Showing papers in "Soil Science and Plant Nutrition in 1978"
TL;DR: In this article, the relationship between elementary compositions and types of humic acids or the "degrees of humification" were studied statistically using 39 humic acid prepared from various types of soils.
Abstract: Relationships between elementary compositions and types of humic acids or the "degrees of humification were studied statistically using 39 humic acids prepared from various types of soils. Mean values of C%. H%. N%, 0%, H/C, N/C, and O/C of the different types of humic acids (A. B. Rp(l), Rp(2). and Po) were compared. The elementary compositions of various types of humic acids were proven by variance analyses to be significantly distinct. Linear regression analyses of C%, H%, N%. 0%, H/C, N/C, or O/C on RF or AlogK values were also carried out on 35 humic acids excluding the P+~+++ type humic acids. The linear associations were found to be significant between C%-RF (5% level), H%-RF, H%-▵logK, H/C-RF and HIC-▵logK (0.1% level), N/C-RF(O.1% level). N%-RF(l% level), N%-▵logK N/C-▵logK(5% level), and ▵logK (1% level), while no significant relationship was found with regard to C%;-▵logK, 0%-▵logK (both 5% level) and O/C-RF and O/C-▵logK (l0% level). Carbon and oxygen contents of humic acids may be ap...
139 citations
TL;DR: In this paper, the levels of alcoholic and phenolic hydroxyl, methoxyl, carboxyl, and carbonyl groups of 33 to 38 humic acids obtained from various types of soils were determined to analyze the relationships between the amounts of these functional groups and the degree of humification or the types of soil.
Abstract: The levels of alcoholic and phenolic hydroxyl, methoxyl, carboxyl, and carbonyl groups of 33 to 38 humic acids obtained from various types of soils were determined to analyze the relationships between the amounts of these functional groups and the degree of humification or the types of soils. The amounts of various oxygen-containing functional groups examined were all proven to be significantly different among the various types of humic acids by analyses of variance. During humification. generally, the carboxyl and carbonyl groups increased while alcoholic and phenolic hydroxyl and methoxyl groups decreased. Linear and logarithmic regression analyses of carboxyl group contents on RF values (optical density of the alkaline solution of humic acids at 600 nm) gave very significant positive correlations. The carboxyl group contents of Rp type humic acids and humic acids from calcareous soils were largely distributed in the upper side of the regression curve. The carbonyl group contents showed a very ...
93 citations
TL;DR: In this article, the intact nodules attached to the upper part of soybean roots were exposed to 15N2 and the incorporation of 15N into various soluble nitrogen constituents was investigated.
Abstract: The intact nodules attached to the upper part of soybean roots were exposed to 15N2 and the incorporation of 15N into various soluble nitrogen constituents was investigated. Results indicated that ammonia, a primary product of N2 fixation, was located in more than two compartments. Ammonia reduced from N2 gas seemed to be incorporated firstly into glutamine especially amido-group nitrogen. Newly fixed nitrogen was secondly incorporated into glutamic acid and alanine in this sequence. These results suggested that fixed ammonia was assimilated by glutamine synthetase/glutamate synthase pathway. Turn-over rate of allantoin plus allantoic acid and serine was relatively high, although apparently these compounds were not primary products of newly fixed ammonia. 15N content of allantoin was always higher than that of allantoic acid. 15N incorporation to aspartic acid and asparagine was relatively slow, especially in early period. In bacteroid fraction there is much amount of ammonia comparing with other...
83 citations
TL;DR: Tomato plants were solution cultured with and without silicon, and Si deficiency symptoms were observed in the first bud flowering stage when the tomato plants had been cultured in a silicon-free solution; however, normal growth was observed in a solution with 100 ppm SiO2.
Abstract: Tomato plants were solution cultured with and without silicon, and Si deficiency symptoms were observed in the first bud flowering stage when the tomato plants had been cultured in a silicon-free solution; however, normal growth was observed in a solution with 100 ppm SiO2. To induce Si deficiency symptoms, it is necessary to culture the plant in a silicon-free solution under favorable conditions for the growth of tomato plant. Select the most suitable cultivar for the environmental conditions. Optimum temperatures with differences for day and night, high light intensity, sufficient aeration, and low planting density are key points in the development of a Si deficiency. Symptoms of Si deficiency may be summarized as follows: 1) The deficiency symptoms appear after the first bud flowering stage. 2) The leaflets of the new leaves showed malformations such as curving to the outside, warping, hardening, and sometimes thickening. 3) The growing poillt at the top was retarded in development, but did no...
78 citations
TL;DR: In this article, the contribution of organic matter produced in the flood water to the fertility of a rice soil, the primary productivity and the algal biomass therein were examined throughout one crop.
Abstract: To assess the contribution of organic matter produced in the flood water to the fertility of a rice soil, the primary productivity and the algal biomass therein were examined throughout one crop. Primary productivity was estimated from the diurnal curve of dissolved oxygen. Just after transplanting, an algal bloom developed due to fert,ilizer or ploughing or both. After submerged weeds occupied the whole paddy no distinct algal growth was found. At the ripening stage, the rice plant canopy suppressed the growth of aquatic plants. Benthic algal biomass did not change much throughout the crop period. The standing crop of algae ranged from 2 to 114 kg/ha by fresh weight, while the maximum standing crop of submerged weeds (Najas sp., Chara sp.) was 400 kg/ha by dry weight. The primary productivity of the flood water community was high (0.6-3.3 g 0 1 m-2day-l) and equivalent to productivity values in eutrophic lakes. The total gross primary production of the flood water community during the cropping p...
70 citations
TL;DR: In this paper, the occurrence of imogolite in a number of Scottish soils developed on parent materials not affected by recent volcanic activity has been investigated, but no conclusive evidence of its presence has been presented.
Abstract: Imogolite, a hydrous aluminium silicate with a fibrous morphology and a well defined structure (3), has, since its discovery by YOSHINAGA and AOMINE in 1962 (12), been found as a weathering product of pyroclastic materials in a number of localities throughout the world (4, 9, 13, 14). However, the precise mechanism by which this mineral is formed has not been established. Material with the morphology of imogolite has been observed by electron optical techniques in the clay fraction of podzolic soils developed on dune sand (1) and on a quartz parent material (6), but no conclusive evidence of its presence has been presented. This note records the occurrence of imogolite in a number of Scottish soils developed on parent materials not affected by recent volcanic activity.
55 citations
TL;DR: In this paper, the authors studied the uptake and assimilation of inorganic N in young rice plants with labelled N (N-15) and showed that low light intensity resulted in a lower proportion of insoluble N in roots and shoots, and the incorporation of labelled N into the insoluble fraction (proteins, nucleic acids) was higher in plants fed with NH4 +-N than in those fed with NO3.
Abstract: Uptake and assimilation of inorganic N in young rice plants has been studied with labelled N (N-15) Depletion of the plants' carbohydrate content, obtained by a preceding dark period, resulted in a drastic reduction of NH4 +-N uptake Plants exposed to low light intensity showed diminishing NH4 +-N uptake rates as compared with plants exposed to full light intensity, the latter showing constant NH4 +-N uptake rates during the whole experimental period The percentage of labelled insoluble N in total labelled N was not significantly affected by a preceding dark period, whereas the low light intensity resulted in a lower proportion of insoluble N in roots and shoots The incorporation of labelled N into the insoluble fraction (proteins, nucleic acids) was higher in plants fed with NH4 +-N than in those fed with NO3 - The uptake of NH4 +-N was not significantly affected by NO3 -, whereas the NO3- uptake rate was considerably reduced in the presence of NH4 +-N Low energy status of plants affected
52 citations
TL;DR: A technique to estimate the quantity of N2 fixed in the flooded water on the rice field and in association with the rice plant is described in this paper, where removal of the flood water and the surface soil and addition of fresh water eliminated the bulk of the N2 fixation associated with the blue-green algae.
Abstract: A technique to estimate the quantity of N2 fixed in the flooded water on the rice field and in association with the rice plant is described. Removal of the flood water and the surface soil and addition of fresh water eliminated the bulk of N2 fixation associated with the blue-green algae. After the algal activity was eliminated, the acetylene reduction activity was higher in planted soils than that in fallow soils. Some N2 fixation is, therefore, associated with the presence of the rice plant. In an IRRI unfertilized flooded rice field, algal acetylene reduction activity was estimated to be 200 mmol C2H4/m2 in the wet season (163 days) and 300 nunol C.H,/ml in the dry season (168 days). Acetylene reduction activity associated with the rice plant (IR26) was calculated to be 90 nunol C2H4/m2 in wet season (163 days) and 50 mmol C2H4/m2 in the dry season (168 days, IR36). Similar rates were obtained at a second site in the Philippines. N2 fixation was associated with both the stems and roots of wetl...
50 citations
TL;DR: Rice, corn, sorghum, mungbeans, and cowpeas were continuously grown on the same land at 2- to 6-week intervals between crops to determine effects on yield, and biological agents were involved in growth inhibition of rnungbeans and dryland rice.
Abstract: Rice, corn, sorghum, mungbeans, and cowpeas were continuously grown on the same land at 2- to 6-week intervals between crops to determine effects on yield. Decline of growth and yield occurred during continuous cropping. Dryland rice, mungbeans, and cowpeas were affected most, corn slightly, and sorghum was not visibly affected. Growth inhibition in dryland rice and mungbeans occurred after one or two crops; growing the same crop in rapid succession resulted il1low grain yields. The persistence of inhibitory effects was indicated. One crop rotation or 5 months of fallow removed only a part of the harmful effects. The causal agent appears to have a specific affinity to the host crop. Root residues of the previous crop may serve as a source of the causal agent for the subsequent crop. Biological agents were involved in growth inhibition of rnungbeans and dryland rice. In mungbeans, the inhibitory effects appeared to be directly dependent on microorganisms. It appeared that microorganisms were not t...
45 citations
45 citations
TL;DR: The returning of sewage sludges or animal manure into crop fields is considered to be one of the most effective methods in reducing the use of industrially produced fertilizer, which consumes high cost oil energy, as well as utilizing the mineral nutrients in the wastes for crop production.
Abstract: The returning of sewage sludges or animal manure into crop fields is considered to be one of the most effective methods in reducing the use of industrially produced fertilizer, which consumes high cost oil energy, as well as utilizing the mineral nutrients in the wastes for crop production If this route of mineral cycling is developed, careful examination is needed to protect crop lands and human environment from any possible pollution problem Sometimes sewage contains a high amount of heavy metals (2) and usually contains a large amount of nitrogenous compounds, which are mostly microbial proteins and easily mineralized into ammonia or nitrate The heavy metals and inorganic nitrogen (mainly nitrate) may cause a pollution problem to our environment, if their concentration in the soil is high High nitrate content of vegetables is sometimes a result of a high concentration of nitrate in soil (7) The run-off of inorganic nitrogen from agricultural lands is considered to be one of the causes of
TL;DR: In this article, the mechanism involved in the reaction of dodecylbenzenesulfonates (ABS and LAS) with soil colloids was studied in 19 soils.
Abstract: In order to elucidate the behavior of surfactants in soil ecosystems, the mechanism involved in the reaction of dodecylbenzenesulfonates (ABS and LAS) with soil colloids was studied in 19 soils. Soil colloids, especially sesquioxides, were capable of adsorbing considerable quantities of dodecylbenzenesulfonates. ABS adsorption on soils was strongly affected by pH, and was scarecely affected by Cl- but appreciably by SO4 2- and H2PO4 -. ABS was adsorbed by the ligand exchange on soil colloids. ABS adsorption on clay surfaces follows the Langmuir isotherm. However, “intermolecular associations” occurred with increasing ABS concentration. Within certain levels of adsorption, ABS-c1ay complex became hydrophobic and floated to the liquid surface. The degradation of ABS was depressed by the addition of soil, while a difference among soils was slight. On the other hand, LAS degradation rate differed from one another depending upon the soil. LAS adsorbed on soils containing large amounts of allophane and...
TL;DR: In this article, Kumada el al. analyzed humus composition by the modified Waksman method and found that the extraction ratio of soluble humus, amounts of humic acid and fulvic acid, and PQ value tended to increase with some exceptions.
Abstract: Samples described in the previous paper were analyzed for humus composition by the method of Kumada el al,, elementary composition of humic acids, nitrogen distribution among humic acid, fulvic acid, and humin, and organic matter composition by the modified Waksman method. The samples obtained by physical fractionation from each horizon of Higashiyama soil were as follows: f1 and f2 from the L layer, f1, f2 and f3 from the F layer, f1 f2, sand, silt, and clay fractions from the H-A and A horizons. With the progress of decomposition, the following tendencies were rather clearly observed. The extraction ratio of soluble humus, amounts of humic acid and fulvic acid, and PQ, value tended to increase with some exceptions. The degree of humification of humic acid proceeded. Most humic acids belonged to the Rp type, but those of the clay fractions belonged to the B type. As for the elementary composition of humic acid, transitional changes from the Lf1 to the clay fraction of the A horizon were observed...
TL;DR: In this article, a pot experiment with Maahas clay soil covered three consecutive crops and showed that one cycle of alternate wet and dry soil preparation for 20 days before transplanting rice improved soil nitrogen availability and plant uptake of fertilizer nitrogen.
Abstract: A pot experiment with Maahas clay soil covered three consecutive crops. After uniform growth of the first crop, the soils were subjected to different moisture conditions during the dry season. Prolonged drying before wet season flooded rice stimulated increased release of mineral nitrogen but moistening of the dry soil for a dryland crop or by occasional rain during the dry season reduced nitrogen use from the soil in the next wet season. One cycle of alternate wet and dry soil preparation for 20 days before transplanting rice improved soil nitrogen availability and plant uptake of fertilizer nitrogen. The initial growth of rice was retarded after flooding the previously moist dryland or dried soil, but not in the continuously flooded soils. Losses of applied nitrogen were small in continuously flooded soils and were greater in the previously moist dryland and dry treatments. Uptake of soil nitrogen, however, was much higher in the air-dried soil treatment and in the dry with alternate wet and dr...
TL;DR: In this paper, the authors investigated the relationship between the change of humus property and time factor, the humus composition in the buried humic horizons with the age from 28,000 years B.P. to the present, according to the method presented by Kumada et al.
Abstract: To investigate the relationship between the change of humus property and time factor, the humus composition in the buried humic horizons with the age from 28,000 years B.P. to the present was studied, according to the method presented by Kumada et al. (7). The fH decreased with the elapse of time and in case of most of humus in the buried humic horizons with the age over 10,000 years, the fH became lower than 40 and were in the form of so-called ‘combined’ humus. When 3,000-4,000 years have passed since the surface soil buried, the humic acid first moved . to ‘combined form.’ Second, after over 10,000 years, the fulvic acid moved to ‘combined form.’ The humification of ‘free’ humic acid proceeded with the elapse of time till around 5,000 years but of 'combined' humic acid till around 7,000 years. Both the humification-degree of ‘free’ humic acid after around 5,000 years and of ‘combined’ humic acid after around 7,000 years decreased. The humification-degree of ‘free’ and ‘combined’ humic acid fro...
TL;DR: In this paper, four long-term experimental plots (Umbric haplaquept) with different fertilizer treatment at Cent. Agric. Exp. Sta. in Konosu City, Saitama Prefecture, were used for the sites of investigation.
Abstract: The 4 long-term experimental plots (Umbric haplaquept) with different fertilizer treatment at Cent. Agric. Exp. Sta. in Konosu City, Saitama Prefecture, were used for the sites of investigation. The 4 plots were NF (applied with no fertilizer), IF (applied with inorganic fertilizers), GM (applied with green manure and CaCO2), and OM (applied with manure and inorganic fertilizers). Flooded water, floating weed, upper (0-2cm) and lower (2-10cm) parts of Apg horizon and rhizosphere were collected from each plot before flooding, during flooding, and after drainage. These samples were analyzed for N2-fixing activity by acetylene reduction method, pH, Eh, and contents of Fe2+, NH4 +, chlorophyll-type compounds, and water-soluble carbohydrates. The N2-fixing activity of all samples showed almost the same pattern of change with time: very low before flooding, rapidly increased after flooding, the maximum value at the maximum tillering stage of rice plant, declined afterwards and reached a very low value ...
TL;DR: In this article, the uptake and transport of cadmium were studied using zinc deficient rice plants and the results showed that these plants absorbed and transported more rapidly than normal rice plants.
Abstract: The uptake and transport of cadmium were studied using zinc deficient rice plants. As a result, these plants absorbed and transported cadmium more rapidly than normal rice plants. A zinc deficiency might bring about physiological changes which significantly increase the cadmium accumulation in the roots and its transport into the shoots.
TL;DR: In this paper, the adsorption of Zn, as compared with Mg, on two mineral soils, which differed in their major cation-exchange materials and with and without Ca-saturation, was measured in the presence of free CaCl2.
Abstract: The adsorption of Zn, as compared with Mg, on two mineral soils, which differed in their major cation-exchange materials and with and without Ca-saturation, was measured in the presence of free CaCl2. The adsorption of Zn as well as Mg occurred on cation-exchange sites. The Zn adsorption data conformed to a two-term Langmuir equation. The presence of two kinds of adsorption sites and their numbers and bonding energies were deduced. However, the Langmuir approach was not adopted on the basis of comparison between the total number of the adsorption sites for Zn deduced and the CEC of the soils. As an alternative approach, the selectivity coefficient as defined by the equation: was calculated for each adsorption equilibrium and plotted against the amount of Zn adsorbed. This [Zn]soil plot was used to estimate the capacities of the soil to adsorb Zn with specified affinities. The value varied between 1 and 1,000, whereas the corresponding value varied only between 0.5 and 1. The value was dependent u...
TL;DR: In this article, soil profiles with different vegetation, developed on igneous rock-derived areas in Northern Kyushu have been sampled at 13 locations and analyzed for total Hg with a flameless atomic absorption spectrometer.
Abstract: Soil profiles with different vegetation, developed on igneous rock-derived areas in Northern Kyushu have been sampled at 13 locations and analyzed for total Hg with a flameless atomic absorption spectrometer. The associated parent rock was also analyzed. The Hg levels of each rock sample were too low, not exceeding 10 ppb, to exert a significant effect within the profiles on the total Hg content. The Hg content was generally higher in the soil than in the underlying rock, irrespective of the depth of the horizon. Surface enrichment of Hg was observed at most of the sample sites, some paddy fields in particular, resulting in steep concentration gradient down the profiles. The total Hg in all the surface horizons ranged from 459 to 64 ppb with a mean of 197 ppb. Obviously, mercurial application in recent years was a principal factor above all with regard to the establishment of the elevated Hg levels in the upper soil horizon under cultivation. Man-made loading of this element, probably through rai...
TL;DR: In this paper, 15N-labeled nitrogenous compounds such as nitrate, nitrite, hydroxylamine, ammonium, glutamine, glutamic acid, aspartic acid, γ-aminobutyric acid, alanine, glycine and leucine were fed with sunflower leaf discs under light and dark conditions.
Abstract: Sunflower leaf discs were fed with several 15N-labeled nitrogenous compounds such as nitrate, nitrite, hydroxylamine, ammonium, glutamine, glutamic acid, aspartic acid, γ-aminobutyric acid, alanine, glycine and leucine under light and dark conditions. The incorporation of UN into amino acids extracted from the leaf discs was studied. 15N from the inorganic compounds was most actively incorporated into the amido-group of glutamine, the 15N content of which was considerably higher in the dark than that in the light. This result suggests that inorganic nitrogen is incorporated into amino acids after being reduced to ammonium. The application of 15N-labeled amino acids brought about a characteristic UN distribution pattern in each case. The incorporation of 15N into serine decreased remarkably in the dark except for the application of glycine, indicating that the introduction of the aminogroup into serino strictly depends upon tight. Based on the present experiment, a speculative scheme. of nitrogen ...
TL;DR: The effects of carbon dioxide, oxygen, and light on nitrogen fixation in Japan clover (Kummerowia striata S) were examined by the acetylene-reduction method as mentioned in this paper.
Abstract: The effects of carbon dioxide, oxygen, and light on nitrogen fixation in Japan clover (Kummerowia striata S) were examined by the acetylene-reduction method Oxygen was essential for nitrogen fixation in this plant, and the supplementation of carbon dioxide or exposure to light during this time did not alter the rate of nitrogen fixation Japan clover did not show nitrogen fixation under anaerobic conditions, but the fixation activity appeared when CO2 and light were simultaneously supplied to the system The evolution of oxygen by photosynthesis could be a cause of enhancing the nitrogen fixation activity Diurnal variation of nitrogen fixation in Japan clover was also investigated The nitrogen fixation fluctuated in accord with the light intensity of the solar radiation
TL;DR: In this article, the movement of ammonium due to diffusion in paddy soils in Taiwan was investigated in the laboratory, where the authors found that ammonium movement in flooded paddy soil was inversely proportional to the concentration ammonium in the soil solution.
Abstract: The movement of ammonium due to diffusion in paddy soils in Taiwan was investigated in the laboratory. The movement of ammonium in flooded soils was inversely proportional to the concentration of ammonium in the soil solution, which was a function of the quantity of ammonium present, the content of solid matter in a unit volume of soil (bulk density), and the adsorptive property of soil. Although there was a considerable variation in the value of both the ammonium adsorption and bulk density of soils, the adsorptive property was more variable. Therefore, the adsorptive property seemed to be the most influencial factor on the movement of ammonium in flooded soils, where the property had a close relation to the cationexchange capacity. The bulk density of flooded soils in the field could be reproduced in glass tubes under percolating condition in the laboratory. The values of bulk density determined on paddy soils after harvesting or on air-dry soils were considerably different from those in the fl...
TL;DR: In this article, the authors investigated the clay mineralogy of Hijiori and Numazawa Ando soils with special reference to the occurrence and weathering of hornblende and biotite in the parent materials.
Abstract: The clay mineralogy of Hijiori and Numazawa Ando soils was investigated with special reference to the occurrence and weathering of hornblende and biotite in the parent materials The profiles of both soils underlain by pumice beds were developed from tephras of different ages The ages of the Hijiori and Numazawa pumice beds were approximately 10,000 and 5,000 years old, respectively The rock types of all the parent materials belonged to dacite and the existence of relatively large amounts of quartz was noted in almost all of the bulk soil samples The primary mineral compositions were characterized by large amounts of hornblende in the heavy fractions and small amounts of biotite and bipyramidal quartz in the light fractions Though all the soil samples had similar primary mineral compositions, they were divided into two groups on the basis of their clay mineralogical compositions The clay fractions were characterized by the presence of relatively large amounts of opallne silica and vermiculit
TL;DR: In this paper, the population dynamics of the microorganisms responsible for the Mn-deposition were studied from the point of population dynamics, and an aspect of growth habit of Mn-oxidizing microorganisms and also possible existence of two types of the Mnoxidising microorganisms with different growth habit were inferred; one is living free from soil particles in the medium rich in water-soluble organic nutrients and the other grows on the soil particles on the medium p...
Abstract: Certain differences among 4 plots with different fertilizer treatments at Cent. Agric. Exp. Sta. fn Konosu City, Saitama Prefecture, were studied from the point of population dynamics of the microorganisms responsible for the Mn-deposition. The tiny Mn-deposits were detected with benzidine solution and observed under microscope. The number of the tiny Mn-deposits in the plough layer before flooding was decreased in the following order; plot applied with green manure≥plot applied with no fertilizer≥plot applied with inorganic fertilizers≫plot applied with manure. The almost same order in the abundance of the tiny Mn-deposits was found in a model system for the paddy field. An aspect of growth habit of the Mn-oxidizing microorganisms and also possible existence of two types of the Mn-oxidizing microorganisms with different growth habit were inferred; one is living free from soil particles in the medium rich in water-soluble organic nutrients and the other grows on the soil particles in the medium p...
TL;DR: In this article, the Akagawa River was measured seasonally at five sampling stations in the Akaga River which is highly polluted by strongly acid mine water discharged from the abandoned Matsuo sulfur and iron-sulfide mine area.
Abstract: Number of acidophilic iron-oxidizing bacteria, soluble iron, pH, and water temperature were measured seasonally at five sampling stations in the Akagawa River which is highly polluted by strongly acid mine water discharged from the abandoned Matsuo sulfur and iron-sulfide mine area. Other environmental variables of the river water were also determined (titratable acidity. dissolved oxygen, electrical conductivity, sulfate, aluminum, ammonia and nitrate-nitrogen, and phosphate). Distinct seasonal variations in the number of iron-oxidizing bacteria and ferric iron concentration were observed of the river water during the flow and were correlated with seasonal change in water temperature. Hydrogen ion concentration, dissolved oxygen, nutrients for microorganisms, such as, nitrogen and phosphate in the water of the main stream were judged to be not limited to iron oxidation or bacterial growth. Thus, water temperature was found to be a major environmental factor influencing on the activity of iron ox...
TL;DR: In this article, the C/N ratios and the percentage of carbon and nitrogen of each fraction in total fraction in the soil were calculated and the results varied with each soil profile and horizon.
Abstract: In surface horizons (4 samples) and buried humic horizons (14 samples) derived from volcanic ash, the contents of total, fulvic acid. humic acid and humin carbon and nitrogen were determined. The C/N ratios and the percentage of carbon and nitrogen of each fraction in total carbon and nitrogen were calculated. These values varied with each soil profile and horizon. In the surface horizons and the buried humic horizons with age younger than 3,000 yrs. B.P., C/N ratios of soil samples, fulvic acid, and humic acid were low, and those of humin were distributed over a wide range. The C/N ratios increased in the order of fulvic acid, humic acid, humin among these soil samples. Among soil samples which have been buried from 3,000 to 28,000 yrs. B.P., the more were the total carbon contents of soil and also the fulvic acid, humic acid and humin carbon contents, the greater was the tendency of the C/N ratios to rise. The C/N ratios increased in the order of fulvic acid, humin, humic acid among these soil ...