Anais da Academia Brasileira de Ciências (2006) 78(4): 749-763(Annals of the Brazilian Academy of Sciences)
ISSN 0001-3765
www.scielo.br/aabc

Green-tuff landslide areas are beneficial for rice nutrition in JapanKAZUE TAZAKI
Department of Earth Sciences, Faculty of Science, Kanazawa University
Kakuma, Kanazawa, Ishikawa 920-1192 Japan
Manuscript received on September 29, 2005; accepted for publication on March 13, 2006;
presented by OTHON H. L EONARDOS

ABSTRACTJapanese Islands are covered with weathered volcanic rocks and soils. Terraced rice field are located ingreen-tuff areas which are very fertile but where landslides occur associated to strong earthquakes. The Xray diffraction and X-ray fluorescence analyses of the soils in landslide area identified predominant smectite
and Mg, Al, Si, K, Ti, Mn and Fe are main components. The rice leaf showed that S, Cl, K and Ca play
important roles for nutrients in the area. Drainpipe systems have set up in the green- tuff areas to reduce therisks of landslides. Reddish brown microbial mats inhabited bacteria and diatom in the drainpipe outlets.
The microbial mats are rich in Fe and PO3−
4 . The iron bacteria in the ground water have a high metabolic
rate suggesting that the weathering materials were produced by not only physical and chemical influence but
also by microorganism. Many microorganisms attach to mineral surfaces and show their high impact in thewater mineral chemistry in the landslide area. Bacteria in the green-tuff over landslide area play importantroles for sustainable agriculture including rice nutrition.
Key words: green-tuff, terraced rice field, landslide, microbial materials.

INTRODUCTION

Volcanic rocks are predominant in Japanese Islands. Weathered volcanic rocks cover mostly thesurface of the Japanese Islands. Terraced rice field
are commonly located over volcanic ashes, pumice
and green-tuffs. The alteration of those rocks generates fertile soils. Otherwise, this area is tectonic active and tragic landslide accidents caused by strong
earthquakes (Shoji et al. 1993; Fig. 1) occurred.
Earthquakes (up to 7 a magnitude of 7) occurredin Niigata at the Japan Sea Coast, on 25th October,2004. In this area, green-tuff formation occurs anda famous agricultural district which produces highquality rice is situated. In this mountainous JapaneseCountry, in flat land, rural houses and rice field areoften built under steep slop.
Factors determine food security and food quality come from the natural factors, such as soil quality,
climate stability, and both water quality and quantity, associated with modern agrotechnology. The
green-tuff areas are the most suitable districts forfarming of rice. We have growing problems related
to chemical nutrient oversupply in Japanese farming. It is the time to think about natural rocks andminerals for crops. Our soils were rich, being derived in large part from volcanic rocks that formed
the Japan Alps along tectonic active fault. These
young soils were full of unweathered minerals capable of slowly releasing nutrients over a long period of time as they were broken down. All forms oflife need a complex array of mineral nutrients andE-mail: kazuet@kenroku.kanazawa-u.ac.jp

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KAZUE TAZAKI

Fig. 1 – Earth quakes in tectonic active areas and landslide distribution in JapaneseIsland. Arrows indicate study areas.

where the soils are poor and subsistence agriculture
has been practiced for a long period of time, manyof these nutrients are simply no long in the soils.
Geochemical map of Japan (Geological Surveyof Japan 2004), using river sediments, provides us
with valuable information on agricultural research
conducted with some of the minerals and rocks
locally available in Hokuriku district in Japan(Fig. 4). The maps with its extensive and up-to-datereferences are an excellent starting point for integrated agricultural research and development workin Japan, for soil scientists, geoscientists, and engineers. The concept of agrogeology certainly needs
more recognition and we must do more to fostertrans-disciplinary research and development totackle our environmental problems and address issues of food security. Soil remediation is critical to
the global problem of food security. We must use

An Acad Bras Cienc (2006) 78 (4)the right “ rocks” on the right “ crops”.
Microorganisms in microbial mats can growand survive in the natural environment including
some of the most extreme and adverse environmenton the Earth (Ohta et al. 2003). Recently, in themost of cases microorganisms have been used as indicators for the investigation of environmental conditions (Khristoforova 1999). The precipitation ofminerals by living organisms is widespread phenomenon that is generally referred to as biomineralization. The significance of bacterial biomineralization is emphasized by the fact that microorganisms are the most abundant life form on the surface of the Earth and live in a variety of environments. Diatoms precipitate silicon on their cell
walls, whereas bacteria can accumulate Fe, Mn, Sr,and some other elements in/on to the cell (Beveridge 1999).

751

GREEN-TUFF LANDSLIDE AREAS ARE BENEFICIAL FOR RICEIn this study, I propose new approaches forsoil remediation using microbes in the drainpipe
outlets over the landslide area, not just the use ofchemical fertilizers. Takayanagi in Niigata prefecture is a typical landslide area for microbial study,
where the drainage systems were established to prevent mudslide occurrence. SEM-EDX observations
revealed the diversity of ecosystem, which depends
on the characteristics of water and soils with usefulelements for the right crops.

MATERIALS AND METHODS

The samples of river sediments, soils and rice leaf
around landslide area, and microbial mats of drainpipes were collected from Takayanagi in Niigata
prefecture, Japan. Water drainage system (throughthe pipe) was established in the landslide areas of
Takayanagi and Oh-hirota in Kashiwazaki, Niigata(H. Segawa et al., unpublished data) (Fig. 2). The
numerous drainpipes were set up in the locality
to inhibit mudslide occurrence (Fig. 3A, B). Eachdrainpipe carried groundwater all the time resulting the formation of microbial mats in the outletof the pipes (Fig. 3C). Different colored microbial
mats with ground waters were collected from thosedrainpipe outlets for analysis. The drainpipes, 50 m
in length, were radially set up for drained groundwater off. The microbial mats are light reddish
brown (point 1), reddish brown (point 2), greenish
brown (point 3), and green microbial mats (point 4)
in color, respectively.
The pH, Eh, DO (Dissolved Oxygen), andwater temperature were measured in the field using a HORIBA portable inspection meter. Microbial mats were examined with a polarizing opticaland fluorescence microscope (Nikon OPTIPHOT2 EFD3). The sample stained with 4’, 6-diamidino2-phenylindole (DAPI) is observed through an
episcopic fluorescence microscope. DAPI method
stains the DNA in bacterial cells, and blue fluorescence under ultraviolet light (365 nm) indicates
metabolically active bacteria.
A low-vacuum scanning electron microscope

38 N

Sado Island
Niigata
138 E

Japan Sea

Sampling
pointsOh-hirota,
Kashiwazaki
Takayanagi,
YamanakaLandslide areas at Takayanagi and Kashiwazaki
in Niigata Prefecture.

Fig. 2 – Locality map of landslide areas shows sampling points
at Takayanagi and Kashiwazaki in Niigata prefecture in Japan.

(LV-SEM, JEOL JSM-5200LV) equipped withan energy dispersive X-ray spectrometer (Philips
EDAX PV9800EX) (SEM-EDX) was used to observe the micro morphology of rice leaf, and its
chemical composition. The samples were mounted
on stubs using carbon tape and examined at accelerating voltages of 15– 25 kV. Mineralogical investigations of river sediments and microbial mats were
performed by X-ray powder diffraction (XRD). A
Rigaku Rinto 1200 X-ray diffractometer (CuKαradiation) operating at 40 kV and 30 mA, and ascanning speed of 1– 20 sec. / 0.02 degree, was used.
Chemical composition of the samples was analyzed using the energy-dispersive X-ray fluorescence (ED-XRF) analyzer (JEOL JSX 3201) applying
Rh radiation at 30 kV. The chemical composition of
microbial mats was determined and the quantityof PO3−4 was made using an automatic gas chromatography.
L ANDSLIDE S ITES AND E PICENTERD ISTRIBUTION IN JAPAN

Locality maps of landslide sites and epicenter distribution were shown in Fig. 1, indicating numberof Earth quakes (1968-1972) in tectonic active
areas set a limit to magnitude between 6 and 8.

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KAZUE TAZAKI

Fig. 3 – Outcrop views of landslide areas with terraced rice field at Noto pen insure (A), largely
slide down the hill beside rice fields in Tochio, Niigata Prefecture, by earthquake in 2004 (B),and drainage pipes at landslide area in Takayanagi, Kashiwazaki in Niigata (C). The geologicalcolumn correlated with the outcrop indicating green-tuff formation.

An Acad Bras Cienc (2006) 78 (4)GREEN-TUFF LANDSLIDE AREAS ARE BENEFICIAL FOR RICE

Most earthquakes are located in tectonically active
areas and volcanic activity is a process generally
related to plate tectonics. Most volcanoes are located at plate junctions where magma is produced
as spreading or sinking lithospheric plates interact
with other earth materials. The occurrence of landslides is closely related to the geological conditions.
Depending on the geological features, landslides
are largely classified into 3 categories, i.e. (1) Tertiary system landslide, (2) Fracture zone landslide,and (3) Hydrothermal zone landslides. Tertiary system landslide occurs in Hokuriku district, associated with soft rock prone to rapid weathering, but
the movement tends to be slow (Koide 1955). Tertiary system landslide commonly occurs at Greentuff system of Noto Peninsula in Ishikawa prefecture and Kashiwazaki in Niigata prefecture, JapanSea cost, where extensively form terraced rice fields(Figures 2 and 3).
G EOCHEMICAL MAPS OF H OKURIKU DISTRICT

Geochemical map of Japan was open to the publicwith valuable information on agricultural research
conducted with some of the minerals and rocks locally available in river sediments (Geological Survey of Japan 2004). The maps with its extensive
and up-to-date references are starting point for integrated agricultural research of “ Rocks for Crops” in
Hokuriku district, Japan. Some of elemental maps
are shown in Fig. 4. The MgO, CaO, P2 O5 , MnO,
and Fe2 O3 maps are closely interrelated with sametendency of high concentrations in Noto Peninsula
and landslide areas at Kashiwazaki and Takayanagi
in Niigata prefecture. On the other hand the K2 O
map is quite different from those elemental maps
indicating low concentration of K2 O at landslide areas, suggesting poor in K-minerals.
RESULTSX- RAY D IFFRACTION A NALYSES (XRD) OF S OILSAT R ICE F IELD IN L ANDSLIDE A REA

Six soil samples were collected from rice field inlandslide area in Niigata prefecture, were analyzed

753

by XRD (Fig. 5). Quartz and feldspars are mainminerals with traces of clay minerals in all bulk
samples. In < 2µm clay fraction of the samples
clearly show abundant 0.14 nm clay minerals under non-treatment. The 0.14 nm diffraction peakshifted to 0.17 nm after EG treatment, is consistent
with smectite. A small amount of 0.10 nm (micaclay minerals) and 0.71 nm kaolin minerals were
found in the soils.
The microbial mats were collected from drainpipe system of the landslide areas of Takayanagi
and Oh-hirota in Kashiwazaki, Niigata. Different
colored microbial mats from those drainpipe outlets showed the almost amorphous XRD pattern,whereas relatively strong peak at 0.15 nm shifts
to 0.17 nm after EG treatment was found as smectite at drainpipe 40 m away from outlets (Fig. 5bottom). A small amount of mica clay minerals(0.10 nm) and kaolin minerals (0.7 nm) are associated with abundant smectite. Note that XRD patterns of rice field soils are similar to those of microbial mats (40 m away), in which smectite was
identified.
E NERGY D ISPERSIVE X- RAY F LUORESCENCEA NALYSIS (ED-XRF)

The untreated soil samples from rice field dispersed
on Mylar film were analyzed by ED-XRF showedthat Al2 O3 , SiO2 , and Fe2 O3 , are main components,
associated with traces of MgO, K2 O, CaO, TiO2 ,MnO, and ZnO in silicate rocks (Fig. 6). The EDXRF chemical results are agreed with XRD mineralogical data.
S CANNING E LECTRON M ICROSCOPY E QUIPPEDWITH E NERGY D ISPERSIVE X- RAY A NALYSIS(SEM-EDX) OF R ICE L EAF

The SEM-EDX observation of rice leaf revealed
the microstructure of stoma, spotted surface, andcoating adhesion materials with their chemical compositions (Fig. 7). Surface of rice leaf shows abundant stoma with regularity composed of Al, Si, S,
Cl, K, and Ca. The K content in the adhesion materials is 4 times richer than Ca content. The chemical

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KAZUE TAZAKI

Fig. 4 – Geo-chemical maps of river sediments at Hokuriku district, Japan. River sediments were used for the chemical analyses(Geological Survey of Japan 2004; open to the public).

An Acad Bras Cienc (2006) 78 (4)GREEN-TUFF LANDSLIDE AREAS ARE BENEFICIAL FOR RICE

755

Fig. 5 – X-ray powder diffraction patterns of rice field soils in Niigata
and microbial mats at landslide area in Takayanagi, Niigata, showing bulk
and < 2µm fraction data with no treatment and after E.G. treatment.

composition data suggest us what kind of elements
are essential for growth of rice leaf in the field.
O PTICAL AND F LUORESCENCE M ICROSCOPICO BSERVATIONS OF M ICROBIAL M ATS

Four kinds of microbial mats from drainage pipes
in landslide area were observed under optical andfluorescence microscopy showing various microorganisms inhabit in each different water systems(Fig. 8 upper). The slightly reduced redox statesof the pipe 3 and 4 were confirmed by Eh valuesof 140– 190 mV and dissolved oxygen levels of
2– 3 mg/l at pH 6.4– 6.5. The other ground water inthe pipes 1 and 2 indicated oxidized conditions, suchas Eh 301– 456 mV and DO 3.8– 6.7 mg/l, indicating
the diversity of ecosystem depend on characteristics
of water systems.
The microbial mats were mainly composed ofcolonies of right brown or transparent microbes
associated with filamentous microbes (Fig. 8 bot-

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KAZUE TAZAKI

XRF chemical analyses of soils at rice field in Gotanda, Niigata (Oct. 2004).
Sample MgO Al2 O3 SiO2 K2 O CaO TiO2 MnO Fe2 O3 ZnO wt%
1
1.22
12.52 52.83 6.38 4.10 1.67 0.60
20.67
2
1.25
13.24 51.35 5.99 3.54 1.69 0.40
22.42 0.11
3
1.25
12.84 52.10 6.11 4.10 1.65 0.66
21.15 0.13
4
1.04
11.91 52.74 6.42 3.96 1.68 0.74
21.50
5
1.12
11.93 53.06 6.30 4.66 1.56 0.65
20.73
6
1.08
11.33 54.79 7.49 4.73 1.70 0.46
18.42

Fig. 6 – X-ray fluorescence analyses (XRF) of soils from six rice fields in Niigata, Japan, show similar chemistry.

tom). Optical micrographs showed abundant diatom in pipe 1 whereas iron oxidized bacteria (Leptothrix ochracea) associated with algal filaments, diatoms, and bacteria of coccus and bacillus type inpipe 3. The microbes fluoresced red when exposed
to light of 510– 560 nm wavelengths, indicating thatthe microbes contain chlorophylla. The various microbes were tentatively identified on the basis of
their morphologies (Holt et al. 1994) as filamentous algae (15– 20 nm in width), filamentous algae(10– 100 nm in diameter), Cyanobacteria (20 nm in
width), and bacteria having coccus or bacillus morphology (< 10 nm in width). The size of sphericalcells ranged from < 10 to 100 nm in diameter.
DISCUSSIONG ROUND S ILICATE ROCKS

Silicate minerals and rocks contain most of thenutrients that plants require for growth and deve-

An Acad Bras Cienc (2006) 78 (4)lopment (van Straaten 2002). Ground silicate rocks
have been investigated for their potential to provide these nutrients to plants in various soil environments. The application of ground silicate rocks
to highly weathered, low fertility, acid soils has
been proposed as alternative to conventional fertilization with water-soluble fertilizers in areas where
fertilizers are not available or in organic agriculture (Leonardos et al. 2000, Coroneos et al. 1996).
Electron microscopic observations of primitive clay
precursors on K-feldspar during microcline weathering under extreme leaching conditions have beenreported (Tazaki 1986, Tazaki and Fyfe 1987a, b).
Green-tuff landslide areas are beneficial forrice nutrition revealed in this study. Rice leaf contains high Si (Fig. 7) which is easily dissolved fromsoils (Fig. 6) under the ground water characteristics
in landslide areas (Fig. 8). Urrutia and Beveridge(1993) have reported the mechanism of silicate binding to the bacterial cell wall in Bacillus subtils.

GREEN-TUFF LANDSLIDE AREAS ARE BENEFICIAL FOR RICE

757

Fig. 7 – Scanning electron microphotographs equipped with energy dispersive analyses(SEM-EDX) of rice leaf collected from landslide areas in Niigata. The stoma, surface, andadhesion area analyses indicated slightly different K/Ca ratio between them.

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KAZUE TAZAKI

Fig. 8 – Characteristic ground water at landslide areas in Takayanagi in Niigata (upper left) andmicroorganisms inhabited in the drainage pipes (upper right). Optical micrographs of microorganisms in the microbial mats collected from pipes 1 and 3 (bottom).

Important aspects of landslides are the typeof earth material on the slope, topography, climate,vegetation, water, and time. The most common driving force is the weight of the slope materials, andthe landslides are a result of an abnormal increase

An Acad Bras Cienc (2006) 78 (4)in water pressure in the slope-forming materials (Keller 1992). The green-tuff from volcanic
materials ids easily weathered to produce smectite
clays with ground water at the landslide area which
has both sides of the advantages and disadvantages

GREEN-TUFF LANDSLIDE AREAS ARE BENEFICIAL FOR RICE

of formation of clay minerals. The weathering process of volcanic glass into allophane was determinedby 27 Al and 29 Si solid state NMR (Hiradate andWada 2005).
NATURAL K- MINERALS AND ROCKS

The most commonly used form of K input in agriculture is potassium salt. These naturally occurring
K fertilizers and mainly obtained from sedimentary
potassium (K-salt) deposits providing minerals suchas sylvite (KCl) or complex K-Mg chlorides and sulfates. The main source of K for plants growing undernatural conditions come from the weathering of K
minerals and organic K-sources such as composts
and plant residues. The most important K minerals are K-feldspar, leucite, K-micas such as biotite,
phlogopite, and glauconite, and clays such as illite.
K-rich silicate rocks with relatively fast weatheringcharacteristics are leucite-bearing volcanic materials. Bacterial bio-weathering of K-feldspar and biotite in granite have been reported by Ueshima andTazaki (1998). Mineral surface is control of organiccarbon in black shale (Kennedy et al. 2002).
Mica minerals such as phlogopite and biotite
contain considerable amounts of K2 O (usually> 10%), MgO (5– 22%) and Fe (5– 20%). Most ofthese nutrients are part of the silicate structure, ina form not readily available to plants and animals.
Electron microscopic and X-ray studies prove thatthe roots of rape and ryegrass can transform phlogopite into vermiculite, releasing K and Mg to theplants. Roots and rhizospheres of plants are active
biological weathering agents that transform micas
and release K and other cations (Hinsinger and Jaillard 1993, Hinsinger et al. 1993). Electron microprobe analyses of phlogopite show a narrow rangeof K2 O from 9.3% to 10.4%, and MgO from 23.1 to26.5% (Erickson 1989). In the weathering zone thephlogopite is altered into vermiculite. If there havebeen attempts to extract K and Mg from phlogopite,
for example, through biological means (bioprocessing or through plants like rye grass), is unknown.
In this study the rice field in green-tuff composed of smectite contains Mg (1%), K (6– 7%), Ca759(4– 5%), and relatively high Fe (18– 22%). The traceelement content of this soil is low, with Ti (1.7%)
and Zn concentrations of less than 0.1%. Montmorillonite is the common clay mineral associatedwith most expansive soils and high CEC. With sufficient water, pure montmorillonite may expand up
to 15 times its original volume, but fortunately mostsoils contain limited amounts of the clay, so it isunusual for an expansive soil to swell beyond 25
to 50 percent. However, an increase in volume
greater than 3 percent is considered potentially hazardous (Hart 1974). In this study green-tuff landslide area have been relatively fast weathered to
produce abundant smectite and small amount of
K mica minerals, suggesting potentially hazardous.
There have been attempts to extract K, Mg, andCa from volcanic materials, are followed by smectite formation with high CEC indicating that thechemical and mineralogical composition of thegreen-tuff rocks is favorable for direct applicationin agriculture.
B IOLOGICAL W EATHERING AND B IO - CLAYS

The principal geologic factors affecting surfacewater runoff and sedimentation include rock andsoil type, mineralogy, degree of weathering, andstructural characteristics of the soil and rock. Fine
grained, dense, clay soils and exposed rock types
with few fractures generally allow little water tomove downward and become part of the subsurface flows. Therefore the drainage density (lengthof channel per unit area) is much greater in the
shale areas than in the sandstone areas. The shapeof a drainage basin is greatly affected by the geologic conditions (Keller 1992). The biosphere iscapable of affecting stream flow in several ways.
First, vegetation may decrease runoff by increasing the amount of rainfall intercepted and removedby evaporation. Second, streamside vegetation may
increase the resistance to flow, which slows down
the passage of floodwater. In steep mountain watersheds, many of the pool environments are importantfor vegetations. Soils with high organic content tend
to be relatively cohesive-they reduce surface ero-An Acad Bras Cienc (2006) 78 (4)760

KAZUE TAZAKI

sion and tend to hold water tenaciously-comparedto sandy soils, which have low cohesion, high porosity, and high permeability (Chenu and Tessier 1995).
Interactions of clays with microorganisms andbacterial survival in soil have been reported (Thengand Orchard 1995). The above principles and processes suggest that runoff can be variable dependingon geologic, physiographic, climatic, and biologic
conditions. Such water saturated areas as landslide
can produce good vegetations. Organisms are able
to form many kinds of minerals, such as clay minerals in volcanic ash soils (Tazaki 2005). Microorganisms produced clay minerals have been identified, and minerals of biological origin contributesignificantly to sedimentary deposits (Lowenstam
1981). An interesting example of mineral deposits
were produced by biological processes is not only
phosphates associated with sedimentary marine deposition, but also organic bio-clays in weathered
volcanic materials.
M ICROBIAL S EDIMENTS

Almost all living organisms are generally relevant
to soil sciences and secondly mineral formation. Organic compounds have a major role in the physicalstructure of soils. Various organic molecules areable to adsorb ions to form soils. These methods
may greatly enhance our studies of the role microorganism play in sediment composition (e.g., mineral formation), their contribution to the sedimentary fabric (e.g. microstructure), and their role in
the lithification process (Riding and Awramik 2000).
Kuma et al. (1999) suggested that diatom were able
to uptake organic-Fe (III) from environments. The
banded iron-manganese structures were formed innatural microbial communities (Tazaki 2000). K.
Koiwasaki (unpublished data) reported from a mineralogical study of diatom that can take part in theformation of biominerals associated with Fe, As,
and S. Microorganisms in microbial mats have theirown niche in the geo-aquatic ecosystem. They could
accumulate various kinds of elements like Fe, Si,
S, P, etc. from the landslide areas. In this study,
Leptothrix ochrecea, a kind of iron oxidized bacte-

An Acad Bras Cienc (2006) 78 (4)ria, was found active in the low temperature under
reductive condition. Basing on the results of water quality, soil chemistry, soil mineralogy, microscopic observation of microorganisms, it seem thatthe water characteristics and microbial diversity inlandslide area indicate the water-mineral-life interactions suggesting food nutrient chains for crops.
The water channels and convective flow withinlandslide area has several ramifications. These water channels deliver bulk fluid around, over, and beneath the micro colonies facilitating nutrient delivery and water removal. Thus, diffusion limitationis encountered at the surface of the micro colonies,
not at the surface of the biofilm (Stolz 2000). In thisstudy, the channels in the landslide area may also
are effect of the transport of bacteria to the surface
and the degree of biofilm erosion, sloughing, andterraced rice field.
Bacterial cells can act as a nucleation site for
Fe-minerals. Formation of such bacterial mineralcomposites has been shown to enhance the immobilization of dissolved metals (Tazaki 2005). The
implication is that the Fe-bacterial mineralizationin the volcanic ash soils and water systems both
fosters and augments the solid phase partitioningof metals from solution. The adsorbed silicic acidmay act as nucleation site of silica deposition on
the surface of microbe (Aramaki et al. 2004, Belkova et al. 2004). In volcanic ash soils may havebeen formed from biochemical weathering products of cohesive materials, which subsequently
controlled the formation of clay-organic complex(Tazaki 2005).

CONCLUSION

The green-tuffs from volcanic materials are relatively fast weathered to produce smectite clays withhigh CEC at landslide area which display bothsides of the advantages and disadvantages of formation clay minerals. XRD analyses of the soils
in landslide area identified the predominant clays
as smectite. XRF analyses of the soils at rice fieldrevealed important concentrations of Mg, Al, Si,

GREEN-TUFF LANDSLIDE AREAS ARE BENEFICIAL FOR RICE

K, Ca, Ti, Mn and Fe which are the main components. SEM– EDX of rice leaf showed a variety ofchemical distribution, suggesting that S, Cl, K and
Ca with water play important roles for rice nutrientsin green-tuff landslide area. Reddish brown microbial mats form in the drainpipe outlets at landslide
water and are rich in Fe and PO3−
4 associated withhigh EC.
Iron bacteria in the landslide water system havehigh metabolic rate, therefore minerals are weathered not only by physical and chemical influence
but also by the influence of microorganism. Many
microorganisms attach to mineral surfaces and show
their high impact in the water mineral chemistry in
the landslide area, suggesting bacteria play important roles for sustainable agriculture including ricenutrition.
The main source of K for plants growing under natural conditions comes from not only weathering of K-minerals, but also from organic K-sources
such as bacterial products. The above principles
and processes suggest that runoff can be variable
depending in geologic, climatic and biologic conditions. Such saturated areas can produce good vegetations. Basing on the results of water quality,
soil chemistry, soil mineralogy, microscopic observation of microorganisms, it seems that the water
characteristics and microbial diversity in landslidearea indicate the water-mineral-life interactions
suggesting food nutrient chains for crops.

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RESUMOAs Ilhas Japonesas são cobertas de rochas e solos vulcânicos intemperizados. Terraços de campos de arroz estão comumente localizados em áreas de tufos verdes, as
quais são férteis, mas estão geralmente sujeitas a trágicos
deslizamentos de terra associados a grandes terremotos.
As análises dos solos por difração e fluorescência de raiosX em áreas de deslizamento identificam a predominância
de esmectitas, cujos componentes principais são Mg, Al,
Si, K, Ca, Ti, Mn, e Fe como principais componentes. A
palha de arroz mostrou que S, Cl, K, e Ca têm importantes
papéis para a nutrição dos solos dessa área. Sistemas detubos de deslizamento foram instalados nestas áreas detufos verdes de forma a reduzir os riscos de deslizamentos. Nas saídas dos tubos de descarga se formou uma esteira de algas microbianas marrom avermelhadas habitadas por bactérias e diatomácea. Os materiais microbianos
são ricos em Fe e PO3−
4 . As bactérias das águas subterrâneas são ricas em Fe e têm uma alta taxa metabólica
sugerindo que os materiais intemperizados foram produzidos não somente por influência física e química, mastambém por micro organismos. Muitos dos microorganismos se prendem às superfícies minerais e apresentam
um grande impacto na química mineral da água nas áreas
de deslizamento. As bactérias nas áreas de tufos verdes
desempenham um importante papel na agricultura sustentável incluindo a nutrição do arroz.
Palavras-chave: tufo verde, terraços de campos de arroz,
deslizamento, materiais microbianos.

REFERENCESACKNOWLEDGMENTS

I would like to express my gratitude to the staffs(Shuichi Shiraishi and Naoto Takahashi) of Nissaku
Corporation for their cooperation in this study.
Thanks are due to the students of the Tazaki’s laboratory (Hiromi Segawa, Kazuhiro Sato, and Hiroki
Imanishi) at Kanazawa University for their technical assistance. This study was partially supported
by Grant-in-Aid for Science Research from the
Ministry of Education, Science, and Culture, Japan(Grant-in-Aid for Scientific Research B).

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