Kazutake Kyuma

Comparison of salt titration and potentiometric titration methods for the determination of Zero Point of Charge (ZPC)

Abstract The salt titration (ST) method was evaluated as a method to determine ZPC in comparison with the potentiometric titration (PT) method for 26 soils with variable charge clays, i.e., Oxisols and Ultisols from Thailand and Andisols from Japan. In addition to the determination of ST-pH0 as the zero point of charge, a calculation procedure (STPT method) was adopted here in order to acquire more information from the titration curve. Furthermore, for the purpose of cross-checking of ZPC determined by the PT method, the ST procedure was successively applied to the samples analyzed by the PT method (PTST method). The soil to solution ratios of 1: 10 to 1: 5 gave almost an identical ST-pH0 value for every soil. The values of both ST-pH0 and PT-ZPC ranged from 4.7 to 6.3 for the Andisols, while for the Oxisols and Ultisols, they were always below 4.2. The difference between the values of ST-pH0 and PT-ZPC was only slight for the Andisols, whereas it was sometimes large (0.4 pH unit) for the Oxisols and Ulti...

Changes in soil fertility and tilth under shifting cultivation. I. General description of soil and effect of burning on the soil characteristics

In response to the world-wide concern on the conservation of forest and soil resources in the tropics, an experiment was conducted in northeast Thailand to study various ecological aspects of shifting cultivation in monsoon tropical Asia. The present study deals with the soil changes during the cropping phase of the experimental shifting cultivation. The experimental site was located on a hilly land at the elevation of 800 m under the tropical savanna climate. The vegetation was a semi-deciduous seasonal forest with about 330 ton/ha of aboveground biomass. The soil is derived from Mesozoic sandstones and shales with a pronounced reddish coloration. Field as well as laboratory characterization revealed that the major soil group in the experimental plots was a Lithic Ustropept, with a few scattered spots of Ultic Haplustalfs and Typic Troporthents. Effect of burning of felled trees on the soil profile was very conspicuous in reburn piles, but generally negligible in other areas. A comparison between the soi...

Factors affecting zero point of charge (zpc) of variable charge soils

The factors which determine or exert an influence on the zero point of charge (ZPC) of soils were examined, using 26 variable charge soils from Thailand and Japan. ZPC was mainly correlated with amorphous A1 for the Japanese volcanic ash soils, and with crystalline Fe oxides for the Thai Oxisols and Ultisols. Besides, significantly high correlations were found between the ZPC and the specific surface area, and phosphate absorption coefficient. Sample soils were categorized into three groups on the basis of the ZPC value, namely, Group 1 with a ZPC value higher than 5.5, Group 2 with a ZPC value ranging from 4.5 to 5.5, and Group 3 with a ZPC value lower than 4.5. Amorphous A1 oxides for Groups 1 and 2 and crystalline Fe oxides for Group 3 were the prominent factors relevant to ZPC. Among other physico-chemical properties, the total carbon content was closely associated with the ZPC variations. No definite sequence of ZPC within a pedon was observed for the volcanic ash soils, reflecting the difference in ...

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.

Measurement of soil respiration in the field: influence of temperature, moisture level, and application of sewage sludge compost and agro-chemicals

Soil respiration data were obtained using a portable infrared gas analyzer by measuring the CO2 concentration in a small chamber placed on the ground. The rate of respiration showed a geometrical mean of 11.4 (mmol- h-1 -m-2) and ranged from almost 0 to about 80 (mmol-h-1-m-2) in the experimental field in the farm of Shimane University (103 plots, 1,081 data). The rate was stimulated strongly by the temperature (R2 = 0.76, Q10 = 2.2, 4°C <, < 40°C), and weakly by the moisture level (partial correlation coefficient: 0.4) and input of organic matter. But the influence or agro-chemicals (standard and 5-fold dose of fenitrothion, chlorothalonil, and paraquat dichloride) was too small to be detected in the field.

Effects of inorganic nitrogen application on the dynamics of the soil solution composition in the root zone of maize

The effect of inorganic nitrogen (N) fertilizer on the ionic composition of the soil solution under maize (Zea mays L.) was studied. A pot experiment was carried out with two treatments combined factorially, with or without N application (Ca(NO3)2; +N and −N treatments, respectively), and with or without plants. Three looped hollow fiber samplers were installed in each pot to sample soil solutions nondestructively from the root zone, seven times during the 50-day growth period. Plants were harvested on the 50th day, and their nutrient contents determined.Effects of N fertilizer on the soil solutions were observed by the first sampling, 2 days after sowing. The concentrations of Ca and NO3− and electrical conductivity (EC) increased significantly in the +N treatments as direct effects of fertilizer application. In addition, the concentrations of Mg, K, Na and H+ also increased and that of P decreased significantly as indirect effects caused by the re-establishment of chemical equilibria. This suggested the greater supply as well as the greater possibility of leaching loss not only of NO3− but also of Ca, Mg and K. In the treatments with plants, the concentrations of NO3−, Ca, Mg and K decreased with time and pH increased significantly compared with the unplanted soil. The depletion of N in the soil solution roughly agreed with the amount of N taken up by the plant. The depletions of K from the soil solution amounted to less than 10% of the amount of the K taken up, suggesting intensive replenishment of K from exchange sites in the soil. Depletions of Ca and Mg were several times higher than the amounts taken up, indicating that the depletions resulted from the adsorption of the divalent cations by the soil rather than uptake by plants. Because NO3− is hardly absorbed by exchange sites in soil and was the dominant anion in solution, it was concluded that NO3− had a major role in controlling cation concentrations in the soil solution and, consequently, on their availability for uptake by plants as well as their possible leaching loss. ei]H Marschner

Changes in zero point of charge (ZPC), specific surface area (SSA), and cation exchange capacity (CEC) of kaolinite and montmorillonite, and strongly weathered soils caused by Fe and Al coatings

Abstract In order to analyze the effects of Al and Fe coatings on mineral grains, montmorillonite (Mt), kaolinite (Kt), and deferrated strongly weathered soils (T6B and T7B) were artificially coated with 2, 6, 10% of Fe or Al hydroxides. Changes in the values of the zero point of charge (ZPC), specific surface area (SSA), and cation exchange capacity (CEC) were examined for these samples. Furthermore, observations by X-ray diffraction (XRD) and scanning electron microsocpy (SEM) were made. The effect of sesquioxide coatings on the ZPC, SSA, and CEC values was found to be entirely dependent on the material coated and the type of coating material. In the case of Mt, Al coatings caused a decrease in the inter-lamellar spaces and CEC, and a shift of ZPC to a higher pH value, whereas Fe coatings caused no significant change except for the development of variable charges sufficient to induce a ZPC. In the case of Kt and the deferrated soil samples, Fe coatings brought about a shift of the ZPC to a higher pH val...

Influence of pyrite oxidation and soil acidification on some essential nutrient elements

Abstract Influence of soil acidification on some essential nutrient elements was observed experimentally during periodic leaching at 10-day intervals of pyritic soil materials. Pyritic soil in glass columns saturated with distilled water was treated under waterlogged or submerged and drained conditions. Waterlogged was inundated and had overlying water of 2-cm depth above soil surface. Extremely acidic soil conditions, caused mainly by oxidation of pyrite (FeS 2 ), led to other serious problems. Results showed that strong acidification of soils influenced the solubility and availability of some nutrients. The loss of calcium (Ca), magnesium (Mg), zinc (Zn), and copper (Cu) was enhanced by acidification. Intense acid conditions also dissolved manganese (Mn), high amounts of which would lead to toxicity problems in plants and animals. As oxidation progressed, soil acidification increased and depressed availability of phosphorous (P), thereby, leading to the deficiency of this nutrient. Sodium (Na) and Chlorine (Cl) were leached out rapidly in both treatments regardless of soil acidification. The common problems associated with acid soil formation from oxidation of pyrite are fish mortalities and very poor response of the soil to phosphorous fertilization. For idle land or areas abundant in pyritic materials, soil acidification can be avoided by inundation with water to a depth of 2–3 cm, rather than draining and exposure, which lead to the formation of acid sulfate soil. Periodic leaching was found effective in reducing soil acidity although some essential nutrients were also removed. Therefore, fertilization during amendments is found to be of necessity.

Use of a looped hollow fiber sampler as a deyice for nondestructive soil solution sampling from the heterogeneous root zone

Abstract Information on the water and nutrient dynamics in the root zone is essential for appropriate soil management and fertilizer application, since the root zone is the area where soil and plant interact. It is especially important to study the dynamics of the soil solution composition and concentration because many previous studies on the mineral nutrition of plants grown in soil suggested that plant roots take up nutrients from the soil solution. It is, therefore, necessary to develop an appropriate apparatus for the collection of soil solutions from the heterogeneous root zone.

TRACE ELEMENTS IN TROPICAL ASIAN PADDY SOILS : I. Total Trace Element Status

Four hundred eighty two samples of paddy soils collected in ten Tropical Asian countries were analyzed for total contents of eleven trace elements, i.e. boron, chromium, cobalt, copper, molybdenum, nickel, rubidium, strontium, vanadium, zinc, and zirconium. Results were presented in histograms, showing the distribution patterns of the data, and tables, showing the statistical summaries of the data by countries. In general, it appeared that among the Tropical Asian paddy soils, the Philippine soils contain high amounts of total cobalt, molybdenum, strontium, vanadium, and zinc but low amounts of total rubidium and zirconium. Burmese soils show high amounts of total boron, chromium, copper, molybdenum, nickel, and zinc. Vietnamese soils are rich in total chromium, molybdenum, and rubidium. Cambodian and both East and West Malaysian soils are generally poor in most of the total trace elements studied. Contents of the total trace elements studied in the soils of Sri Lanka, Bangladesh, India, Indonesia, and Th...