bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE FATE OF APPLIED MOLYBDATE IN ACIDIC SOILS
Authors: SMITH B. H. , LEEPER G. W. 
Published: July 2006

SummarySodium molybdate, at the rate of 10 ppm Mo, was added to the surface of seven acidic soils which were then stored moist for 3 to 10 months. After storage, less than 4 per cent of the added Mo was leached through any of the soils by the equivalent of a 250 mm rain. Between 36 and 91 per cent of the added Mo could be extracted with 0·1M NaOH, this proportion decreasing with longer incubation. Up to 40 per cent resisted treatment with both H2O2 and NaOH, and most of this was extracted with dithionite plus citrate. It is concluded that Mo is not lost by leaching from acidic soils other than sands, but is adsorbed on sesquioxide surfaces and slowly changed into less soluble forms.
EFFECTS OF ADSORBED CATIONS ON PHYSICAL PROPERTIES OF TROPICAL RED EARTHS AND TROPICAL BLACK EARTHS
Authors: AHMED S. , SWINDALE L. D. , EL‐SWAIFY S. A. 
Published: July 2006

SummarySimilar relative effects were obtained for plastic limits, percentage stable aggregates, and hydraulic conductivities when a tropical red earth, consisting predominantly of kaolin and iron oxide, and a tropical black earth consisting predominantly of montmorillonite, were saturated with Ca, Mg, K, or Na ions or combinations of these. Plastic limits were independent of the nature of the saturation cations, but were significantly dependent upon clay type. Percentage stable aggregates of artificially prepared aggregates and hydraulic conductivity were affected by the four cations in the order Ca = Mg > K Na and were also significantly affected by clay type. Combinations of the four cations generally gave intermediate effects with Ca‐saturated soils more susceptible to deterioration by K or Na than Mg‐saturated soils. The results confirm the generally deleterious effect of Na ions and show that K ions have effects similar to Na on the properties investigated. They suggest that heavy potash fertilization without liming may lead to structural deterioration of these soils.
A COMPARISON OF POTASSIUM‐ACTIVITY RATIOS DERIVED FROM EQUILIBRATION PROCEDURES AND FROM MEASUREMENTS ON DISPLACED SOIL SOLUTION
Authors: MOSS P. 
Published: July 2006

SummaryDirect and indirect methods of determining cation ratios of natural soil solutions are reviewed. The problems of comparing their results are discussed. K activity ratios derived from measurements on ethyl alcohol‐displaced soil solutions and values determined for the same soils by the Q/I equilibration procedure were in excellent agreement. An approximate rapid Q/I procedure using two K‐Ca solutions whilst less precise in its determination of activity ratio would be useful for routine purposes. The use of a proportionality constant to calculate activity ratios is acceptable.
DETERMINATION OF pH, LIME POTENTIAL, AND ALUMINIUM HYDROXIDE POTENTIAL OF ACID SOILS
Authors: BACHE B. W. 
Published: July 2006

SummarypH values in CaCl2 suspensions of some acid Scottish soils increase with time, in some cases by 0·4 units in 24 h. This is attributed to proton uptake by a complex ion displaced into solution, and to obtain unambiguous values, pH in CaCl2 suspensions should be measured within an hour of making up the suspensions.In moderately to strongly acid soils, lime potential (LP) and aluminium hydroxide potential (AHP) vary with salt concentration and soil: solution ratio. Unique values for these ion‐activity ratios can be obtained by equilibration with a single solution only when the reference cations, i.e. (Ca2++Mg2+) for LP, and Al3+ for AHP, are the dominant exchangeable cations. Otherwise, equilibrium values should be obtained by interpolation from an exchange isotherm at the point where no exchange occurs, i.e. where Δ(Ca+Mg) = o for LP values and ΔA1 = o for AHP values.
A NEW ADSORPTION ISOTHERM FOR PHOSPHATE IN SOIL
Authors: GUNARY D. 
Published: July 2006

SummaryPhosphate adsorption data for 24 soils showed that although the Langmuir equation gave a good fit, there was significant curvature. Of the alternative equations examined, that of Freundlich provided a better description than that of Langmuir in 22 soils, but the best fit, accounting for more than 99·8 per cent of the variation in phosphate adsorption, was given by introducing a square‐root term:
image
where y= adsorbed phosphate, c= equilibrium concentration of phosphate in solution, B, A, and D are constants. The phosphate adsorption maximum, obtained from I/B, gave values in the range 325 to 1427 μg P/g soil which were 1·39 to 2·40 times those obtained from the Langmuir equation.The inclusion of a square‐root term in the Langmuir equation could be taken to imply that the soil will adsorb a little phosphate firmly, a slightly greater amount of phosphate less firmly, and so on until a limiting value is reached when all the components of the phosphate adsorption system are saturated.
DISTRIBUTION OF APATITE AND OTHER MINERAL INCLUSIONS IN A RHYOLITIC PUMICE ASH AND BEACH SANDS FROM NEW ZEALAND: AN ELECTRON‐MICROPROBE STUDY
Authors: CESCAS M. P. , TYNER E. H. , SYERS J. K. 
Published: July 2006

SummaryApatite, magnetite, ilmenite, and magnetite‐ulvöspinel inclusions were identified in certain primary minerals in a rhyolitic pumice ash and beach sands from New Zealand using an electron microprobe. In addition to being present in apatite inclusions, P was uniformly distributed throughout the matrix of plagioclase feldspars. Included apatite was particularly common in hypersthene and also occurred within Fe and Fe‐Ti rich phases in hypersthene. Quantitative data for Ca and P and the presence of Cl and F indicate the similarity in composition between the apatite inclusions and a chlorofluorapatite from Kola (U.S.S.R.). The coexistence of various mineral inclusions in hypersthene reflects magma composition, oxygen fugacity, and temperature conditions at the time of crystallization.The presence of included apatite and lattice‐P within certain primary minerals adequately explains the low results reported previously for total P in these samples, obtained by HClO4 digestion as compared to Na2O3 fusion. Apatite and lattice‐P present within magnetite, ilmenite, and magnetite‐ulvöspinel inclusions are expected to be pedogenically inert in weakly and moderately weathered soils.
THE ISOLATION OF NUCLEOSIDE DIPHOSPHATES FROM ALKALINE EXTRACTS OF SOIL
Authors: ANDERSON G. 
Published: July 2006

SummaryTwo pyrimidine nucleoside diphosphates have been isolated from sodium hydroxide extracts of soils. They were initially detected in fractions which had been separated by ion‐exchange chromatography, and were purified by a combination of ion‐exchange and paper chromatography. Their ultraviolet spectra indicated that one ester contained thymine and the other uracil, and this was confirmed by hydrolysis. The ratio of P to pyrimidine was 2, but their acid stability showed that the esters were not nucleoside‐5’ pyrophosphates. Both gave a positive reaction to a colour test for deoxypentose and comparison with reference samples prepared from calf‐thymus DNA showed that they were thymidine‐3′: 5’ diphosphate and deoxyuridine‐3′:5’ diphosphate.The nucleoside diphosphates may be artefacts, derived from polynucleotides by acid and alkaline hydrolysis, but their isolation confirms, for the first time, the existence in soil of characteristic structural units of DNA.
OCCURRENCE OF INOSITOL PHOSPHATES AND OTHER ORGANIC PHOSPHATE COMPONENTS IN AN ORGANIC COMPLEX
Authors: OMOTOSO T. I. , WILD A. 
Published: July 2006

SummaryA calcareous organic soil was extracted by shaking with Na+‐resin suspended in 0·2M acetyl acetone at pH 8·3. Fractionation of the fulvic acid on Sephadex G 25 gave (a) a high molecular‐weight component which contained inositol tetraand hexa‐phosphates and a sugar phosphate; (b) low molecular‐weight components which included the mono‐, di‐, and triphosphate esters of inositol and two sugar phosphates, but no free inositol phosphates. Inositol phosphates and sugar phosphates accounted for 30·2 per cent and 16·6 per cent of the soil organic P respectively. Our evidence indicates that these phosphate esters exist in an organic complex.
THE SPATIAL RESPONSE PATTERN OF GAMMA BACKSCATTER DENSITY GAUGES
Authors: DEVLIN G. , TAYLOR D. 
Published: July 2006

SummaryThis theoretical study shows that the sensitivity of the usual type of gamma backscatter gauge changes markedly for different soil volume elements according to their position with respect to the source and detector locations. There is a maximum in the so‐called detector region and a less important maximum in the source region. Calculation shows that 50 per cent of the total response of the instrument originates from 14 per cent by volume of the soil from a hemisphere of diameter d, d being the source‐detector separation. Since the response pattern of this type of backscatter gauge is far from uniform, it is necessary to consider the response patterns in planning the conditions of experiments involving these gauges to obtain the highest sensitivity. This is of particular importance in studying soils of a heterogeneous nature.
FURTHER STUDIES ON VARIABILITY OF SOIL CHEMICAL PROPERTIES: EFFICIENCY OF SAMPLING PROGRAMMES ON AN UNCULTIVATED BROWN EARTH
Authors: BALL D. F. , WILLIAMS W. M. 
Published: July 2006

SummaryAssessments of mean and range of variation for pH, loss on ignition, total nitrogen, and exchangeable K, Na, Ca, Mg, and Mn in the surface horizon of a uniform uncultivated soil have been made by nine sampling programmes. The selected soil was known to have spatial chemical variability of magnitudes widely found in other soils and situations. The effort involved in these programmes was, for sampling and analysis time, from 1.2 to 66 man‐days. The most complete sampling programme (275 samples each a composite of 10 cores), was used as a standard against which to compare the efficiency of the other programmes. Mean values for chemical quantities other than loss on ignition differed statistically significantly between programmes but there was no consistent trend with any particular programme. Knowledge of the range of variation is believed to be very important in interpretation of analyses and it is found that a programme using only 6 composite samples measures > 50 per cent of the range for most quantities and that a programme using about 25 composite samples measures at least two‐thirds to three‐quarters of the total range.
THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS
Authors: VAIDYANATHAN L. V. , NYE P. H. 
Published: July 2006

SummaryThe counter‐diffusion of phosphate against chloride was measured in a moisture‐saturated block of soil by following the efflux of phosphate into a limited volume of well‐stirred CaCl2 solution, of the same ionic composition as the soil‐pore solution except for a lower initial phosphate concentration. By varying this phosphate concentration effective diffusion coefficients over a wide range of depletion were measured. The fraction of labile phosphate desorbed, and the relation between phosphate desorbed and concentration of phosphate in the equilibrium solution were measured in the same experiments.Effective diffusion coefficients varied from 0.43 to 1.50 × 10‐4cm2 sec‐1, tending to decrease as depletion increased. Depletions ranged from about 0.3 to 25 per cent of the 32P exchangeable phosphate, which corresponded to a lowering of the solution concentration by about 30 to 65 per cent of the initial concentrations.Diffusive movement of phosphate in this soil can be accounted for by diffusion through the liquid pathway only. The effective diffusion coefficient can be predicted from phosphate desorbed in response to a change in the concentration of the equilibrium solution, and an impedance factor.
THE SHRINKAGE OF CLAY SOILS DURING IMPREGNATION BY POLYETHYLENE GLYCOLS
Authors: GREENE‐KELLY R. 
Published: July 2006

SummaryLinear measurements on a remoulded clay soil showed that the replacement of pore water by molten polyethylene glycol 6000 (PEG 6000) was responsible for the main contraction of the sample. Subsequent cooling of the wax resulted in only a small further shrinkage. The volumetric shrinkage of different clay soils on impregnation with PEG 6000 was about one‐half to three‐quarters of that on air‐drying. The contraction increased with increasing average molecular weight of the PEG fraction. Exchange of pore water with digol, O(CH2CH2OH)2, before impregnation with PEG 6000, decreased the total shrinkage by a further one‐third.
MICROMORPHOLOGY OF SOILS DEVELOPED FROM VOLCANIC ASH AND RIVER ALLUVIUM IN THE KOKODA VALLEY, NORTHERN DISTRICT, PAPUA
Authors: PAIN C. F. 
Published: July 2006

SummarySoils found on fan surfaces in the Kokoda Valley are derived from both volcanic ash and river alluvium. The alluvium is variable, some of it being mixed with volcanic ash. The main differences in the micromorphology of the soils appear to be related to the relative amounts of volcanic ash present in the soil profile. The plasma of soils formed on volcanic ash is isotropic in thin section. The plasma of alluvial soils exhibits increasing birefringence with decreasing amounts of volcanic ash. It is suggested that random structures in the clay fraction of the volcanic ash may account for its isotropic nature.
DISTRIBUTION OF CARBON DIOXIDE AND OXYGEN IN THE GAS PHASE OF AEROBIC SOILS
Authors: WOOD J. T. , GREENWOOD D. J. 
Published: July 2006

SummaryIt is shown that, under certain conditions, the increase in carbon dioxide partial pressure is proportional to the drop in oxygen partial pressure in the gas phase in fallow soils. The principal assumptions are that respiration is unaffected by lowering of oxygen partial pressure until very low levels are reached, and that the respiration quotient is constant. Previously reported measurements of the composition of gases extracted from soil are consistent with the theory.
AIR AND WATER PERMEABILITY OF COMPACTED UNSATURATED COHESIVE SOIL
Authors: BARDEN LAING , PAVLAKIS GEORGE 
Published: July 2006

SummaryThe air and water permeabilities of unsaturated cohesive soils have been measured in a modified triaxial cell permeameter which maintains separate continuity of both the air and water phases during permeation. Three different cohesive soils have been tested and the results interpreted in terms of the cluster concept of soil structure, which recognizes the existence of both macro‐ and micro‐pores. Both air and water permeability are shown to be dominated by the geometry and degree of saturation of the intercluster macro‐pores. Compression of the soil always reduces the air permeability but can increase the water permeability by increasing the membrane flow around the clusters. The relations between soil suction, occlusion of the air channels, and compaction water content have also been studied.
MOLECULAR SIZES AND FUNCTIONAL GROUPS OF HUMIC SUBSTANCES EXTRACTED BY 0.1M PYROPHOSPHATE FROM SOIL AGGREGATES OF DIFFERENT STABILITY1
Authors: DELL'AGNOLA G. , FERRARI G. 
Published: July 2006

SummaryAggregates from non‐cultivated soil and from cultivated soil enriched with mineral fertilizers or farmyard manure were separated into fractions of different diameter and stability. The humic substances extracted from each type of aggregate were subjected to gel‐filtration on Sephadex. The more stable aggregates had a higher content of Na4P2O7‐extractable humus and free iron hydroxides, and a predominance of humic substances of apparent molecular weight >100 000, whereas the less stable aggregates were richer in compounds of low molecular weight.Structure stability was lower in the cultivated soil than in the non‐cultivated, and in the soil with mineral fertilizers in comparison to that with farmyard manure. Humus of m.w. >100 000 had a COOH content twice as great and a phenolic OH content five times greater per unit of molecular weight than humus with m.w. <100 000. The former is the more suitable stabilizer of soil aggregates.
PROLONGED LEACHING OF ORTHIC BLACK Ah MATERIAL WITH WATER AND AQUEOUS EXTRACTS OF POPULUS TREMULOIDES AND P. BALSAMIFERA LEAVES
Authors: DORMAAR J. F. 
Published: July 2006

SummaryCylinders filled with Orthic Black Ah material were leached over a 2‐year period with distilled water or with aqueous extracts of aspen or black poplar leaves that were collected late in the growing season.Actual losses from the soil and chemical analyses of the leached soil indicated that the aqueous extract of aspen poplar leaves imposed greater changes on the chemical properties of the soil than did the extract of black poplar leaves. These changes were particularly noticeable for pH, total and exchangeable Ca, and 0.1N NaOH‐extractable C. The aqueous extract of aspen poplar leaves acidified the soil more strongly than the extract of black poplar leaves, even though there was little difference between the two extracts in polyphenol and polysaccharide content and the total acidity of the black poplar extract was about twice that of the aspen poplar extract.Aqueous extract of weathered aspen poplar leaves was no more effective than distilled water.
THE RELATION BETWEEN COST AND UTILITY IN SOIL SURVEY
Authors: BECKETT P. H. T. , BURROUGH P. A. 
Published: July 2006

SummaryThis paper discusses how to compare the utility of soil maps. For three contrasting areas, in Southern England, it compares the utilities of a number of single‐property and general purpose (series) soil maps, produced by free and grid survey, at map scales from 1 :20,000–1:70,000.The‘purity’of series mapping units increases with survey effort. Where the soil boundaries had fairly clear external expression free survey was superior to grid survey. On average the purity of maps by grid survey was higher than for maps by free survey at comparable survey effort.The uniformity of soil properties within mapping units was measured by relative variance (RV)= within‐unit variance/total variance, (1–RV) indicates the increased precision achieved by the soil map. It increased with survey effort. For series maps by free or grid survey (1–RV) depended on how closely soil properties were associated with profile classes, and on the extent to which soil boundaries could be mapped on their external expression. Free survey was preferred at scales between 1: 100,000 and 1:30,000, when the soil boundaries could be mapped on their external expression, (1–RV) for the profile classes on which the mapping units are defined puts a ceiling to the utility of series maps (grid or free) which is already nearly achieved at map scales near 1:25,000. Except for properties very poorly associated with profile classes, single property maps do not have great advantage over series maps at medium map scales, but they attain higher values of (1–RV) at scales greater than 1: 25,000.
THE RELATION BETWEEN COST AND UTILITY IN SOIL SURVEY
Authors: BECKETT P. H. T. , BURROUGH P. A. 
Published: July 2006

SummaryThe paper presents the final conclusions of this study. For the three areas surveyed it compares the costs and utilities of different procedures for producing soil maps at scales of 1: 20 000–1:70 000, using the criteria for utility discussed in Part IV. In particular it compares the utilities of different maps produced at the same cost, or the costs of producing different maps of equal utility, and the ratios of utility/cost for different survey procedures at different map scales.Within the limits of the approximations made and in areas presenting survey problems comparable to the area of lowland Britain surveyed, series maps by grid survey seem likely to give better value for money than series maps by free survey, at map scales greater than 1:50 000 in most landscapes and at all scales in some landscapes. There is a ceiling to the utility of general purpose maps of soil series, which is already nearly achieved at map scales of 1:25 000–1:20 000, and is surpassed only by single property maps by grid survey, at larger scales and at considerably higher cost.
NITROGEN, PHOSPHORUS AND SULPHUR CONTENTS OF HUMIC ACIDS FRACTIONATED WITH RESPECT TO MOLECULAR WEIGHT
Authors: SWIFT R. S. , POSNER A. M. 
Published: July 2006

SummaryTwo humic acids, extracted from widely different soils, have been fractionated with respect to molecular weight by means of gel chromatography. The resulting fractions were assayed for total nitrogen, amino acid nitrogen, phosphorus and sulphur.Nitrogen and phosphorus contents were greatest in the high molecular weight fractions and decreased considerably with decreasing humic acid molecular weight. The change in nitrogen content was accounted for mainly by the loss of amino acid nitrogen. By contrast, sulphur contents remained constant throughout the molecular weight range. These changes may reflect part of the process whereby nutrient elements, combined organically within humic acid, are made available for plant growth.
THE KINETICS OF HETEROGENEOUS ISOTOPIC EXCHANGE
Authors: PROBERT M. E. , LARSEN S. 
Published: July 2006

SummaryIsotopic exchange of phosphate ions between soil and solution was examined with particular emphasis on the slower reaction involving the incorporation of the tracer in the solid phase that follows the very fast exchange reaction between the solution and the surface of solid. Experimental data fitted both an equation composed of a sum of exponentials and a much simpler two‐constant equation. The goodness of fit was similar in each case but it was concluded that the exponential type of equation was not useful as a means of elucidating the mechanisms involved. The two‐constant equation may be derived from the kinetics of crystallization and recrystallization processes, and therefore provides an interpretation which is amenable to experimental verification.
THE EFFECT OF SOIL FACTORS ON THE EXTRACTION OF SOIL ORGANIC MATTER BY ANHYDROUS FORMIC ACID
Authors: JONES M. J. , PARSONS J. W. 
Published: July 2006

SummaryTwenty‐five soils, having a wide range of organic matter contents, were extracted with anhydrous formic acid containing 10 per cent acetylacetone, and the extracted material precipitated in two fractions with diisopropyl ether. Precipitates comprised from 5.1 to 51.1 per cent of the original soil organic matter, the proportion extracted tending to be greatest from acid soils of fairly high organic matter content and least from neutral or slightly alkaline soils of low organic matter content. Soil clay content appeared to have no effect on the efficiency of organic matter extraction, but was the most important soil factor governing the proportion of the total soil‐N extracted. Amounts of N extracted ranged from 10.2 to 57.8 per cent of the original soil N content, extraction efficiency being greatest with soils of low clay content and low pH. There was evidence to suggest that soil clay afforded some protection to N compounds against extraction. The results indicate that formic acid/acetylacetone is most effective with soils in which much of the organic matter is only partly humified.