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1.
One of the developments in recognition of soil properties and different soils is from morphological to analytical. With an incorporation of analytical data, transitional soils can be systematically named using a key-out order as well as typical soils. Our major objective was to evaluate soils with multiple forming processes such as andosolization, podzolization, etc., using soil analytical data, selecting a small area having different soil names based on soil morphological properties. According to a local soil map, Ando soils, Brown forest soils (Dark) and Wet and Dry podzols soils are adjacently distributed around Lake Kuwanuma on the eastern footslope of Mt. Funagata in Miyagi prefecture, northeastern Japan. We studied the morphological, chemical and mineralogical properties of these soils and classified them according to the recent Comprehensive Soil Classification System of Japan (CSCSJ), United States Department of Agriculture Soil Taxonomy (ST) and the World Reference Base for Soil Resources (WRB). The elevation of Lake Kuwanuma is 780 m above sea level and a plateau is located next to a steep slope on the western side of the lake. Three pedons were sampled from the northern side of Lake Kuwanuma, and 3 additional pedons were sampled from the plateau. The average difference in elevation between these two groups of pedons was 229 m. All 6 pedons were classified as Andosols in CSCSJ, Udands in ST and Andosols in WRB. Thus, andosolization was the dominant soil-forming process throughout the study area. The major modification of Andisols in the study area was caused by forest vegetation. Of the 6 pedons sampled, three were classified as Fulvudands in ST and had the Fulvic prefix qualifier in WRB. Furthermore, weak podzolization was suggested on the basis of soil profile observations. One pedon on the plateau had a Bs horizon, which satisfied the spodic horizon requirements of ST. Thus, weak podzolization, especially on the plateau, was another accessory characteristic in the present study area. The nearby distribution of Podzols soils and Ando soils in the local soil map may be explained by differences in temperature, leaching intensity and other factors. A podzolic subgroup of Andosols/Udands was desired to express the properties of pedons on the plateau in the lower categories of the recent soil classification systems.  相似文献   

2.
Relationships between abiotic oxidation and adsorption of phenolic acids added to soils and soil chemical properties were investigated by using 32 soil samples and ferulic, vanillic, and p-hydroxybenzoic acids. Soil properties studied were as follows: (as adsorption factors) contents of acid oxalate extractable Al (Alo), Fe (Feo), dithionite-citrate-bicarbonate (DCB) extractable Fe (Fed), total carbon and clay, and (as oxidation factors) level of soil oxidative activity (Cr oxidation) determined by the amount of Cr(VI) converted from Cr(III) added to soils. Soil samples were divided into 3 types based on chemical properties: Andosols A (A horizon of Andosols), Andosols B (B horizon of Andosols and light-colored Andosols), and non-Andosols.

The recovery of all phenolic acids (RPA) was negatively correlated with the total carbon and Feo contents in Andosols A and B, respectively, which suggested adsorption onto soil organic matter in Andosols A and onto Feo in Andosols B. It was considered that almost no oxidation of phenolic acids occurred in Andosols A, because a very small amount of Cr(VI) was obtained. The recovery of ferulic acid (RFA) and vanillic acid (RVA), however, was negatively correlated with Cr oxidation in non-Andosols, suggesting that these phenolic acids were oxidized, while almost all of the p-hydroxybenzoic acid was recovered.

These results were also supported by the comparison between RFA and recovery of dissolved organic carbon (RTOC). RFA was very similar to RTOC in Andosols A and B, which indicated that adsorption occurred, whereas RFA was lower than RTOC in the non-Andosols that showed a high level of Cr oxidation, indicating that oxidation took place. Manganese dissolution which occurred when phenolic acids were added to soils was also examined.  相似文献   

3.
Organic carbon stocks and soil erodibility in Canary Islands Andosols   总被引：3，自引：0，他引：3  
Soil organic carbon (SOC) plays a key role in the structural stability of soils and in their resistance against erosion. However, and as far as andic soils are concerned, these mechanisms and processes, as well as the influence of the different types of SOC on aggregate stability, are not fully understood. The targets of this paper are: (i) to determine the content and forms of SOC in Andosols under evergreen forest vegetation [laurel (Laurus) and heather (Erica) forest] and (ii) to find out the role of soil organic matter (SOM) in the aggregate stability and in the resistance of Andosols to water erosion. Soil samples have been collected in 80 sites in a 40 km2 area under udic soil moisture regime. In them, fulvic and humic acids, Walkley–Black SOC, pyrophosphate-extractable SOC, Fe and Al, potassium sulphate extractable SOC, dissolved SOC, acid oxalate-extractable Fe, Al and Si, USLE K-factor and aggregate stability have been determined. The Andosols over volcanic ash are Aluandic Andosols (non-allophanic Andosols), whereas over basaltic lava flows are Silandic Andosols (allophanic Andosols). The surface (0–30 cm) samples analyzed contain 9.5–30 kg C m− 2 being significantly higher in allophanic Andosols (p < 0.5). Organic carbon adsorbed onto the mineral fraction (extractable pyrophosphate, Cp) accounts for 35–55% of the total SOC. All samples show a high stability to slaking and raindrop impact, being the first one highly correlated (r = 0.6) with pyrophosphate extractable C (Cp), Fe (Fep), and Al (Alp) in allophanic Andosols, unlike non-allophanic ones. The stability to raindrop impact correlates with pyrophosphate extractable C (Cp) and Fe (Fep) in both types of soils (r = 0.3–0.6, p < 0.05). These findings suggest that the high stability to both slaking and water-drop impact is due to the occurrence of allophane–Fe–OC complexes, rather than to the total OC, and the active Fe and Al forms, generated by the weathering of volcanic materials, constitute an essential constituent responsible for C sequestration and resistance to degradation in these soils.  相似文献   

4.
Potato common scab induced by Streptomyces scabies is a serious constraint for potato-producing farmers and the incidence of potato scab depends on the soil chemical properties. We examined the chemical characteristics of conducive and suppressive soils to potato common scab with reference to the chemical properties of nonallophanic Andosols, recently incorporated into the classification system of cultivated soils in Japan. Allophanic Andosols with a ratio of pyrophosphate-extractable aluminum (Alp) to oxalate-extractable aluminum (Alo) of less than 0.3–0.4 were “conducive” soils with a high allophane content of more than 3%. On the other hand, nonallophanic Andosols with a Alp/Ala ratio higher than this critical value were “suppressive” soils, and their allophane content was less than 2%. The concentration of water-soluble aluminum (AI) was also a useful index for separating conducive from suppressive soils as well as the Alp/Ala value and allophane content. The suppressive soils showed a much higher concentration of water-soluble Al at pH 4.5 to 5.5 than the conducive soils. The high concentration of water-soluble Al may be responsible for the control of the incidence of potato common scab in Andosols.  相似文献   

5.
Abstract

To clarify the effect of soil type on changes in sugar beet (Beta vulgaris L.) productivity since 1980 in Tokachi District (Hokkaido, Japan), we analyzed yield data from 121 settlements from 1980 to 2002 using maps of parent materials and surface organic matter contents in a geographical information system. The soil types were Brown Lowland soils, Andosols with an alluvial subsoil, Wet Andosols and Andosols. The sugar beet yields were highest in the Andosols and moderate in Andosols with an alluvial subsoil. Yields in Brown Lowland soils in the 1980s were similar to those in Andosols, but decreased below the yields in the Andosols by the 1990s. The yields in Wet Andosols were the lowest in the 1980s, but have been similar to those in Andosols with an alluvial subsoil since 1990. Thus, productivity appears to have varied over time in Brown Lowland soils and Wet Andosols. The correlation coefficients between yields and cumulative daily mean temperature from late April to mid-July since 1990 were highest in the Andosols (r = 0.67), lowest in the Brown Lowland soils (r = 0.50) and intermediate in the other soil types (r = 0.54–0.60). However, the magnitude of the correlation between the yield and the cumulative precipitation since 1990 was lowest in the Andosols (r = –0.22), highest in the Brown Lowland soils (r = –0.58) and intermediate in the other soil types (r = –0.44 to –0.45). These results suggest that the present soil water environment in the Andosols is superior to that in the other soil types.  相似文献   

6.
Abstract. The effect of land use on the water retention capacity of Umbric Andosols in south Ecuador was studied. The objective was to acquire a better insight into the hydrological processes of the ecosystem and the role of the soil, in order to assess the impact of changing soil properties due to land use change on the hydrology of the high Andes region. Field data on the water retention capacity at wilting point of Umbric Andosols were collected for both cultivated field conditions and original bush vegetation. The pH in water and in NaF, texture, organic matter content and dry bulk density were measured to show which physicochemical soil characteristics are responsible for the water retention of the Umbric Andosols and for the irreversible loss in water retention due to air drying. Organic matter content appears to be very important and certainly more important than allophane clay content. Water retention of the organic litter layer was calculated to be 16 mm, this would be lost when vegetation was cleared and the land cultivated.  相似文献   

7.
ABSTRACT

Following the Fukushima Daiichi Nuclear Power Plant accident of 2011, the potential for radiocesium transfer from contaminated soils, such as Andosols, to agricultural crops became a significant concern. Andosols account for up to 70％ of paddy soils in the northern and northwest areas of Tochigi Prefecture, where the radiocesium concentration is 1000 Bq kg?1 or greater in the soil of some fields. The present study was carried out in order to determine the phytoavailability of radiocesium in Andosols by comparing it with that of gray lowland soils in the first 3 years following the accident. The transfer factor (TF) tended to be higher in Andosols than in gray lowland soils, leading to higher radiocesium concentrations in brown rice grown in Andosols. The exchangeable potassium (Ex-K2O) in Andosols was highly and negatively correlated with TF, followed by clay. The Ex-K2O value was positively correlated with the clay/total carbon (T-C) value, suggesting that a high T–C ratio could weaken K2O adsorption on clay mineral sites; hence, the low clay/T-C values can partially explain the relatively large TF values of Andosols. Samples with Ex-K2O contents less than 200 mg kg?1 and with low clay/T-C values showed striking decreases in TF values from 2011 to 2012. However, the decrease from 2012 to 2013 was quite small; radiocesium in these samples was potentially available for rice uptake for a long time, likely due to the reversible adsorption and fixation characteristics of allophane. Most gray lowland soil samples showed very low TF values over the 3 years of the study, except for those with TF values greater than 0.1 due to low Ex-K2O and clay contents; the geometric mean (GM) value of TF was below 0.01 in 2012. The extraction of exchangeable radiocesium (Ex-Cs) with a 1 mol L?1 ammonium acetate solution may not be an appropriate method for explaining the variability in radiocesium TF in Andosols. This is because the Ex-Cs value was significantly correlated with Ex-K2O in Andosols, but not in gray lowland soils, indicating that Ex-K2O explained this variability in relation to Ex-Cs.  相似文献   

8.
World Reference Base for Soil Resources (WRB) was published in 1998 and has begun to be used all over the world. We examined the definitions of andic and vitric horizons and qualifiers (lower-level units) of Andosols in the WRB by using the Tohoku University World Andosol Database (TUWAD) and proposed several revisions. Among 5 items of the definition for the andic horizon, we considered that the requirements of clay and volcanic glass contents should be deleted due to the difficulty in their accurate determination with the progression of soil weathering. In relation to this revision, correction of vitric horizon was also proposed. Although two major types of andic horizons, silandic and aluandic, are specified in the andic horizon definition, the aluandic type is not included in the qualifiers. Because aluandic volcanic ash soils have unique properties and are extensively distributed, the aluandic qualifier should be included in the lower level units of Andosols. Soil texture is used for the definition of arenic, luvic and vatic qualifiers. Therefore, these qualifiers should be modified or deleted. Both melanic and fulvic qualifiers are required to obtain the Munsell color value (moist) and chroma of 2 or less. To distinguish fulvic Andosols from melanic Andosols, the Munsell color and melanic index requirements for a fulvic horizon should be modified. Since Andosols with buried non-Andosols occur in a significantly large area, the thaptic qualifier should be used.  相似文献   

9.
Mechanism of reduction of exchangeable aluminum in acid Andosols treated with gypsum was studied by using cation exchange resin methods to determine the amount of polymerized aluminum. Two types of acid Andosols were used as test soils: Kitakami light colored Andosol (fine, mixed, mesic, Andic Dystrochrept) and Kawatabi thick high humic Andosol (medial, mesic mixed Alic Pachic Melanudand). Polymerization of aluminum in the soil solution of both Kitakami and Kawatabi Andosols treated with gypsum was suggested based on an analysis using cation exchange resin methods, whereas that in monomer aluminum solution was not detected. Accumulation of polymerized aluminum in both Kitakami and Kawatabi Andosols was determined by using cation exchange resin, and the amounts of polymer aluminum trapped by the resin and the ratio of polymer aluminum to monomer aluminum were increased with the incubation time. The values of CEC which decreased in the Kitakami Andosol after gypsum treatment were almost equivalent to the amounts of cation exchange sites occupied by polymer aluminum ions which were calculated based on the decrease of the values of Y l. We conclude that the mechanism of reduction of exchangeable aluminum in strongly acid Andosols treated with gypsum is as follows: firstly, exchangeable aluminum adsorbed on the cation exchange sites of soils may be released into the soil solution due to the increase in the ion strength caused by gypsum application, and then monomer aluminum in soil solution may be polymerized in the presence of soil colloidal materials. Consequently, the polymer aluminum formed in the soil solution may be selectively and irreversibly fixed on the cation exchange sites of 2 : 1 clay minerals.  相似文献   

10.
The distribution of zinc, manganese, copper, cobalt, and nickel in Andosols was investigated. Sixty nine soil samples were collected from different horizons of an Andosols profile in Miyakonojo Basin in south Kyushu, Japan, The total contents of heavy metals were determined by digestion and four extraction solutions, 1 M NH4Ac (ammonium acetate) pH 4.5, 0.1 M HCl, 0.01 M EDTA (ethylenediaminetetraacetic acid) pH 6.5, and 0.005 M DTPA (diethylenetri-aminepentaacetic acid) pH 7.3 were used to determine the contents of available Zn, Mn, Cu, Co, and Ni in Andosols in relation to the organic carbon content. The results of the extraction analysis showed that by the use of 0.1 M H Cl high value of extracted heavy metals in the upper layers of the humus horizons were obtained while EDTA extraction yielded a large amount of the above mentioned metals in the high humus horizons. The extractable heavy metals contents were high and these metals closely related to the organic carbon content mostly in the humus horizons in the profile. Where, biocycling process may play an important role in the concentration of heavy metals. Based on the study, it was found that the total content of Zn increased towards the C horizons or pumice layers in the soil profile. Such a trend was also found in the case of the Mn content. While the Cu content in the humus horizons was much higher in the upper part of each humus horizon. According to this study the distribution of heavy metals, Cu (organic matter complexes) in the Andosols profile was more stable than that of Zn (organic matter complexes) in soils. It was shown that Zn in the surface humus horizon was enriched but that some amount was leached under buried conditions. The same phenomenon was also observed in the distribution of Mn in the profile. The movement of Co and Ni in the soil profile was limited, as evidenced by the sharp reduction in the concentrations of these two metals in buried soils.

Hence, it is concluded that the distribution of Zn, Mn, Cu, Co, and Ni was considerably higher in the humus horizons of the Andosols profiles.  相似文献   

11.
Soil response to acid and sulphur inputs is influenced largely by the soil's physico‐chemical properties. We studied the effects of such depositions in two types of Andosols exposed to volcanogenic emission (Masaya, Nicaragua), namely Eutric Andosols rich in allophanic constituents, and Vitric Andosols rich in volcanic glass. Small mineral reserves and large contents of secondary short‐range ordered minerals indicate a more advanced weathering of the Eutric than the Vitric Andosols. Strong correlations between soil specific surface and oxalate‐extractable Al, Si and Fe contents highlight the predominant contribution of short‐range ordered minerals to surface area. Both types of Andosols showed a decrease in pH upon acid input. Sulphur deposition increased the soil's S content to 5470 mg S kg?1. However, the acid neutralizing capacity of the soil solid phase (ANCs) was not significantly affected by the acid and S inputs. Non‐exchangeable (mineral reserve) and exchangeable cations and total contents of sulphur and phosphorus dictate most of the ANCs variation. In the Vitric Andosols, mineral reserves contributed up to 97% to these four additive pools, whereas the exchangeable cations accounted for 1–4%. In the Eutric Andosols, the contribution of mineral reserves was less (71–92%), but the exchangeable cation content was greater (1–20%), whereas the contribution of sulphur and phosphorus was significant at 1–15% and 2–7%, respectively. The main process involved in H+ consumption is mineral weathering in Vitric Andosols and ion exchange in Eutric Andosols.  相似文献   

12.
Chemical and optical characteristics of soil humus have been analyzed as “memory” components of the Pleistocene volcanic paleosols in Mexico. We have studied the A1 horizons of buried Andosols of the Nevado de Toluca series and of the modern Andosols formed under different bioclimatic conditions. Data on the organic matter of buried paleosols suggest that Andosols of the Nevado de Toluca series were formed in humid forest ecosystems. Optical characteristics of the humic acids and data on the molecular-mass distribution of the humus make it possible to assume that these soils were formed under pine forests rather than under fir forests.  相似文献   

13.
Abstract

Allophanic Andosols are widely used as a major material in commercial nursery media for fruit vegetables in Japan because of their remarkable physical properties, such as a high water-holding capacity. In the present study, our objectives were: (1) to examine the effect of phosphogypsum (PG) on the chemical properties of Andosols, (2) to investigate the effect of PG on the growth and Ca uptake of melon seedlings. The effect of PG on chemical properties of Andosols was studied using five Andosols with different inorganic and organic colloidal components. The change in soil pH (H2O) was dependent on the soil samples; an increase was observed in the case of Kawatabi 3Bw soil; a sharp decrease in Kawatabi A2 soil; and almost no change or a slight decrease in Kameoka A1, A2 and Bw soils. The water-soluble Ca content was examined as an index of Ca availability in Andosols treated with PG. The increment in water-soluble Ca by PG application was depressed by allophane. The effect of PG application to the nursery media prepared from Andosols on growth and Ca uptake of melon (Cucumis melo L.) was examined in 2002. Three different varieties, Amusu, Earl's and Midorishima, were used in this experiment. The pH value of nursery media was stable at 6.4 ± 0.1 regardless of PG application rate. In contrast, electrical conductivity was clearly increased by PG application, and was reached at 1.2 dS m?1 in 4.0 g L?1 application. The application of PG increased water soluble Ca of nursery media from 1.7 to 5.2 cmolc L?1. Both top and root growth of melon seedlings were enhanced regardless of varieties, dry matter weights were maximized at 4 g L?1 PG application. The Ca uptake of melon seedlings was promoted by PG application in all the varieties. It was suggested that the relative root growth rate of melon seedlings was closely related to the Ca uptake of melon seedlings.  相似文献   

14.
We have investigated the speciation and distribution of iron (Fe) and aluminium (Al) between minerals and organic species in A and B horizons of two Aluandic Andosols with X‐ray diffraction, thermal analyses, visible diffuse reflectance and Fourier transform infrared (FTIR) spectroscopies, together with selective and total chemical extractions. The two Aluandic Andosols of the Nilgiri Highlands (south India) have formed at the expense of intensively weathered lateritic formations of the Eocene. Data revealed that Al and Fe were predominantly stored in end‐weathering products of laterites, mainly as gibbsite and Fe (hydr)oxides in B horizons of the Aluandic Andosols. These secondary minerals are gradually replaced by organo‐metallic complexes in the topsoil A horizons exhibiting andic properties. We then indicate that formation of the organo‐metallic complexes results from weathering of the dominant crystalline Al‐ and Fe‐(hydr)oxides mediated by the organic ligands and complexation of the polyvalent metals following the accumulation of organic matter. Such weathering and complexation mechanisms are therefore similar to those recently ascribed to deferralitization and the formation of freely drained Umbric Podzols (Humus‐Podzols) in the upper Amazon Basin. In the present case, large supplies of both Al‐ and Fe‐bearing minerals provide large metal:carbon ratios that prevent the mobility of the organo‐metallic complexes and induce the formation of Aluandic Andosols rather than Podzols.  相似文献   

15.
Surface and buried Andosols and buried Luvisols of the Nevado de Toluca Late Quaternary tephra-paleosol sequence (Central Mexico) were studied to show whether these soils present an evolutionary sequence and to determine the pedogenic mechanisms and environmental factors involved in the evolutionary process. Micromorphological observations and mineralogical composition of fine sand and clay fractions were used to detect type and succession of soil-forming process. Some of the buried Andosols, defined as “intergrade” Andosols, have a predominantly blocky structure, humus-depleted areas, redoximorphic features and thin clay coatings in Ah horizons. Clay fractions of buried Andosols contain halloysite besides amorphous components, whereas in modern Andosols, allophane is dominant. Luvisols have micro-areas with granular structure and abundant phytoliths in the groundmass of Bt horizons assumed to be the relict Andosol features. Luvisol clay fractions are dominated by halloysite and kaolinite. Primary minerals show micromorphological weathering features in all studied soils being stronger in Luvisols; however, even in Luvisols, sand fractions consist mostly of unstable volcanic silicates. We hypothesise that the studied profiles form an evolutionary sequence: Andosols–“intergrade” Andosols–Luvisols; the soil transformation is supposed to be linked to progressive crystallisation of 1:1 clay minerals. Comparing the Nevado de Toluca paleosol properties with the existing data on volcanic soil climo- and chronesequences and assessing the regional paleopedological and lacustrine records of Quaternary paleoclimates, we concluded that wet/dry climatic oscillations took place during the formation of the studied paleosols. Rapid crystallisation of 1:1 minerals occurred during dry phases, which speeded up the Andosol to Luvisol transformation and made it independent from the primary mineral weathering status. The Andosol to Luvisol transformation accelerated by climatic fluctuations is thought to be a common soil evolutionary pathway in the subtropical and tropical regions of recent volcanism, which suffered contrasting precipitation oscillations in the Quaternary.  相似文献   

16.
The presence of soils with andic properties on German territory has been suspected for decades and there are numerous reports of sites where they may potentially occur. Andic properties, however, are not adequately represented by the German soil‐classification system. The German taxonomic category “Lockerbraunerde” has not been revised or reconciled with international taxonomic categories since the year 1957, when it was initially proposed. With this review, we show that there are true Andosols of both the silandic (allophane‐containing) and the aluandic (Al‐Humus‐dominated) type in Germany and that their properties differ substantially from other soils which merely exhibit low bulk density. By (1) comparing soil carbon storage between some German Andosols, Chernozems, and nonandic Cambisols with particularly low bulk density and (2) elucidation of the differential pedogenetic pathways leading to Andosol formation, we further demonstrate that Andosols are important objects of study in research issues of contemporary interest. We propose that appropriate measures be taken to lay the foundations for the protection and conservation of these soils, because they are valuable as archives of natural history and provide opportunities to study unique soil processes.  相似文献   

17.
A number of soils are described in the literature as having andic and spodic soil properties, but have developed in nonvolcanic and nonallophanic materials and lack typical Podzol eluvial and illuvial horizons. They cover a wide range of parent materials and different types of climate. They have always been regarded as restricted to small areas. They were assigned to Andisols/Andosols, Podzols/Spodosols, or andic Inceptisols in the WRB and Soil Taxonomy and sometimes also named Cryptopodzols or Lockerbraunerden. Recent soil surveys in Bhutan, E Himalayas, show these soils are widespread at altitudes between 2200–3500 m asl and are spanning several bioclimatic zones. The aim of this study is the detailed characterization of specific properties and processes of formation by physical and chemical analyses, NMR spectroscopy, column experiments, SEM, XRD, and 14C dating in one of these soils in E central Bhutan. The results indicate advanced soil development with high amounts of oxidic Fe and Al compounds, low bulk densities (partly <0.5 g cm–3), P retention >85%, and a dominance of Al‐hydroxy‐interlayered phyllosilicates. Scanning electron microscopy of sand fractions indicate microaggregates highly resistant to dispersion. Column experiments show podzolization with mobilization and translocation of DOM, Fe, and Al. Nuclear‐magnetic resonance spectroscopy and 14C ages of 16,000 BP indicate stabilization of DOM. Applying classification criteria, these soils appear to have andic and spodic features, but are neither Andosols nor Podzols senso strictu. Especially the role of Fe seems to be underestimated with regard to the specific soil‐forming processes. Because of their widespread occurrence and distinct properties, we suggest either a simplification of the criteria for existing soil types or a clearly defined separation of volcanic and nonvolcanic/nonallophanic Andosols.  相似文献   

18.
Andosols and the soil components (allophanes, humic acids, and goethite) had been autoclaved to destroy the nuclease activity of soil microflora. DNA adsorption by allophanes and Andosols was decreased by increasing the amount of α-casein added to the allophanes and to soils up to casein concentration of 5 mg ml?1. DNA adsorption by humic acids was significantly increased by increasing the amount of α-casein up to 1.0 mg ml?1, whereas the addition of 20 mg α-casein ml?1 completely blocked DNA adsorption. These results can explain why the addition of excess skim milk is operationally needed for effective DNA extraction from Andosols. The amount of DNA adsorbed by Andosols treated with dephosphorylated α-casein was significantly higher than that of not treated Andosols (p?相似文献   

19.
Quantity and quality of soil organic matter (SOM) affect physical, chemical, and biological soil properties, and are pivotal to productive and healthy grasslands. Thus, we analyzed the distribution of soil aggregates and assessed quality, quantity, and distribution of SOM in two unimproved and improved (two organic and two conventional) grasslands in subarctic Iceland, in Haplic and Histic Andosols. We also evaluated principal physicochemical and biological soil properties, which influence soil aggregation and SOM dynamics. Macroaggregates (>250 µm) in topsoils were most prominent in unimproved (62–77%) and organically (58–69%) managed sites, whereas 20–250 µm aggregates were the most prominent in conventionally managed sites (51–53%). Macroaggregate stability in topsoils, measured as mean weight diameter, was approximately twice as high in organically managed (12–20 mm) compared with the conventionally managed (5–8 mm) sites, possibly due to higher organic inputs (e.g., manure, compost, and cattle urine). In unimproved grasslands and one organic site, macroaggregates contributed between 40% and 70% of soil organic carbon (SOC) and nitrogen to bulk soil, whereas in high SOM concentration sites free particulate organic matter contributed up to 70% of the SOC and nitrogen to bulk soil. Aggregate hierarchy in Haplic Andosols was confirmed by different stabilizing mechanisms of micro- and macroaggregates, however, somewhat diminished by oxides (pyrophosphate-, oxalate-, and dithionite-extractable Fe, Al, and Mn) acting as binding agents for macroaggregates. In Histic Andosols, no aggregate hierarchy was observed. The higher macroaggregate stability in organic farming practice compared with conventional farming is of interest due to the importance of macroaggregates in protecting SOM and soils from erosion, which is a prerequisite for soil functions in grasslands that are envisaged for food production in the future.  相似文献   

20.
Andosols are characterized by an abundance of black humic acids (HAs) belonging to Type A with a high content of aromatic carbon (C) in particular condensed aromatic C. Black HAs are also observed in other soils, such as Chernozems and the subsoil of paddy field, and extracted after washing with an acid or using chelating agent such as sodium pyrophosphate (Na4P2O7). However, contribution of condensed aromatic structures to those soil HAs are unknown. To obtain the information about C skeletal structures of black HAs in soils other than Andosols, HAs were obtained from 2 Chinese Chernozem samples, 2 subsoil samples from Japanese paddy fields (Fulvisols), and a Rendzina-like soil (Cambisols) as well as an Andosol sample (reference) by successive extraction with 0.1 M NaOH (HAs1) and 0.1 M Na4P2O7 (HAs2), and 13C nuclear magnetic resonance and X-ray diffraction 11-band profile analyses were applied. In the black HAs2 from the non-Andosol samples, the proportion of C present as aromatic C, size of C layer planes, and relative C layer plane content ranged from 52 to 59%, 0.48 to 1.92 nm (mean size, 0.76–0.91 nm), and 58 to 100 AU (arbitrary unit) mg?1, respectively, with a positive correlation between total C layer plane content and the degree of humification. Those ranges were similar to the distribution ranges of Andosols HAs1 reported by our previous study.  相似文献   

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