bluuebunny/crossref_metadata_2025_split huggingface dataset:
QUALITY CONTROL IN SOIL SURVEY
Authors: BIE S. W. , BECKETT P. H. T. 
Published: July 2006

SummaryThe paper examines 66 Australian soil surveys in a variety of terrains (but not close forest), by several survey procedures, and published at a range of map scales. It relates the Survey Effort (E) of professional staff (in man‐days per km2) to (I) survey procedure, (2) the kind of mapping unit, and (3) the intricacy of the soil pattern mapped. Intricacy (I), the average number of mapped soil boundaries crossed by 1 km of random linear traverse, is related to the total length of mapped boundary (km per km2).When the surveys are grouped according to survey procedure and mapping unit, the survey effort for each group may be described by a regression of the form
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. B could not be shown to differ significantly between groups. D varied in the ratio 0.5: I, according to whether or not surveys used air photograph interpretation, and in the ratio 0.3:0.7:1.o, according to whether they mapped land systems, other compound mapping units, or simple mapping units.Since the choice of survey procedure and mapping unit is usually governed by the intricacy of the soil pattern the effect of these factors can be summarized in a single regression for all 66 surveys:
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There is a significant (P≤ 0.001) log‐log regression between I and map scale.
AGEING OF HYDROLYSED IRON (III) SOLUTIONS1
Authors: HSU PA HO , RAGONE STEPHEN E. 
Published: July 2006

SummaryThree 0.01m Fe(ClO4)3 Solutions of R= 0, 1, and 2, respectively, were studied over a period of 8 months, where R is referred to the HCO3−/Fe3+ mole ratio in preparation. The R= 0 solution was initially light yellow and clear but rapidly changed to a dense cloudy Suspension after a 9‐day induction period. Hydrolysed species rapidly grew from <10 nm to >650 nm. Particles of intermediate size were not observed during the entire period of study. Settleable FeOOH precipi‐tate was first observed in 5 weeks with 23 per cent of its iron noted as precipitate at the end of 5 months. The R= 1 and R= 2 Solutions were reddish‐brown of low turbidity. Rapid hydrolysis and polymerization were observed immediately after preparation. The hydrolysed species gradually grew in size during ageing and no settleable FeOOH precipitate was observed for at least two years. A hypo‐thesis based on Lamb and Jacques's model of Fe3+ hydrolysis is proposed to interpret the reactions taking place in these three Solutions. In the R= 0 solution, the initial number of nuclei for condensation is low, whereas the poten‐tial supply of Fe(OH)3 is abundant. In the R= 1 and R= 2 Solutions the number of nuclei initially formed is high, whereas a limited amount of mono‐meric Fe(OH)3 is available for condensation. The initial number of nuclei relative to the concentration of monomeric species is the key factor that governs the appearance and properties of these Solutions.
ELECTRON‐SPIN RESONANCE OF HUMIC ACIDS FROM CULTIVATED SOILS
Authors: CHESHIRE M. V. , CRANWELL P. A. 
Published: July 2006

SummaryAn examination has been made of the electron‐spin resonance spectra of humic acids from (i) two groups of cultivated soils from the north‐east of Scotland, and the related natural soils from which the cultivated soils are considered to be derived, and (ii) some Rothamsted soils.With the Scottish soils the humic acids from the more acid natural soils (pH <4.6) show e.s.r. spectra with a four‐peak structure (class I), and those of the less acid soils (pH >4.6) almost structureless spectra (class II).The cultivated soils contain humic acids with the same class of spectrum as that of the soils from which they are derived, even though they are now much less acid (PH 5.9 –6.5).Humic acids from Rothamsted soils, sampled recently, were compared with those from the same site sampled 80 years previously. Where the soil has been allowed to revert towards a natural state but still contains free calcium carbonate the pH remained high (7.8–7.9) and the spectrum of the humic acid remains class II. Where the soil contained no free calcium carbonate the pH has fallen from 7.1 to 4.5 on reversion and the spectrum class of the humic acid has changed from II to I.The results support the hypothesis that the class of spectrum of the humic acid depends on the pH at which it is formed.
THE RESIDUA SYSTEM OF CHEMICAL WEATHERING: A MODEL FOR THE CHEMICAL BREAKDOWN OF SILICATE ROCKS AT THE SURFACE OF THE EARTH
Authors: CHESWORTH WARD 
Published: July 2006

SummaryThe residua system of chemical weathering is here defined as the chemical sink towards which the bulk of earth's surface materials (i.e. the silicate rocks) trend during weathering. Chemically the system is defined in terms of four major components, SiO2–Al2O3–Fe2O3–H2O, evidence being derived from relative solubilities of components under earth‐surface conditions; from experiments in which weathering environments have been simulated in the laboratory; and from field studies of rocks and their weathered mantle. The residua system can be used as a framework to construct mineral facies diagrams showing assemblages of the commonest earth‐surface minerals that occur within it: quartz, gibbsite, goethite, kaolinite, halloysite. In a qualitative manner the facies diagrams can then be interpreted in terms of the partial pressure of water (PH4O) and the temperature, T. The usefulness of this approach in systematizing studies of soil genesis is illustrated with reference to the weathering of granite.
THE INFLUENCE OF IRON AND ALUMINIUM HYDROXIDES ON THE SWELLING OF Na‐MONTMORILLONITE AND THE PERMEABILITY OF A Na‐SOIL
Authors: EL RAYAH H. M. E. , ROWELL D. L. 
Published: July 2006

SummaryHydroxy Fe and A1 interlayers reduce the swelling of Na‐montmorillonite in NaCl solutions. A deposit of sesquioxide round an aggregate or orientated flake of clay restricts swelling until the sesquioxide coating is broken by the swelling pressure of the clay. A1 is more effective than Fe.The effect of sesquioxides on the permeability to NaCl solutions of an alkali soil depends on the control of clay swelling in a manner expected from the above results. A sesquioxide coating round a soil aggregate stabilizes the structure until the coating is broken by the swelling pressure of the clay in the aggregate.
PLUMBOGUMMITE MINERALS IN A STRONGLY WEATHERED NEW ZEALAND SOIL
Authors: ADAMS J. A. , HOWARTH D. T. , CAMPBELL A. S. 
Published: July 2006

SummaryPhosphate minerals of the plumbogummite group were tentatively identified in a strongly weathered and leached New Zealand soil formed from granite by comparing changes in inorganic phosphate fractions, after calcination, of a soil sample with those occurring in Christmas Island rock phosphate. This identification was confirmed by X‐ray diffraction. Plumbogurnmite minerals were mainly concentrated in the so‐called residual organic P fraction with a lesser but significant proportion in the residual inorganic P fraction. Phosphate minerals of this group may be quite common in other strongly weathered New Zealand soils.
THE REACTIONS OF SOLUBLE ALUMINIUM WITH MONTMORILLONITE
Authors: BROWN G. , NEWMAN A. C. D. 
Published: July 2006

SummaryThe amount of aluminium sorbed by calcium bentonite from basic aluminium chloride solutions depends on the ratio of OH to A1 in the original solution. Except when OH/A1 = 0, only part of the sorbed A1 is exchanged by dilute solutions of barium or calcium chlorides and the exchange capacity of the clay decreases in proportion to the amount of aluminium retained by the clay. Al‐bentonite appears to contain a mixture of A13+ and a basic cation in which OH/Al is 2.5. Neutralizing Al‐bentonite with calcium acetate of pH 7.2 restores only part of the exchange capacity and some charged interlayer aluminium is thought to remain in the clay at this pH. It seems possible, therefore, that charged interlayer aluminium may be found even in soils with a neutral reaction.
OCHRE FORMATION IN FIELD DRAINS IN PYRITIC SOILS
Authors: TRAFFORD B. D. , BLOOMFIELD C. , KELSO W. I. , PRUDEN G. 
Published: July 2006

SummaryTwo distinct forms of ochre are known to occur in field drains. One form, which is most common in wet peaty areas, is caused by the growth of filamentous iron bacteria. The second form is associated with Thiobacillus ferrooxidans, and occurs where the soil contains pyrite.Contrary to previous reports, liming decreases the rate at which pyrite is oxidized in soil and, by decreasing the amount of iron entering the drains in a given period, should significantly increase the active life of the drainage system. Regular liming is probably preferable to a single large initial dressing.
GAMMA RADIATION FOR MEASURING WATER CONTENTS IN SOIL COLUMNS WITH CHANGING BULK DENSITY
Authors: OLESEN S. E. 
Published: July 2006

SummaryWater profiles in soil columns were measured by the single‐source gamma radiation method. Together with the normal attenuation equation, linear or parabolic equations for the relation between bulk density and volumetric water content were used. To compensate for moderate changes in the bulk density during the experiment both initial and final bulk density and the water content were used in the water profile estimations.For a sandy loam soil, the radiation method without any corrections for bulk density changes resulted in a mean error of the volumetric water content estimation of 0.035 cm3 cm−3, when the water content changed from 0.35 to 0.15 cm3 cm−3. By correction for changing bulk density by means of a linear or a parabolic equation the maximum difference between real and estimated water content was 0.009 and 0.002 cm3 cm−3, respectively. Applying the latter method and a count of 105 the error of a single water content measurement was 0–004 cm3 cm−3.
AN EXAMINATION OF THE FALL‐CONE METHOD FOR THE DETERMINATION OF SOME STRENGTH PROPERTIES OF REMOULDED AGRICULTURAL SOILS
Authors: TOWNER G. D. 
Published: July 2006

SummaryMeasurements of unconfined shear strengths were made over a range of moisture contents on seven remoulded agricultural soils which covered a range of textures, and these were used to calibrate the Swedish fall‐cone device. It was found that the calibration factor, usually regarded as constant in engineering literature, was dependent on soil texture, but constant over a range of moisture contents for a given soil texture.From the assumption that the liquid and plastic limits correspond to two fixed specified strengths, it is shown that one can use the fall‐cone device to determine these limits by making measurements of cone penetrations over a range of moisture contents. It is suggested that a modified plasticity chart, which can be obtained very simply from measurements of cone penetrations made over a restricted range of moisture contents, may be used for characterizing soil behaviour.
ADSORPTION OF THE HERBICIDE 2,4‐D ON GOETHITE
Authors: WATSON J. R. , POSNER A. M. , QUIRK J. P. 
Published: July 2006

SummaryAdsorption, of the herbicide 2,4‐Dichlorophenoxyacetic acid (2,4‐D) on an iron oxide, goethite, was studied in aqueous suspensions as a function of solution pH, ionic strength of the medium, and initial 2,4‐D concentration.The 2,4‐D anion was reversibly adsorbed on positively charged goethite surfaces, maximum adsorption being observed near the pKa of 2,4‐D (2.73) and at low ionic strength. Within certain levels of adsorption (5–22 mg 2,4‐D adsorbed/g goethite) the complex became hydrophobic and floated to the liquid surface. This flotation effect disappeared on further adsorption.It is suggested that adsorbed 2,4‐D anions are orientated with their hydro‐phobic aromatic ends directed towards the solution, the carboxyl groups being weakly bound to positive sites on the oxide surface. At high levels of adsorption, some of the anions are orientated in the opposite direction by π–π interaction, with the first adsorbed layer and the surface reverts to its hydrophilic nature.
SOLUBLE ALUMINIUM AND CALCIUM‐ALUMINIUM EXCHANGE IN RELATION TO THE pH OF DILUTE CALCIUM CHLORIDE SUSPENSIONS OF ACID SOILS
Authors: BACHE B. W. 
Published: July 2006

SummaryMeasurements of pH and A1 concentration were made on 10‐2 M CaCl2, suspensions of a number of acid soils that had been limed to give 3 range of pH values, and exchangeable A1 and Ca+Mg were determined in 1.0 M NH4Cl extracts. The variation of pH with A1 concentration did not support the theory that pH is controlled by the solubility of Al(OH)3. For some of the soils, proton release on hydrolysis of A13+ions in solution accounted for the pH values, and explained quantitatively the variation of pH with the Ca:Al balance of the exchange complex, taking account of the selectivity coefficient for exchange, Kca→A1 Although Kca→A1 was smaller for soils containing more humus, their pH values were also less than those predicted by the hydrolysis of A13+ in solution, indicating that they contained other sources of protons, presumably the carboxyl groups in humus.
MEASUREMENT OF SOIL MOISTURE NEAR THE SURFACE USING A NEUTRON MOISTURE METER
Authors: GRANT D. R. 
Published: July 2006

SummaryCorrection factors for neutron moisture meter measurements near the soil surface have been established from readings at several depths taken before and after the removal of 10 cm of surface soil. In determining the factors it is assumed initially that a uniform soil moisture profile exists. The factors are then applied to the measurements and, from calibration of the neutron meter, the soil moisture profile is established. If large variations with depth are revealed, the initial assumption of uniformity of moisture profile does not apply. A method of determining corrections to the computed factors to allow for the variations in the soil moisture with depth is described. This requires a knowledge of the variation of the correction factors with moisture content and methods of determining this are discussed.
INTRODUCTION OF GRADATIONAL AND PEDOMORPHIC FEATURES IN DESCRIPTIONS OF SOILS
Authors: BOS R. H. G. , SEVINK J. 
Published: July 2006

SummaryA soil profile is considered as the result of the interaction of pedogenic and gradational processes. Distinction is made between monopedomorphic, polypedomorphic, and buried soils. Description of these soils often meets with difficulties due to inadequacies in existing profile description systems. A new system is proposed, based on the differentiation between gradational and pedomorphic features. In this system the concept of pedogenetic horizons (A, B, C, etc.) is deliberately abandoned in favour of the recognition or failure to recognize pedomorphic features at a certain depth and over a certain vertical extent. Some examples serve to elucidate the new system.
STUDIES ON THE MINERALIZATION OF UREA, COATED UREA, AND NITRIFICATION INHIBITOR TREATED UREA IN SOIL
Authors: REDDY R. N. S. , PRASAD RAJENDRA 
Published: July 2006

SummaryA laboratory incubation study was conducted with a sandy clay loam soil (pH 7.8) at New Delhi to study the mineralization of urea, coated urea (sulphur‐coated urea, shellac‐coated urea), and urea treated with nitrification inhibitors (N‐Serve, sulphathiazole) a general purpose microbicide (coal tar), and neem (a non edible oil‐seed) cake. Coated fertilizers mineralized much slower than urea; urea‐N from these materials remaining in soil after z weeks of incubation being two to three times that from untreated urea. However, most N from coated fertilizers was mineralized after 4 weeks. Nitrification inhibitors were quite effective in retarding the nitrification of urea; N‐serve being much more effective than sulphathiazole. Neem cake and coal tar extract were less effective than sulphathiazole in controlling nitrification of urea but they did retard the nitrification of urea for z weeks.
IRON AND ALUMINIUM AS CEMENTING SUBSTANCES OF SOIL AGGREGATES
Authors: GIOVANNINI G. , SEQUI P. 
Published: July 2006

SummaryExtraction of five soils with acetylacetone in benzene does not change their particle‐size distribution, compared with no pre‐treatment or dispersion, but it decreases the water stability of soil aggregates. The decrease is closely related to the extent of the extraction of iron and aluminium by acetylacetone in benzene from soils.The metals extracted by acetylacetone are essentially bound to the organic matter. It is suggested they behave as junctions of a net composed of polymeric chains of soil organic matter. The mesh, which exerts a protective action on soil aggregates, is weakened at the junctions of polymeric chains after the removal of metals so that the stability to the disrupting action of water is decreased.
THE POTASSIUM STATUS OF SIX LOESSIAL SOILS OF CANTERBURY, NEW ZEALAND, IN RELATION TO RAINFALL AND RATE OF LOESS ACCUMULATION
Authors: HAY M. J. M. , WALKER T. W. , ADAMS A. F. R. , CAMPBELL A. S. 
Published: July 2006

SummaryA selection of greywacke‐derived loessial soils in Canterbury, New Zealand, was examined to test the hypothesis that soil K status is a function of soil‐forming factors. Soils were selected such that factors besides loess accumulation and rainfall were relatively constant and the effects of each variable could be isolated. Soil K status was evaluated by plant, chemical, and X‐ray diffraction techniques. With increasing rainfall and decreasing rate of loess accumulation soil K status decreased; there was a concurrent decrease in illite and increase in interstratified mineral content of the clay fraction.
EFFECT OF WATER SUCTIONS ON THE GROWTH IN SOIL OF THE CILIATE COLPODA STEINI, AND THE BACTERIUM AZOTOBACTER CHROOCOCCUM
Authors: DARBYSHIRE J. F. 
Published: July 2006

SummaryPure cultures of the bacterium Azotobacter chroococcum, and mixed cultures of A. chroococcum and the ciliate Colpoda steini, were incubated for 35 days in soil samples, which were either saturated or subjected to a constant suction (either pF 1.5, 2.0, or 2.7). Previous to inoculation, the soil samples had been sterilized by y‐irradiation (5 Mrad) and saturated with a solution of glucose and mineral salts.In the samples maintained at pF 2.7, the Colpoda population decreased after inoculation. In the other samples the ciliate populations increased after inoculation, and the duration of each growth period was related to the degree of suction applied. The longer growth periods were associated with the smaller suctions. Twenty‐eight days after inoculation, saturated soil contained the largest ciliate population.Large numbers of Azotobacter cells were present in all samples, although there was a decline in numbers with time. Azotobacter populations in the samples at pF 2.7 did not increase after inoculation, and smaller Azotobacter populations were often present in the mixed compared with the pure cultures at the same pF value.
HYDROLYSIS REACTIONS IN SODIUM‐MONTMORILLONITE SUSPENSIONS
Authors: LLORCA R. , CRUZ‐ROMERO G. 
Published: July 2006

SummaryExplanation of the hydrolysis of Na‐montmorillonite in NaCl solutions if based on Donnan equilibria, the order of the hydrolysis reaction, and CO2–H2O‐NaCl‐NaOH equilibria. Equations describe quantitatively the extent of hydrolysis as a function of per cent clay in suspension, and initial NaCl concentration. Lack of fit between experimental and calculated Na+ and H • activities is attributed predominantly to lack of equilibrium with atmospheric CO2 in the first stages of the reaction, and thereafter to secondary reactions due to chemical instability of protonized clay, when H+ activity continuously decreases. The presence of CaCO3 in natural clay samples leads to pH values 1 to 2 units higher than those due only to hydrolysis.
FLUORIDE ADSORPTION BY ILLINOIS SOILS
Authors: OMUETI J. A. I. , JONES ROBERT L. 
Published: July 2006

SummaryFourteen surface and 6 subsurface horizons of Illinois soils adsorbed significant amounts of F− with release of OH−. At low concentrations, adsorption was described by both Langmuir and Freundlich isotherms. The calculated Langmuir adsorption capacities were related to pH, clay, organic carbon, and amorphous aluminum contents.Two soils with different gross chemical properties behaved in essentially the same manner, with adsorption maxima occuring between pH 5.5 and 6.5. The similarity between adsorption at different pH values for the soils and those for bauxite, allophane and synthesized ‘soil chlorite’, and the lack of adsorption maxima between pH 5.5 and 6.5 for pure kaolinite and montmorillonite, suggest that F− adsorption in the soils is due primarily to the presence of amorphous aluminum oxyhydroxides which are common weathering products in these soils.
DESORPTION AND ISOTOPIC EXCHANGE RELATIONSHIPS OF PHOSPHATE SORBED BY SOILS AND HYDROUS FERRIC OXIDE GEL
Authors: RYDEN J. C. , SYERS J. K. 
Published: July 2006

SummarySorption of added inorganic phosphate (P) was irreversible in four contrasting soils and hydrous ferric oxide gel during 16 h desorption after 40 h sorption at the same (iso)pH. Irreversibility increased with increasing time of desorption above 30 h. When the amount of P which was chemisorbed during the sorption step was subtracted from the amount desorbed, the latter fell on the isotherm describing the more‐physical, potential‐determining sorption. No pH change occurred during desorption and net negative charge decreased by 1 equivalent per mole P desorbed.These results suggested that only more‐physically sorbed P was desorbed at the iso‐pH. The more‐physically sorbed P was also reversible with respect to changes in the ionic strength and cation species of the desorbing solution. The isotopic exchangeability of the more‐physically sorbed P was at least ten times greater than that of chemisorbed P. With increasing sorption time, both the ease of desorption and exchangeability of sorbed P decreased. Subsequent to desorption, the exchangeability of the remaining sorbed P also decreased. These observations are interpreted in terms of the concurrent changes in the amounts of chemisorbed and more‐physically sorbed P.
THE USE OF MOUNDS OF THE TERMITE MACROTERMES FALCIGER (GERSTÄCKER) AS A SOIL AMENDMENT
Authors: WATSON J. P. 
Published: July 2006

SummaryTwelve termite mounds and adjacent Ah and Ap horizons were sampled at three sites near Salisbury, Rhodesia. The mass of termite mounds occupied by M. falciger at one site was estimated at 620 t/ha, and contained the following amounts of nutrients expressed as percentages of the amounts in mounds and Ap horizon combined: extractable Ca 95%, mineral N 81% extractable K 69%, and available P 69%.Pot experiments using perennial ryegrass gave higher dry matter yields from termite mounds than from the Ap and Ah horizons. Crop production could therefore be increased by mixing termite mounds with the soil.
ORIGINS AND STABILITY OF SOIL POLYSACCHARIDE
Authors: CHESHIRE M. V. 
Published: July 2006

SummaryRecent work on the origin of soil polysaccharide and its biological stability in soil is reviewed. It is concluded that much of the constituent hexose and deoxyhexose sugars are of microbial origin, whereas the pentose sugars are derived from plant residues. The stability of soil polysaccharide in its native state is not related to its chemical composition but to its unavailability. This is caused by inaccessibility within undecomposed biological residues and to insolubility resulting from adsorption on clay, the formation of metal complexes, or tanning by soil humic substances. Complexing by metals and tanning may also inhibit enzymic hydrolysis.