Composition of iron-manganese concretions from some New Zealand soils

A selection of iron-manganese concretions from five reference soil profiles and a buried loess deposit in New Zealand have been studied. Concretions appear to have developed by the precipitation of amorphous iron and manganese oxides among soil particles. X-ray fluorescence analysis shows that the concentrations of Fe, Mn, Co and Ba in the concretions are generally higher, and those of K, Ca, Si, and Al are generally lower, than in the soil materials surrounding the concretions, whereas Ti, Zn, S, and P show little variation. Other approximate analyses indicate that Cu, Ni, Mo, V, and Pb tend to be concentrated in concretions but for Ga, Zr, Sr, Li, and Rb there was no discernible trend. Electron probe microanalyses of some concretions show that Co and Ba are concentrated in Mn-rich phases rather than Fe-rich phases.Comparison with published results for concretions (Mn nodules) from the ocean floor and the floor of Lake Ontario indicates that, on average, marine concretions have higher Mn, and lower Si and Al concentrations than soil concretions, and that marine concretions have lower Fe concentrations than either Ontario or soil concretions.     

Release of potassium from some benchmark soils of India

Release of potassium from 15 surface samples of benchmark Alluvial, Red and Black soils of India to 0.01 M solutions of BaCl₂, CaCl₂, NH₄Cl and NaCl was studied in soils either untreated or pretreated with 5 × 10⁻³ M KCl. In the untreated soils, the efficacy of the extractants declined in the sequence: BaCl₂ > NH₄Cl > CaCl₂ > NaCl. Cumulative K-release was greatest from Black soils, followed by Red and Alluvial soils. From soils pretreated with 5 * 10⁻³ M KCl, more K was released than retained, and more 'native' K was released than that from untreated soils. Increase in the release of 'native' K decreased in the sequence: Red > Alluvial > Black soils. The amounts of surface and internal K, desorption rate constants and parabolic diffusion constants were calculated from K release to the various electrolytes.     

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.     

b-Fabric of some benchmark Vertisols of India in relation to their mineralogy

At present precise information on the b-fabric of Vertisols is inadequate for gaining a comprehensive knowledge about such soils formed in alluvium of basic igneous and metamorphic rocks and spread in varying agro-climatic zones of peninsular India. The aim of the present study, on five benchmark Vertisol series (Sarol, Aroli, Nimone, Bellary and Kovilpatti), was to assess the possible reasons for differences in the b-fabric of the subsoils despite their common shrink-swell properties, as evidenced by the presence of sphenoids and/or slickensides, and similar clay contents and amounts of fine clay smectite. In Sarol and Aroli soils from the sub-humid region, the b-fabric is porostriated, whereas in Nimone and Kovilpatti soils of the semi-arid and Bellary soils of the arid regions the fabric is either mosaic-speckled or granostriated, indicating weak plasma separation, a result of restricted swelling of clays. The related distribution pattern of the s-matrix in all these soils was open porphyric. Recent literature has suggested that weak plasma separation is an effect of dissolution and crystallization of calcite. However, generally low concentrations of soluble calcium (c. 1 mmol dm^?3) in soil solutions of Vertisols in arid and semi-arid agroclimates suggest that the presence of calcite does not guarantee the presence of sufficient soluble calcium to impair swelling of clays by contracting the diffuse double layer. Weak plasma separation in Bellary and Kovilpatti soils compared with Sarol and Aroli soils is explained in terms of a decrease in the internal surface area of fine smectite, as evident from a very high degree of chloritization in smectite interlayers, and smaller proportions of coarse smectite. In Nimone soils the weak plasma separation is primarily due only to a decreased internal surface area of fine smectite.     

磷的吸附和表面电荷特征及其与华南地区某些土壤矿物的关系

The phosphate adsorption and surface charge characteristics of the tropical and subtropical soils derived from different parent materials in China were determined, and their relations to soil mineralogy were analysed. The results showed that all soil phosphate adsorption curves were well fitted by Freundlich equation and Langmuir equation. The maximum buffering capacity of P ranged from 66 to 9 880 mg kg^-1, with an increasing order of purple soil, skeletal soil, red soil, lateritic red soil, yellow soil and latosol; and the highest value was 149 times the lowest value, which indicated great differences among these soils in phosphate adsorption and supplying characteristics. The pH₀ (zero point of charge) values obtained by salt titration-potential titration varied from 3.03 to 5.49, and the highest value was found in the latosol derived from basalt whereas the lowest value was found in the purple soil. The correlation analysis indicated that the main minerals responsible for phosphate adsorption in the soils were gibbsite, amorphous iron oxide and kaolinite; and the pH₀ was mainly controlled by kaolinite, gibbsite and oxides.     

Exchange properties and mineralogy of some soils derived from lavas of lower old red sandstone (devonian) age. II. mineralogy

The mineralogy of some soils developed on tills derived from basalt and andesite of Lower Old Red Sandstone age has been investigated by X-ray diffraction and optical and scanning electron microscopy. All particle-size fractions as well as some unweathered Lower Old Red Sandstone lavas are rich in layer silicate minerals. The lavas contain abundant saponite of hydrothermal or late-stage deuteric origin. This mineral occurs in rõck fragments which are found in the coarse sand and as aggregated grains in the fine sand and silt and is responsible for the high cation-exchange capacity of these fractions. As well as saponite, the clays contain kaolinite, illite and a variety of dioctahedral interstratified minerals. Scanning electron microscope observations show that plagioclase felspar grains in the fine sand fraction commonly bear regularly shaped etch pits which seem to indicate weathering by solution. The exchangeable calcium and magnesium in the soils derive mainly from decomposition of plagioclase felspar and saponite, respectively, the increasing magnesium content down the profile reflecting the higher content of saponite in the lower horizons. In all probability the exchangeable potassium which is concentrated in the clay fraction is preferentially sorbed at exchange sites on particle edges and is not associated with any particular clay mineral. Clay-mineral aggregates in lava-derived soils may be common, but they can originate in three different ways, viz,, pedogenic cementation, weathering of primary minerals, and inheritance from parent rock.     

Iron oxide mineralogy of some soils of two river terrace sequences in Spain

The iron oxides of soils of two river terrace sequences in Spain which show an increasing degree of redness with age were studied. Clay fractions contained only small amounts of oxalate-extractable Fe. Goethite and hematite, the only crystalline Fe-oxides identified, were determined quantitatively by X-ray diffraction (XRD) after concentrating the Fe-oxides by boiling in $\text{5N}$ NaOH and subtracting the step-counted diffractogram of the deferrated clay from that of the non-deferrated clay, obtaining thus a “pure” Fe-oxide diffractogram. EDTA extracted hematite preferentially to goethite as is seen by loss of red colour and by XRD. A good correlation was found between the content of hematite in the fine earth and a redness rating based on Munsell notations.In the Guadalquivir River sequence, Fe_d and Fe_d/Fe_t increased with age. The amount of both goethite and hematite formed from silicate-Fe increased with soil age but hematite increased more than goethite, possibly due to the xeric soil environment. Also, goethite increased in crystallinity as indicated by a decrease in XRD line broadening and Fe_o/Fe_d ratios. No such trends were found in the Esla River sequence, possibly because the initial alluvium was already highly weathered as shown by high Fe_d/Fe_t values (0.8) irrespective of terrace level.Al substitution in goethite calculated from XRD increased with soil age, reflecting the increasing acidity of the soils. Al substitution in hematite was markedly lower.     

Mathematical models to study the kinetics of potassium release from swell-shrink soils of Central India in relation to their mineralogy

Employing four mathematical models (first-order, parabolic-diffusion, Elovich and zero-order), kinetics of potassium desorption from eight soils with and without cropping were studied to evaluate their ability in explaining K release from soils. The decline in the soil test K in cropped soils over original soils was drastic in easily desorbable forms compared to that of strongly held forms like 3 M H₂SO₄ K. Results showed that parabolic diffusion as well as first-order kinetic equation explained the K release data well for both original and K depleted (cropped) soils. Elovich and zero-order equations were not suitable to describe the kinetic data. However, zero-order equation explained K release data better in case of K-depleted soils as compared to original soils. Soils with higher initial K contents registered higher release rate constants. Over the entire period of cropping the range of release rate (b) decreased from 1.26 to 1.53 × 10^?2 to values ranging from 1.12 to 1.30 × 10^?2 h^?1. In contrast, the first-order equation, parabolic diffusion showed higher b values for cropped soils as they represent the diffusion gradient. Mica and its biotite content in both silt and clay fractions showed significant correlation (r) with b values. Similarly with the rate of K release, clay content of soils maintained significant r whereas the silt content did not.     

An appraisal of the problems in classifying saline-sodic soils of the indo-gangetic plain in NW India

Most of the salt-affected soils of the Indo-Gangetic plain in NW India do not find suitable places in the 1970 U.S. system of soil classification. According to the current class definitions, soils with high salts, ESP, pH, chromas and yellower hues key out as Typic or Aquic Calciorthids, Camborthids and Haplustalfs which does not spell out their saline-sodic nature. For land-use recommendations, the authors believe it will be useful to set these soils apart at some high categoric level in the system.It is proposed that the structural requirements for the natric horizon be modified to include horizons with high ESP (? 40) but having simple blocky structure with or without tongues of eluvial material. New subgroups, viz. Natric, within the orders of Inceptisols, Alfisols and Aridisols is suggested for the high sodium-saturated soils lacking natric horizons. For similar practical considerations, the high concentrations of salts in soils when associated with high ESP pose problems in leaching and consequently new subgroups, viz. Salic and Salic Natric, within the orders of Aridisols and Alfisols are suggested.The modifications proposed not only place more emphasis on the saline-sodic nature of these soils but also result in better groupings for practical land use.     

Studies of some soils in the NW Himalayas and the highlands of India

A reconnaissance soil survey of the NW Himalayan mountains and highlands in the Lahul valley (Himachal Pradesh) was undertaken and five soil profiles from different regions and supporting different vegetation, representing both virgin and cultivated lands, were studied, described and classified in two major soil series, viz. Krozing and Shainsha. The clay fraction of these soils consists of illite and chlorite with minor amounts of kaolinite and traces of swelling chlorite and/or montmorillonite. The removal of amorphous material by a dithionite citrate buffer has been found to be imperative.According to the current definitions, these frigid like high mountain soils having an epipedon on limit with mollic qualify for Dystric Eutrochrepts, which does not depict the reality. Therefore, they have been logically classified, by defining new subgroups of Cryic, Mollic and Cryollic within Eutrochrepts, as Dystric Cryic Eutrochrepts (Shainsha series) and Dystric Cryollic Eutrochrepts (Krozing series). The proposed classification is supported by their geographic situation between Eutrochrepts and/or Hapludolls (in lower valleys) and Cryochrepts and/or Haploborolls (on higher hills).     

Integrated assessment of diversification of rice-wheat cropping system in Indo-Gangetic plain

Diversification of rice-wheat cropping system may improve the productivity and sustainability of agricultural production in the Indo-Gangetic plane region (IGPR), but the choice of alternative sequences to be used requires integrated assessment of various crop sequences. A long-term field experiment was initiated during 2000–01 on sandy loam soil at Banaras Hindu University, Varanasi, India to assess 10 rice-based cropping sequences – rice-wheat, rice-chickpea, rice-wheat-green gram, rice-wheat-Sesbania (green manure), rice-mustard-green gram, rice-lentil-cowpea (fodder), rice-pea, rice-lentil + mustard (3:1)-cowpea (fodder), rice-maize (cob) + vegetable pea (1:1)-cowpea (fodder) and rice-potato-green gram in randomized block design with four replications. The data contained in this paper are for the year 2002–03 and 2003–04. Substitution of rice-wheat with 300% intensity cropping sequences particularly with rice-potato-green gram resulted in maximum production cost but gave the highest system productivity, net return, benefit:cost ratio, production efficiency, profitability and energy productivity. Inclusion of summer grain/fodder legume or Sesbania for green manuring improved the content of soil organic matter. The soil P status was positively affected in all the sequences and particularly those with summer crops. Decline in soil available K in all the sequences indicated inadequacy of present recommended rate of fertilizer K to all the component crops in different sequences.     

Mercury intrusion porosimetry of some New Zealand soils in relation to clay mineralogy and texture

Pore size distributions in the 10/10⁴ nm e.c.d. range in aggregates from three New Zealand soils with largely monomineralic clay fractions, were determined by mercury porosimetry after oven drying and also after critical point drying following methanol and then CO² exchange from a range of water contents. A soil containing halloysite showed considerable porosity in the fine pores (10–30 nm) regardless of the method of drying. A smectitic soil showed virtually no porosity in the 10²–10⁴ nm range when oven dry. A soil containing allophane was dominated by large pores (> 10³ nm). The change from a fine (clayey) to a coarser (clay loam) texture within the profile of one soil was reflected in an increase in large pores.     

The mineralogy and potassium supplying power of some loessial and related soils of New Zealand

Sixteen Pallic (Aqualfs, Ustalfs, Aquepts, Ochrepts) and related soils collected from the North and South Islands of New Zealand were studied to determine if variations in nonexchangeable K supply could be explained by mineralogical composition. A strong relationship was found which indicates that mica is weathering to vermiculite. Proportions of vermiculite and kandite are generally higher in the North Island than in the South Island. Dominance of either micas or vermiculite or kandite is determined by the stage of weathering and/or the nature of parent materials. Soils that supplied more nonexchangeable K (K_nex) to ryegrass plants contained more mica in the clay fraction than soils that supplied less K_nex. The results confirmed that use of a soil test that includes a measure of K_nex (i.e. acid-extractable K) may be a vital part of identifying variations in plant available K status of the soils. It is concluded that the K supplying power of the Pallic and related soils is related directly to the amounts of mica present in clay fraction and that good K supplying soils will be transformed to K depleted soils as a result of increased weathering and leaching (pedogenic factors) and K exploitation in intensive farming systems.     

A study of potassium dynamics and mineralogy in soils from subtropical Brazilian lowlands

Purpose  

The dynamics and availability of potassium (K) in soils depend on many factors, including the mineralogy of fractions and the soil geochemical conditions. The objective of this work is to quantify K in distinct lowland soil compartments in the south of Brazil, relating them to particle size fractions and mineralogical constitution.     

我国几种土壤中铁锰结核的元素组成和地球化学特点

The objective of this research was to isolate a dichlorvos （2,2-dichlorovinyl dimethyl phosphate）-degrading strain of Ochrobactrum sp., and determine its effectiveness in remediation of a dichlorvos-contaminated soil. A dichlorvos-degrading bacterium （strain DDV-1） was successfully isolated and identified as an Ochrobactrum sp. based on its 16S rDNA sequence analysis. Strain DDV-1 was able to utilize dichlorvos as a sole carbon source, and the optimal pH and temperature for its cell growth and degradation were 7.0 and 30 ℃, respectively. Also, the growth and degradation of strain DDV-1 showed the same response to dissolved oxygen. In addition, the soil degradation test indicated that in soil spiked with 100 mg L^-1 or 500 mg L^-1 dichlorvos and inoculated with 0.5% or 1.0% （v/v） strain DDV-1, complete degradation of dichlorvos could be achieved in 24 h. The present study showed that strain DDV-1 was a fast dichlorvos-degrading bacterium in soil. However, further research will be needed to clarify the degradation pathway and the properties of the key enzymes involved in its biodegradation.     

Physico-chemical characteristics of the soils from the coastal plain in Shanghai,China

Characterization of the physico-chemical properties of the soils collected from the coastal plain covering a total area of about 1,908 km² in the Changjiang Delta in Shanghai, China, has been conducted in order to investigate the current status of agricultural soils, with special reference to the effect of alluvial deposits on the development and utilization of the soils. The experimental results indicated that the soils of the coastal plain displayed a sandy (loam) texture. The soils from Qingcun and Guangming Towns in the Fengxian District, Shanghai, contained the highest amount of clay, showing the highest capacity to remain fertile. The soils from Xinghuo Town in the Fengxian District contained the highest amount of salts due to the strong mineralization degree from the groundwater and the effect of the marine deposits from the Hangzhou day, which resulted in the highest exchangeable sodium percentage in the soils. The soils from greenhouses (Sunqiao, Huinan, and Qingcun Towns) showed a higher salt content than others, in contrast to the paddy and orchard soils. The analysis of the soil fertility indicated that the soils from Guangming and Qingcun Towns in Fengxian were rich in organic matter, total nitrogen, and total potassium, and were fertile soils. In contrast, though the soil from Xinghuo Town was rich in potassium, it lacked other nutrients. The phosphorus content in the soils was mainly determined by the application of fertilizers, and the total and available phosphorus contents in the greenhouse soils were higher than those in the soils with other land use types.     

Boron adsorption and desorption in some acid soils of West Bengal,India

Laboratory and greenhouse experiments were conducted to determine the influence of soil properties on adsorption and desorption of boron (B) as well as to estimate the degree of reversibility of adsorption reactions. The utility of Freundlich and Langmuir equations for characterizing the plant availability of applied B in soils was established using soybean [Glycine max (L.) Merr.] as a test crop. The adsorption-desorption study revealed that Fe₂O₃ and clay were primarily responsible for retaining added B in all the 25 different soils under investigation. Organic carbon, pH and cation exchange capacity (CEC) positively influenced the adsorption of B while free Fe₂O₃, organic carbon and clay retarded release of B from these soils. The degree of irreversibility (hysteresis) of B adsorption/desorption increased with increase in organic carbon and CEC of these soils. Freundlich isotherm proved more effective in describing B adsorption in soils as compared to Langmuir equation. The split Langmuir isotherm demonstrated that any of the adsorption maxima, calculated from lower, upper or entire isotherm, could be of practical use. Contrary, bonding energy coefficient, calculated either at lower or higher equilibrium concentration failed to show any practical benefit. Regression models as a function of B application rate and adsorption equation parameters to predict B uptake from applied B, demonstrated the utility of Langmuir and Freundlich equation parameters.     

Clay mineralogy and some chemical properties of Ap horizons of Ando soils used for paddy rice in Japan

The clay mineralogy of the Ap horizons of Ando soils in Japanese paddies was determined by a combination of methods and compared with that of Ando soils of uplands. Six of 13 paddy soil samples contained allophane and imogolite and none contained gibbsite, whereas parallel figures were 15 and 7 for 22 upland soil samples. Substantial numbers of diatoms were found in 5 paddy and 1 paddy-converted upland soil samples. The lack of gibbsite was related to the stage of soil formation rather than the paddy condition, whereas the presence of diatoms was related to both. Regarding layer silicates, there was no particular difference between the paddy and upland soil samples but one unidentified mineral with unique morphology and infrared spectrum was found in two paddy soil samples. There was no particular difference in phosphate adsorption between the paddy and upland soil samples.