Kyoichi Kumada

THE INFRA-RED SPECTRA OF HUMIC ACIDS

Abstract It is well krown that many investigations have been presented on the visible and ultraviolet absorption spectra of soil humic acids, and they contributed greatly to our knowledge on the nature of humus. On the other hand, there have been very few works on the infared spectra of humic acids, though it is expected that they would give us useful information on their nature, especially furctional groups.

An x-ray diffraction study of humic acids

A, Rp and P type humic acids and certain related materials were subjected to X-ray diffraction analysis. In general, the soil humic acids exhibited y- and (002)-bands. A and Rp type humic acids showed (002)- and y-bands, respectively. P type humic acid exhibited y- and (002)-bands, with the former predominating with regard to the latter. The (002)-band of A type humic acids was further analyzed using the Fourier transformation method. The number of layers stacked parallel to each other was 9 on the average. The most commonly found stacking units consisted of 2 and 3 layers. The average maximum number of layers per stack was 2.66. The weight percent of stack per humic acid was up to 32. In the case of Sochicken-1 humic acid (A type) extracted from Kuroboku soil, the presence of layer stacking was confirmed by transmission electron microscopy. Based on these results, the structure of humic acids is discussed.

ELEMENTARY COMPOSITION AND ABSORPTION SPECTRA OF HUMIC AND FULVIC ACIDS

Elementary composition and absorption spectra of humic acids (HAs) and fulvic acids (FAs) obtained from 4 Canadian and 2 Japanese soils were determined, and the relationships between these 2 properties were discussed. In this study, FA refers to the PVP adsorbed, i.e. coloured substances in what has been designated, in previous reports, as FA. In 3 soil samples, FA was divided into the acid (pH 1.0)-precipitable FA1 and non-precipitable FA2 fractions. 1. In the case of HAs, some correlations were observed between the carbon content and hydrogen content or C/H ratio. The hydrogen and nitrogen contents of the FA and FA1 samples tended to be higher while those of the FA2 samples tended to be lower than those of HAs obtained from the same soils. In all cases, conspicuous differences in the elementary composition were found between the FA1 and FA2 fractions. 2. The absorption spectra (log E vs. λ curves, in 0.1 N NaOH) of 5 out of 17 samples of HAs and FAs showed absorption bands due to the dissociation of the...

Experimental Studies on the Behavior of Fine Organic Particles and Water-Soluble Organic Matter in Mineral Soil Horizons

The following three series of experiments were carried out to analyze the behavior of the fine organic particles and water-soluble organic matter (FWOM) in mineral soil horizon. 1) The FWOM suspension obtained from decayed Crypfomeria japonica leaves was passed through the columns filled with three different samples of mineral soil horizons and sea sand, and C and N contents were determined for the effluent, and the soil samples and sea sand after elution. 2) The water-soluble organic matter fraction separated from the FWOM was examined for its adsorbability on three different soil samples. 3) The freeze-dried FWOM was incubated with the soil samples and sand at 50% of maximum water holding capacity for 2 months at 30°C, and analyzed for C decomposition rate and humus composition. The results obtained are summarized as follows. 1) Column experiment. The FWOM penetrated into soil columns by water percolation, while coarse organic particles accumulated on the surface of the columns. The FWOM which penetrate...

Changes in Soil Organic Matter and Nitrogen Fertility during the Slash-and-Burn and Cropping Phases in Experimental Shifting Cultivation

At the experimental field for the study of shifting cultivation set up in the forest of Iriomote Island in Okinawa, changes in pH, organic matter, and nitrogen fertility of soils after forest clearing by burning and during crop cultivation were investigated. The soils were sampled at six periods, I (before forest clearing), II (immediately before burning), III (immediately after burning), IV, V, and VI (10, 20, and 30 months after burning). Tilled and nontilled and other treatment plots were laid out, and cassava was grown twice. Soil pHs rose from periods I to III or IV, and then decreased. Carbon and nitrogen contents, the amounts of mineralizable nitrogen and nitrogen mineralization percentages decreased during cultivation. The amounts of humic and fulvic acids increased from periods I to II and decreased afterwards. The increase in NH4−N due to the soil-burning effect was observed. The changes in the above-mentioned parameters during the cultivation period were greater for the first layer (0–5 cm) tha...

Elementary composition of humic acids

Abstract The author made a study of the elementary composition of various humic acids; L and SrL humic acids used in the previous report1), and two lowmoor humic acids.

SEVERAL PROPERTIES OF HUMIC ACIDS

Abstract In the preceding paper1), it was shown that the elementary composition of soil humic acid changed regularly with the progress of humification. Afterwards, the author conducted several experiments on the base exchange capacity, the content of hydrolysable nitrogen, the resistance to oxidizing reagent, the electrolyte coagulation and X-ray analysis of various humic acids. These experimental resu1ts will be given in this report.

The infrared absorption spectra of soil components

Abstract In the preceding paper (1), the authors had determined the infrared absorption spectra of humic acids obtained from various soils of different origin, and concluded that they were, according to their infrared characteristics, classified into four groupes, i.e., A,B,Rp, and P types. After that, the authors conducted some experiments of the infrared spectra of soil components in order to get some information on the nature of so-called humin, and forms of soil clay and clay humus complex. The infrared spectra of silica, sesquioxides, clay minerals and humates of aluminium, iron and calcium were also determined for comparison. These experimental results will be given in this paper.

On artificial humic acids

Abstract I. Absorption Spectra of Some Artificial Humic Acids It is a well known fact that numerous dark brown or black and amorphous substances cap be produced from organic compounds by purely chemical processes. Some of them are called artificial humic acids, and have been used as a model of soil humic acids by many workers. But it is doubtful whether such artificial humic acids are considered to be a model of soil humic acids, even if there can be found any similarities in their properties. However it may be an useful method for the study of humus formation to compare artificial humic acids with soil humic acids, and to make efforts to find a good model or to prepare artificial humic acids comparable to soil humic acids under laboratory conditions. For this purpose, first of all, the author prepared artificial humic acids from glucose, hydroquinone and lignin, and their absorption spectra were determined.

A model for a type humic acid

Abstract In the preceding papers (1,2,3,4), the author studied some chemical properties of soil humic acids, and compared various so-called artificial humic acids with soil humic acids in respect to their absorption spectra and stabilities. According to these experimental results, it is Presumed that soil humic acids, especially A type, must contain not only benzene ring, but also condensed aromatic rings as their structural units.