Investigations on the water economy of volcanic ash soils

To elucidate the influence of climate and vegetation upon the vertical distribution of soil moisture and its seasonal change is one of the fundamental problems in the studies on water economy of volcanic ash soils, that cover the larger parts of Japan, and have characteristic soil-water system.¹⁾ Few data are now available in this field, despite the fact that management of volcanic ash soils is practically one of the most urgent problems in Japan.     

Aluminum concentrations in sclerotia from a buried humic horizon of volcanic ash soils in Mt. Myoko,Central Japan

The morphology and chemical composition of fungal sclerotium-like grains collected from the buried humic horizon of volcanic ash soil in Mt. Myoko were examined using a scanning electron microscope (SEM), energy dispersion xray micro-analyzer (EDX), and electron probe micro-analyzer (EPMA). A high C content, low level of Si and high concentration of Al characterized the grains considered to correspond to the sclerotia of Cenoccocum graniforme. The ²⁷Al MAS NMR spectrum of the sclerotia showed the existence of 6- and 4-coordinated Al. X-ray diffraction analyses supported the presence of amorphous Al (ex. Al-humus complex) in the sclerotia.     

Properties and classification of volcanic ash soils around Lake Kuwanuma on the eastern footslope of Mt. Funagata in Miyagi prefecture,northeastern Japan

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.     

Infiltration characteristics of volcanic sloping soils on Mt. Elgon,Eastern Uganda

Water infiltration is an important hydrological process that influences runoff and soil loss patterns in mountain ecosystems. In this paper, we present results on spatial variation in infiltration in croplands on the volcanic soils of Mt. Elgon, in Eastern Uganda. Twelve experimental sites with slope gradients ranging from 12 to 32% were established. Infiltration tests were carried out with a double ring infiltrometer and three measurements were taken at the upper, middle and lower sections of each experimental site to assess the local variability of infiltration. In addition soil information was collected on each experimental site. The soil infiltration data were then evaluated to fit to four commonly used water infiltration models: (1) Philip (1957), (2) Green–Ampt (1911), (3) Horton (1940) and (4) Kostiakov (1932). The twelve experimental sites cover two cropping systems: annual (6 sites) and perennial (6 sites) crops. Based on the results, we examine the spatial variability of infiltration, the relationship of infiltration to landscape position, and the influence of soil composition on infiltration rates on the slopes. The factors affecting spatial variability of soil infiltration were analysed using correlation and regression techniques. Steady state infiltration rates generally increased with the slope gradient and were crop type independent (P < 0.05). The performance of the four applied water infiltration models was generally good with mean R² values ranging from 0.79 to 0.87, although all the models tended to over-predict the steady state infiltration rates at most sites. Overall, the Philip's and Kostiakov gave better results than the Horton and Green–Ampt models in reproducing the infiltration process on Mt. Elgon.     

Weathering and allophane neoformation in soils developed on volcanic ash in the Azores

On Faial and Pico islands (Azores), we studied two profiles on basaltic pyroclasts that contain buried horizons, and we focussed on petrography, micropedology and mineralogy. Emphasis was given to weathering of the lapilli and ashes, and the neoformation of allophane. A combination of optical studies, in situ chemical analyses, X‐ray diffraction and infrared spectroscopy of clay fractions revealed that allophane is present both in the micromass of the groundmass, in alteromorphs after lapilli or pumice, and in clay coatings. Whereas most studies describe allophane as a colloidal fraction formed by the congruent and total dissolution of the ashes, this study shows evidence for the formation of allophane alteromorphs, due to leaching of Si and cations, with preservation of the original shapes of the tephra. The allophane alteromorphs often display optical characteristics that resemble those of palagonite. Increasing alteration is observed through three steps: (i) hydration of the glass associated with strong cation and Si leaching, (ii) allophane hypocoatings, and (iii) allophane alteromorphs with development of intragrain bridges. The chemical signature of the alteromorphs varies from a pure alumino‐silicate at one extreme to an Fe(Ti) enriched alumino‐silicate at the other. Between those two extremes, the colour grades from yellow to dark orange, with microzonations. An Al‐rich allophane composition is associated with gibbsite in the EUR6‐Pico profile, whereas at the base of the EUR5‐Faial profile, Si‐rich allophane is associated with halloysite. Some variations of the palaeo‐environment are also suggested by strong iron segregation observed with various secondary phases (ferrihydrite, haematite, iddingsite).     

Bacterial 16S rDNA sequences in immature volcanic ash soil on volcanoes Mt. Sakurajima and Mt. Fugen in Japan determined by PCR amplification

Volcanogenous soils are widely distributed in Japan. Andosols, a group of volcanogenous soil, are known to show several physicochemical characteristics such as high porosity, presence of allophane, and high content of organic carbon (FitzPatrick 1980). The formation of Andosols is a very rapid process resulting from the large surface area of the volcanic ash-derived parent materials.     

Influence of applied p on the cation exchange capacity of volcanic ash soils

Abstract

The CEC of volcanic ash derived soils in Guatemala was measured following equilibration with 1.5 and 6.0 me P/100 g soil supplied through KH₂PO₄ solutions. An increase in CEC resulted due to P reaction and the increase was substantial after removal of soluble Al from P reacted soils. The average ratios of increase in CEC to P retained were 0.49 and 1.63 in the former and later, respectively. P apparently neutralized positive charges on the surface of amorphous component and those internally in the soil particles resulting in a net increase in negative charge (CEC).     

Clay mineralogy of some volcanic ash soils in which cristobalite predominates

The clay mineralogical composition of soils on volcanic ashes from Mashū and Kamuinupuri-dake volcanoes, Hokkaido, which are rich in cristobalite, was determined using petrological, X-ray diffraction, differential thermal, and selective dissolution and differential infrared spectroscopic methods.

The cristobalite occurred in abundance in every size of fraction from coarse sand to clay and every soli from approximately 1,700 to 8,400 years old, and was concluded to be of igneous origin. The major clay minerals were allophanelike constituents and allophane with some layer silicates as the minor clay mineral, being similar to those of andesitic ash soils and different from those of volcanic ash soils containing abundant quartz. The quartz of volcanic ashes was presumed to bederived from the groundmass-equivalent portion of the ashes which had been formed from magma at a low temperature.     

Porosity and soil water properties of Caribbean volcanic ash soils

Abstract. Volcanic ash soils are generally recognized as soils with excellent and stable physical properties. Here we characterized the porosity and water properties of volcanic ash Andosols and Nitisols from Guadeloupe in contrasting banana systems: (1) perennial crop without mechanization, (2) mechanized and regularly replanted crop. Desiccation from 1 kPa to 1550 kPa moisture tension leads to significant shrinkage in the Andosol, representing a 50% reduction of the void space. The clayey Nitisol exhibited limited shrinkage. Soil clods from the mechanized plots had a significantly smaller macroporosity than that from perennial plots. The soil hydraulic conductivity was also drastically reduced in the compacted layers of the mechanized plots. However, Nitisols appeared to be less affected than Andosols. Laboratory compression tests showed that both soils were susceptible to compaction at soil moisture close to field capacity. The shrinkage properties of the Andosol were due to microaggregation of non-crystalline components upon drying. The relative stability of the macroporosity in the Nitisol was probably related to the presence of stable microaggregates made of halloysite and iron oxide. Two major processes promote soil structure degradation in the Andosol under mechanized banana cropping, surface desiccation and soil compaction. They are both induced by repeated tillage after clearing.     

A climosequence of soils on late quaternary volcanic ash in highland Papua New Guinea

Some chemical, physical and mineralogical properties of three soils developed in volcanic ash at altitudes of 1040 m, 1720 m, and 2350 m in Papua New Guinea's Enga Province are presented. Silt-fraction mineralogy and total chemical analyses show that fresh ash occurs in the upper approximately 30 cm of profile at each site. This fresh ash is probably only a few thousand years old and overlies an older weathered ash (Tomba Tephra;more than 50000 years old). At the lowest site the majority of the primary minerals (predominantly amphiboles, volcanic glass and felspar, and some pyroxenes) have been decomposed by weathering to produce a high clay content. With increasing altitude, greater proportions of silt-sized, unweathered and partially altered primary minerals are recognised and molar ratios of calcium, magnesium, sodium and potassium to aluminum increase accordingly. In the clay fractions, allophane with Al/Si ratios of approximately 2.0 is dominant at the highest site, whereas with decreasing altitude lower proportions of allophane occur, Al/Si ratios decline and halloysite becomes dominant. Gibbsite is found in all three profiles     

Impact of land use changes on the hydrological properties of volcanic ash soils in South Ecuador

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.     

Evaluation of p as a limiting macronutrient in volcanic ash soils of guatemala

Abstract

P status of soils derived from volcanic ash in Guatemala was investigated. Growth chamber and greenhouse studies were conducted with H‐3 hybrid corn (Zea mays). All plants exhibited P deficiency symptoms and yielded less dry matter when they were grown on soils that received only lime at a rate equivalent to 2,240 and 4,480 kg/ha. The P content of plants was low and correlated with P deficiency symptoms. Application of P (336 and 672 kg/ha) under constant liming corrected the P deficiencies and increased dry matter. In comparative studies, plants grown on a highly fertile, non‐volcanic soil showed vigorous growth and yielded high dry matter. Apparently, P was limiting productivity in volcanic ash soils of Guatemala, and due to low exchangeable Al, addition of only lime did not produce beneficial results. The soils responded to P fertilization and they should be supplied large quantities of this macronutrient.     

Field and chemical Evaluation of volcanic ash deposition in some soils of Malaysia

A study was conducted to determine the extend of volcanic ash deposition and distribution in some soils of Malaysia. A total of 12 soil types of different geology and locations from Peninsular Malaysia and West Sarawak were collected and analysed for their physico‐chemical and dissolution analysis. All soils under study belonged to either the order of Inceptisols, Ultisols or Oxisol. They were acidic and had relatively low CEC and exchangeable bases. The Al saturation percent were higher in the Ultisols as compared to the Oxisols. Field and laboratory investigations, and the dissolution analysis comprising of the binary ratio, ferrihydrite percent and allophane content, suggested that the soils under study were highly weathered and non‐allophanic. The soils of West Sarawak, however, may contain a reasonable deposits of the volcanic ash materials, as shown by the higher pH_NaF values of near 9.4, but other laboratory analysis were still not conclusive of the result.     

Amorphous clay minerals of recent volcanic ash soils in hokkaido (ii)

In the previous study (1), it was shown that the size-fractions finer than 2 μ of the soil samples were abundant in siliceous amorphous materials. These materials are more siliceous in the specimens of the A horizons than in the C and tend to become more siliceous with increase of particle-size. Discrete amorphous silica is present in all the size-fractions finer than 2 μ and its amount is considerably greater in coarser clay fractions. Since the proportions of coarser clay fractions are greater in the whole clay fractions, it is considered that the amorphous silica of the coarser clay fractions play a significant role in determining the properties of all of the amorphous clay minerals contained. Amorphous silica exists not only in the fractions finer than 2 μ, but also in the fractions coarser than 2 μ, even in the fine sand fractions of the A horizons.     

Adsorption of silica in river waters by soils in central Chile

The adsorption of the silica in water by soils was investigated using principal river waters and soils collected in central Chile from about 34° to 41° south latitude. The adsorption of silica in water (y) was linearly proportional to the silica concentration in river waters (x) as shown by the following equation:

y=bx-a

where a and b were constants being subject to the nature of the soils. The silica contentration in river waters appeared to relate closely to the rocks in the catchment area. and was high in rivers from volcanic ash areas. However, the salt concentration had no correlation with the silica concentration, and tended to lower to the southward with an increase in annual precipitation and a decrease in annual mean temperature. Sulphate appreciably lowered the adsorption of silica by soils, although chloride and nitrate had little effect on the adsorption. The a-value, dissolution of silica in pure water, was the largest in paddy and alluvial soils, and both the a- and b-values were less in surface soils .in comparison with those of lower horizons. Soils caused neither adsorption nor dissolution of silica at a certain silica concentration. This silica zero adsorption concentration differed greatly from soil to soil, and the largest value which was observed in the surface soil of an irrigated paddy soil was so large that it could not adsorb silica from any river water in the central Chile. In contrast to this soil, an imogolitic subsoil of an Ando soil exhibited the highest adsorption concentration, i.e. it was possible to adsorb silica from every river water in the central Chile. Humus seemed to protect soil silica from dissolution and at the same time to prevent adsorption of silica by soils. Allophanic colloids were labile in water without humic-material, readily releasing silica into the water.     

Interrelationships between microbial and soil properties in young volcanic ash soils of Nicaragua

The activity and biomass of soil microorganisms were measured in soils from 25 different arable sites in the Pacific region of Nicaragua with the objective of elucidating their interrelationship with soil textural and soil chemical properties. All soils developed from recent volcanic deposits but differ in their particle size distribution. Short-term phosphorus fixation capacity varied widely and was, on average, 11% of added P. In contrast, long-term P fixation capacity varied within a small range of around 55%. Mean basal respiration was 8.6 μg CO₂–C d⁻¹ g⁻¹ soil, average contents of biomass C, biomass P, and ergosterol as an indicator of fungal biomass were 116, 1.95, and 0.34 μg g⁻¹ soil, respectively. They were all, except biomass P, significantly lower in the sandy than in the loamy soils. The mean biomass C-to-soil C ratio was 0.69%, the mean metabolic quotient 95 mg CO₂–C d⁻¹ g⁻¹ biomass C, the mean ergosterol-to-biomass C ratio 0.31% and the mean biomass C-to-P ratio 107. The very low ergosterol-to-biomass C ratio indicates that fungi contribute only a relatively small percentage to the microbial biomass. The biomass C-to-P ratio exceeded considerably the soil C-to-total P ratio. Metabolic quotient qCO₂ and ergosterol-to-biomass C were both negatively correlated with biomass C-to-soil C ratio and clay content, indicating positive correlations between qCO₂ and ergosterol-to-biomass C ratio and between biomass C-to-soil C ratio and clay content. Key problems of soil fertility and soil quality in Nicaragua are low availability of soil organic matter and phosphorus to soil microorganisms, which are magnified by a low percentage of fungi, probably reducing the ability of soil to provide nutrients for plant growth.     

Specific gravity of allophane and volcanic ash soils determined with a pycnometer

The determination of the specific gravity of allophane is an interesting and important problem, but it is no exaggeration to say that we have no satisfactory answer to this question in spite of numerous studies. In this note, the specific gravities of allophane, weathered pumices and volcanic ash soil were determined with a pycnometer, and the values compared with those of the other clay minerals and non-volcanic ash soils.     

Evaluation of gas diffusivity models for no-tilled and tilled volcanic ash soils

Accurate quantification of soil gas diffusion is essential to understand the gas transport mechanism in soils, especially for soil greenhouse gas emissions. To date, the performance of soil gas diffusivity (D_p/D₀, where D_p is the soil gas diffusion coefficient and D₀ is the diffusion coefficient in free air) models has seldom been evaluated for no-tilled and tilled volcanic ash soils. In the present study, six commonly used models were evaluated for volcanic ash soils under two treatments by comparing the predicted and measured soil gas diffusivities at water potentials of pF 1.3–3. The Buckingham-Burdine-Campbell (BBC), soil-water-characteristic-dependent (SWC-dependent), and two-region extended Archie’s Law (2EAL) models showed better performance for both no-tilled and tilled volcanic ash soils, which is likely because porosity and pore size parameters of bimodal soils were taken into consideration in these models. Since the BBC model showed better accuracy than the SWC-dependent and 2EAL models and required fewer, more easily measurable parameters, this study recommends the BBC model for predicting soil gas diffusivity of volcanic ash soil under different tillage managements. In future studies, the BBC model should be further tested at water potentials of pF > 3, and may be improved by including the parameters of pore continuity and saturation.     

Effect of sulfate on nitrate transport in volcanic ash soils sampled from the A and the B horizons

Intensive cultivation of crop fields using agricultural chemicals and fertilizers has led to changes in ecological systems, resulting in a high possibility of environmental pollution by contamination, or occasional reactions not only in the soil but also in the water and the atmosphere. Some substances are known to be very toxic to human beings at low concentrations. For example, nitrosamines are believed to be carcinogenic and mutagenic.     

Studies on the properties of organic matfer in buried humic horizon derived from volcanic ash

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 from the samples with the age about 15,000 years B.P. to 28,000 years B.P. may be the same.