Kan-ichi Sakagami

Role of Soil Organic Matter in Stabilization of Water-Stable Aggregates in Soils under Different Types of Land Use

Abstract Three Andosols (used as grassland, upland field, and paddy field) and two Gray Lowland soils (used as upland field and paddy field) were examined to study the role of organic matter in the stabilization of soil aggregates. It was found that prolonged use of Andosols as grassland or as upland field enabled to maintain a higher level of soil organic carbon than use as paddy field. However, paddy soil exhibited a greater aggregate stability (determined by wet-sieving procedure) than soil under upland field or grassland management. Comparison between two Gray Lowland soils also showed that aggregates in the paddy soil were more stable than in the upland field soil. Among organic constituents examined (such as sodium pyrophosphate (SPP)-extractable organic matter and carbohydrates), only the contents of hot water (HW)-extractable carbohydrates of the soils were significantly correlated with aggregate stability. Paddy soils which showed a greater aggregate stability contained a larger amount of HW -ext...

Seasonal variations in soil microbial biomass content and soil neutral sugar composition in grassland in the Japanese Temperate Zone

Abstract We investigated seasonal variations in the soil microbial biomass N content (MBN) and the soil neutral sugar composition from April 1995 to September 1996 in cattle-grazed pasture in a Japanese Andisol. MBN showed seasonal variation, gradually increasing from April to August, and decreasing rapidly by the end of August when soil moisture content decreased. Soil inorganic-N increased after fertilization and cattle pasturage. Seasonal variations in seven types of neutral sugar-C contents in the soil were observed. However, the trends in seasonal variation for sugars derived from plant materials were different from one another and from those derived from microbial products. Seasonal variation trends in soil neutral sugar-C were similar to that of MBN, with a sharp decrease in midsummer and a subsequent increase in autumn probably due to dence pasture plant growth. Furthermore, galactose-C (Gal), rhamnose-C (Rham) and ribose-C (Rib) that originated mainly from microbes showed positive correlations with MBN, but the other forms of soil neutral sugar-C did not. It was concluded that the composition of the soil organic matter accumulated in grassland varied seasonally, and that these seasonal variations can be investigated by MBN or by soil neutral sugar composition.

Effect of amending materials on growth of radish plant in salinized soil

Abstract The critical Na levels in soil which restricted seed germination and growth of radish, and effect of the amending materials on reducing the salinity hazard were determined by performing petri dish and pot experiments. The plants were grown in amended salinized soil in a phytotron for 21 days. Excess accumulation of Na in cells suppressed seed germination and plant growth. The critical Na level in control soil which restricted germination and growth was 12.5mg Na/g soil. At the same salinity level, amending materials promoted seed germination and plant growth mainly by inhibiting the excess flow of Na into the cell through ion holding mechanism. Among the materials used, the commercial manure of 4 months old held greater amount of Na(3.7mg/g) and thus more efficiently reduced the ion damage. Plants grown under such treatment had the highest dry matter yield (28.Gmg/plant), water content was normal(84%), and the ratio for Na in root to Na in plants shoot was 2.4. As for the case of plant grown in ...

Relationship between soil neutral sugar composition and the amount of labile soil organic matter in Andisol treated with bark compost or leaf litter

Abstract The effect of short-term bark compost (Ba) and leaf litter (Li) applications on the labile soil organic matter (SOM) status was investigated. The SOM status studied in this paper includes soil microbial biomass, soil available N, hot water extractable C (HwC) and N (HwN) and soil neutral sugar-C composition. The soil microbial biomass C (MBC) and N (MBN), soil available N, HwC and HwN increased upon application of Ba and Li. No quantitative relationship was observed between application of organic material and MBC, MBN or soil available N. A positive linear correlation was observed between MBN and HwC but not between MBN and soil available N. Among the various soil neutral sugar C, xylose C (Xyl) content in Ba plots showed a remarkable increase but mannose C (Man) did not differ among Fer (fertilizer), Ba or Li plots. Soil neutral sugar C had a positive linear correlation with soil available N, MBN and HwC. The proportion of MBN : TN is positively correlated with the Xyl/Man ratio. The increase in the proportion of MBN in SOM seems to occur with the increase of SOM derived from plant debris.

Relationship between Neutral Sugars and the Degree of Humification in Andisols

Abstract We investigated the relationship between the amounts of neutral sugar carbon (NSC) and total carbon content (TC) or the degree of humification of soil organic matter (SOM) using 14 Andisols in Japan. The amounts of 7 kinds of NSC, TC content and the degree of humification of humic acids expressed as RF values were determined. Positive linear correlations were observed between the amount of every kind of NSC and TC Especially the amount of mannose carbon which was likely to be adsorbed on the mineral components in soil and is considered to be mainly of microbial origin was highly correlated with TC (r = 0.912**). However the correlation of cellulose-type glucose-C which was assumed to be mainly of plant origin was less significant (r = 0.603*) compared with other kinds of NSC. The proportion of total NSC (TNSC) in TC was negatively correlated with RF values (r=− 0.623*). Furthermore the proportion of TNSC in humic acid carbon was also negatively correlated with RF values (r= −0.891**). In a conclu...

Acid hydrolysis kinetics of soil carbohydrates

k Values (rate constants of hydrolysis) of soil carbohydrates were measured in an acid-hydrolysis procedure. Samples were hydrolyzed with sulfuric acid, and neutral sugars (glucose, galactose, mannose, arabinose + fucose + fructose, xylose and (rhamnose) were determined in the hydrolyzates by HPLC. Average k values of each component sugar and total sugars were calculated from the following first order kinetics model; Y = A[1 − exp(−k·t], where Y is the amount of sugars in the hydrolysate at the time t. k values of purified FAPs (fulvic acid ethanol precipitates) were higher than those of crude FAPs. It is considered that the linkages between carbohydrates and other soil components were broken down during the purification process, and so carbohydrates of purified FAPs were hydrolyzed more easily. k Values of humic acids which were insoluble due to aggregation in acidic solution were lower than those of fulvic acids which were soluble. It was also found that k values of fulvic acids were lower at high salt concentrations. These results suggested that soil carbohydrates occurred in the soil in forms resistant to acid-hydrolysis as a result of some insolubility mechanism, such as salts or complexes with soil components or aggregation.

Determination of component sugars in soil organic matter by HPLC.

Summary Component sugars of soil carbohydrates were determined by high performance liquid chromatography (HPLC). The principle of this method is ion-exchange chromatography of sugar-borate complex anions on a column of strong-base anion exchange resin, combined with a sensitive method for post-column fluorometric detection of reducing sugars with the use of arginine as a detection reagent. Glucose, galactose, mannose, xylose, rhamnose and ribose were separated, but arabinose, fucose and fructose were eluted in the same peak. There were no interferences with other substances. Reproducibility test carried out with the same sample was satisfactory. Quantitative detection limits for individual sugars were approximately 30—60 ng. It took less than one hour to analyse each sample. No pretreatment was required except for the filtration of the substances which precipitated at pH 8. This method is considered to be applicable for the determination of component sugars in the hydrolysates of soil carbohydrates or free monosaccharides in soil. Nature and origin of soil carbohydrates was also discussed. The presence of substantial soil carbohydrate which is a certain type of carbohydrates intrinsic to soil organic matter which is neither on immediate product from plant nor microorganisms was suggested.

Characteristics of buried humic horizons at the Shiiji archeological pits: I. Chemical properties and humus composition of buried horizons

To investigate changes in the nature of soil organic matter with lapse of time after burial, buried humic horizons derived from volcanic ash with an age from the present to 27,200 YBP were studied and the properties of the soil organic matter in each horizon were assessed. The results for the chemical properties and humus composition of the soil samples were as follows. 1) Based on stratigraphical studies (1), the Ashitaka Loam Formation is divided into two groups of alternate layers, Kuroboku soil in the surface part, and the Upper loam below the Kuroboku soil. The total carbon and nitrogen contents were high in the horizons of the Kuroboku soil and low in the Upper loam. The relationship between the total carbon and nitrogen contents had a positive correlation. 2) The humus compositions of the two groups were as follows. (1) Kuroboku soil: This was characterized by large amounts of humic acid extracted with NaOH and small amounts of both humic acid and fulvic acid extracted with Na6P2O7 Compare...

Evaluation of Pg absorption strength of humic acids as a paleoenvironmental indicator in buried paleosols on tephra beds, Japan

Abstract Pg absorption strength of humic acid is the strength of a type of green pigment appearing in the spectral curves of humic acid, which derives from many species of fungi. Previous studies on surface A horizons of Andisols have shown a high positive correlation between the Pg absorption strength and the estimated yield of Sasa , the representative forest floor vegetation of deciduous broad leaf trees. In this study on the buried A horizons of Andisols (paleosols) in Japan, we confirmed the same positive relationship between Pg absorption strength and the yield of Sasa . We evaluate Pg absorption strength of humic acid as a paleoenvironmental indicator, which is an attribute of pedogenetic biological influence preserved in buried paleosols.

Humus accumulation in Holocene paleosols formed in Japanese tephra

Abstract Andisol profiles develop according to the rates of volcanic ash supply and of soil formation. In many parts of Japan, there are tephra-Andisol sequences with buried soils which are rich in humus and clay. The buried soils were formed approximately 5–8 ka ago during the Holocene Climatic Optimum, and since then extensive environmental changes have occurred. The vertical distributions of organic C, the C/N ratio and molecular weathering ratios (silica/alumina, alumina/bases) were examined in Holocene tephra-Andisol sequences in Northern, Central and Southern Japan to trace changes in the strength of pedogenetic weathering and variations in biomass during the Holocene.