium on the chromatogram agreed well with that of fluorescamine-reactive substances. It was considered that the selenium in the soil extracts was mainly contained in proteins, peptides or amino acids. In addition, the high molecular-weight fraction containing selenium extracted from an Andosol was found to be a polypeptide with a molecular-weight of about 3,200 and was assumed to be composed of about 29 amino acids.

Nonaqueous titration of functional groups in humic acid

Abstract Humic acid was titrated by sodium methoxide in dimethylsulfoxide using platinum-calomel electrode systems. Adding benzoic acid and phenol as internal standards to humic acid yielded two inflections. The titer at the first inflection point was equivalent to the carboxyl groups whose pKa (H2O) values were less than 7. The difference between the titers at the two inflection points was equivalent to the phenolic hydroxyl groups whose pKa (H2O) values were 7–10. Calculated results for the carboxyl and phenolic hydroxyl groups in humic acid obtained by the nonaqueous titration method agreed closely with those obtained by conventional methods.