bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE RATE OF IMMOBILIZATION OF APPLIED PHOSPHATE IN RELATION TO SOIL PROPERTIES
Authors: LARSEN S. , GUNARY D. , SUTTON C. D. 
Published: July 2006

SummaryThe fate of superphosphate applied at 500 and 1,000 Ib P2O5 per acre in a field experiment with twenty‐four sites was followed by measuring changes in the L‐value over 5 years. The L‐value decreased exponentially at a rate that was expressed as the time in years for half the applied phosphate to become non‐labile (the half‐life). The two fertilizer rates gave similar values in most of the experiments and half‐life values were satisfactorily measured for nineteen soils; the values ranged from 1 to 56 years.Some relationship between half‐life values and a number of soil properties was sought. The only significant correlation was with the hydrogen‐ion concentration, from which it is suggested that the decrease in labile phosphate could be the result of the formation of a crystalline basic calcium phosphate at a rate that increases with soil pH.
THE RETENTION OF AMORPHOUS, COLLOIDAL ‘FERRIC HYDROXIDE’ BY KAOLINITES
Authors: FOLLETT E. A. C. 
Published: July 2006

SummaryThe sorption and distribution of amorphous colloidal ‘ferric hydroxide’1 particles on the surfaces of kaolinite flakes were studied by electron microscopy. The sorption reaction was crystallographically specific with particles observed only on basal plane surfaces and was unaffected by the presence of excess NH4+, Ca++, or Al+++ ions. Cationic surface‐active agents prevented the reaction. Differences observed in colloid distribution and density on the introduction of a competing surface indicated that only one surface of a flake was attracting colloid particles and similar experiments with quartz and gibbsite suggested the silicatetrahedra surface of kaolinites as the probable site of colloid fixation. The distribution of colloid was unaffected by pH variation, saturation with ammonium acetate, prolonged washing, or ultrasonic vibrations. The colloid was removed only by extraction with sodium dithionite.
OBSERVATIONS ON THE BIOLOGICAL DEVELOPMENT OF MACROPORES IN SOILS OF ROMNEY MARSH
Authors: GREEN R. D. , ASKEW G. P. 
Published: July 2006

SummaryMany of the soils developed on Recent alluvium in Romney Marsh have abundant interconnecting pores, holes, and cavities in their subsurface horizons formed by the activity of roots, ants, and earthworms. Ants are considered to be the dominant agents in forming highly developed underground systems of galleries and chambers. These features are apparently continuous over large areas and are not restricted to any particular soil, but occur on differing soils with a considerable range of pH, salinity, texture, and fluctuations of water‐tables. Consequently, many of the soils have drainage and other characteristics that cannot be deduced from a consideration of texture or structure (pedality) alone. The characteristics of these macropores, as revealed by the infiltration into the soil of cast‐forming materials such as plaster of Paris, are described, and their origin, distribution, and significance in relation to land use are discussed.
THE HUMIC ACIDS EXTRACTED BY VARIOUS REAGENTS FROM A SOIL
Authors: POSNER A. M. 
Published: July 2006

SummarySolutions of o.5N NaOH, o.1M pyrophosphate (pH 7), and o.5N Na(CO2−3/HCO−3) [2:1] extract humic acid and organic matter from a soil with decreasing effectiveness.Pre‐treating the soil with o.1N HC1 increased the yield of humic acid obtained with the alkaline extractants. An additional pre‐treatment with a mixture, which was normal with respect to HC1 and HF, gave a slight reduction in yield.Increasing the temperature of extraction increased the yield of humic acid.The total C extracted was usually in excess of the humic acid recovered. The difference was obtained as ‘humins’.The sum of the Fe2O3, SiO2, and A12O3 contents of the humic acids was always less than 2 per cent. Where the extraction was carried out at room temperatures the SiO2/Al2O3 ratio suggested that they might be present as clay mineral. When extraction was carried out at an elevated temperature this ratio was altered.Humic acids of low ash content (0.1–0.5 per cent) could be obtained by the use of hot reagents. Of all the extractants used at room temperature, pyrophosphate produced the humic acid of lowest ash content (∼ 0.2 per cent).The Fe2O3 content of the humic acids was not correlated with their SiO2 or A12O3 content.The N‐content of the humic acids was substantially independent of the method of extraction.The cation‐exchange capacities (C.E.C.), average pK values and range of pK values, have been determined from the titration curves of the humic acids. These quantities vary with the method of extraction.There are good correlations between cation exchange capacity and both average pK values and the range of pK values.The within‐molecule variation of pK values appears to be greater than the between‐molecule variation.No correlation exists between C.E.C. and Fe, Al, Si, and N content of the humic acids.
ISOTOPIC EXCHANGE OF FIXED AMMONIUM
Authors: NEWMAN A. C. D. , OLIVER S. 
Published: July 2006

SummaryThe isotope 15N was used to study the rate of exchange between unlabelled NH4‐hydrobiotite and labelled solution NH4.Most of the isotopic dilution occurred within 10 minutes of adding the solution to the solid, but even after 13 days less mineral‐NH4 had exchanged with isotope than was removed by several extractions with KC1 solution.NH4 remaining in the mineral after extraction with KC1, conventionally named ‘fixed ammonium’, contained some isotope which was sorbed without release of unlabelled NH4; the fixed ammonium was, therefore, not isotopically exchangeable. The sorption was shown to result from incomplete ammonium saturation of hydrobiotite, isotope slowly replacing interlayer cations trapped by lattice collapse.The rate of sorption was initially controlled by a temperature‐dependent diffusion process for which the activation energies were between 9 and 13 kcal/ mole. In the later stages of the reaction the rate became progressively slower than predicted by the diffusion equation, and analysis of the kinetics suggested that, ultimately, exchange of cations at the sorption sites was the rate‐limiting process.
STUDIES ON THE DECOMPOSITION OF PLANT MATERIAL IN SOIL
Authors: JENKINSON D. S. 
Published: July 2006

SummarySoil samples taken during an experiment on the decomposition of 14C‐labelled ryegrass in soil under field conditions (see Part I) were air‐dried, irradiated, exposed to CHCl3 or CH3Br vapours, oven‐dried or autoclaved. After these treatments the soils were inoculated, incubated, and the output of CO2 measured. All these methods of partially (or, in some cases, completely) sterilizing soil rendered a small heavily labelled fraction of the soil organic matter decomposable. This fraction is postulated to be the soil biomass. Treatments involving heat or irradiation rendered small additional amounts of the soil organic matter decomposable (by processes other than the killing of organisms).Incubating unsterilized soil with partially sterilized soil did not decrease evolution of CO2. This suggests that partial sterilization does not increase mineralization by destroying toxic substances that inhibit microbial growth, or by disturbing a host: predator balance in the unsterilized soil.The longer the labelled ryegrass was allowed to decompose in the field, the less labelled‐CO2 was evolved after partial sterilization. In contrast, the same amount of unlabelled‐CO2 was evolved from a soil that had been incubated 1 or 4 years with ryegrass. The labelled part of the biomass is considered to be largely zymogenic (with a half life of approximately 1.5 years), the unlabelled part largely autochthonous, remaining almost constant over the 3‐year period.It is suggested that the size of the soil biomass can be roughly estimated from the size of the flush of CO2 after CHCl3 vapour treatment. Calculated on this basis, 2.3–3.5 Per cent the unlabelled‐C in these soils (i.e. the C present in the soil before the labelled ryegrass was added) was in the biomass. Of the original ryegrass C added, 10–12 per cent was in the biomass after 1 year, decreasing to 4 per cent after 4 years.
QUANTITATIVE DETERMINATION OF CALCITE AND DOLOMITE IN SOILS
Authors: PETERSEN G. W. , CHESTERS G. , LEE G. B. 
Published: July 2006

SummarySoil carbonates were differentiated into calcite and dolomite and determined quantitatively by a method based on their differential solubilities in 0.30 M Na citrate—0.14 M Na dithionite. Calcite dissolution was favoured by the acidic and chelating nature of the citrate. Prior destruction of iron‐oxide coatings on soil carbonates and/or iron oxide‐carbonate complexes by the citrate‐dithionite iron‐removal process was necessary for complete calcite dissolution. This method consisted of a total carbonate determination, selective dissolution of calcite with a citrate‐dithionite extraction, and determination of dolomite by difference.Citrate‐dithionite soluble calcite and dolomite are calculated from the quantities of extracted Ca and Mg. Soil exchangeable Ca and Mg may interfere and should be removed prior to citrate‐dithionite extraction on soils of high exchange capacity and/or low carbonate content. Interferences arising from dissolution of non‐carbonate Ca‐ and Mg‐containing soil minerals were considered negligible.Replicate analyses of a broad spectrum of samples suggest that the method is highly satisfactory for the determination of calcite and dolomite contents of soils and sediments of very variable composition. The occurrence of dolomite appears to be related to dolomitic source areas and is detritial whereas calcite is primarily reprecipitated (secondary) carbonates, although some calcite may be of detritial nature, e.g. shell materials or calcitic limestone drift.
THE CORRELATION OF SURFACE AREA WITH OTHER PROPERTIES OF NINETEEN BRITISH CLAY SOILS
Authors: FARRAR D. M. , COLEMAN J. D. 
Published: July 2006

SummaryThe total and external surface areas of nineteen British clay soils were determined from measurements of their water and nitrogen adsorption respectively. In addition, four physical and chemical properties of these soils were determined; liquid limit, plastic limit, cation exchange capacity, and clay content.The correlation between these six measured properties was examined. Total surface‐area, liquid limit, and cation exchange capacity, had correlation coefficients of 0.90 or greater. This is sufficiently high to enable an indication of these three properties to be obtained from measurements of any one of them.The correlation between these three properties and the rest was slightly lower for the plastic limit, and considerably lower for the clay content and external surface‐area, although all were significant at the 5 per cent level.
ION EXCHANGE IN SOILS FROM THE ION PAIRS K–Ca, K–Rb, AND K–Na1
Authors: DEIST J. , TALIBUDEEN O. 
Published: July 2006

SummaryIsotopic exchange of 43K, 24Na, 86Rb, and 45Ca was used to measure the equilibria between some arable soils and mixed chloride solutions of the ion pairs, K–Ca, K–Rb, and K–Na; the results were interpreted by a thermodynamic treatment of the exchange isotherm (Gaines and Thomas, 1953). The cation exchange capacities of the soils were not constant for the three ion pairs and decreased appreciably with K‐saturation in the K–Ca systems because Ca ions were trapped inside the interlayer spaces. That soils preferred K to Na in the K–Na systems and Rb to K in the K–Rb systems, was explained in terms of the standard free‐energy changes of the exchange reactions.The activity coefficients of the adsorbed ions, f, changed with K‐saturation differently for the three ion pairs: fNa and fCa decreased continuously with increasing K‐saturation whereas fRb remained almost constant. However, with increasing K‐saturation, fK increased in the K–Na systems, remained unchanged in the K–Rb systems, and first increased and then decreased in the K–Ca systems. These changes are interpreted in terms of the effect of the various ions on the interlayer space of 2 : 1 type clay minerals and the possible distribution of adsorbed ions between the Gouy and Stern layers.
MEASUREMENT OF SOIL MOISTURE IN THE FIELD BY NEUTRON MODERATION
Authors: LONG I. F. , FRENCH B. K. 
Published: July 2006

SummaryDesign, calibration, working precautions and field use of a soil‐moisture meter are described. The probe carries a source 241Am‐Be and a detector 10BF3 in an Al case, 3.4 cm diam and 17 cm long. Source and detector are as close to each other as possible, so giving a desired linear relationship between thermal neutron count and the volumetric water content around the probe. The portable sealer incorporates some new features of circuit design that lead to ease of operation and small size: it weighs 5 kg. Factors involved in calibration or the interpretation of a calibration curve are: resolving time of the sealer, the volume of soil explored by the neutrons, the effect of a moisture gradient, and the possible effect of elements other than hydrogen.Field trials were in two groups. In 1962 and 1963 frequent measurements were made in bare clay soil and under a nearby barley crop: from the profiles, the extraction of water from the bare soil was limited to the top 30 cm, but the barley roots took water out at least as deeply as the maximum depth of measurement then possible, 90 cm. In 1964 similar measurements under first‐year Timothy and Meadow Fescue, irrigated and non‐irrigated, showed that the total water abstracted by each was nearly the same, but the Timothy took most of its water from the top 40 cm of the profile, whereas the Fescue took more water from the lower depths. Combining the estimated deficits with known rainfall gives values of periodic evaporation in good agreement with aerodynamic estimates based on temperature, humidity, and wind profiles above the crop, and in fair agreement with potential evaporation‐rates calculated from routine weather records.
THE INFLUENCE OF TEXTURE ON THE MOISTURE CHARACTERISTICS OF SOILS
Authors: SALTER P. J. , WILLIAMS J. B. 
Published: July 2006

SummaryThe available‐water capacity (AWC) of soil profiles in the field may be estimated by (a) measuring the thickness of each soil horizon; (b) assessing its texture; and (c) summing the products of the thickness of each horizon and the mean values of AWC for the relevant textural classes. (This mean value of AWC was calculated from the average particle‐size composition and from a relationship between particle size composition and AWC.) Estimates of AWC using this method were compared with measured values for each of 39 soils. When a 21 textural‐class system was used to describe the soils, the mean error (the error of the estimated AWC value relative to the measured value) was ±10 per cent and with a 12 class system the mean error was ±17 per cent.
DIRECT MEASUREMENTS OF THE DISTRIBUTION OF OXYGEN IN SOIL AGGREGATES AND IN COLUMNS OF FINE SOIL CRUMBS
Authors: GREENWOOD D. J. , GOODMAN D. 
Published: July 2006

SummaryThe micro electrode of Evans and Naylor was modified to permit measurements of oxygen concentration in soil and was used to determine the distribution of oxygen in (a) agar which contained yeast and glucose and served as a model of a respiring water‐saturated soil; (b) saturated spherical soil aggregates; (c) partly saturated columns of fine soil crumbs. Measurements in (a) and (b) but not in (c) agreed closely with predictions by diffusion theory. The disagreement appeared to result from water being unevenly distributed in the columns.
EVALUATION OF METHODS FOR DETERMINING AVAILABLE SOIL POTASSIUM BASED ON POTASSIUM UPTAKE BY PLANTS1
Authors: FEIGENBAUM SALA , HAGIN J. 
Published: July 2006

SummaryMeasurements of exchangeable K, percentage of exchangeable K in the total exchange capacity, K extracted in a CaCl2 solution, and the change in free energy of exchange of K for Mg and Ca (ΔF) were compared as methods for the evaluation of available K in soils. The evaluation was based on the K uptake of plants in a pot exhaustion experiment. The ΔF value was best correlated with the K uptake of the plants. A good correlation was found between the logarithms of the exchangeable K expressed as a percentage of the cation exchange capacity and ΔF values.
GENESIS, MINERALOGY, AND RELATED PROPERTIES OF WEST INDIAN SOILS
Authors: AHMAD N. , JONES R. L. , BEAVERS A. H. 
Published: July 2006

SummaryThe Montserrat series is one of the most fertile of tropical soils. Substantial amounts of exchangeable K, available P, and favourable organic matter content and distribution contribute to its unique properties. P occurs in amounts ranging from 0.4 to 0.6 per cent, about 75 per cent of which is inorganic with Fe phosphates making up the bulk. Truog's reagent almost quantitatively extracts Ca phosphate and Bray's and Olsen's reagents extract mainly Al phosphate. Exchangeable K is derived from glauconite. High exchangeable Ca and Mg contents derived from weathering of carbonates impart a favourable pH to the soil for plant growth. Exceptional structural stability to 120 cm depth is associated with high free iron oxide, organic matter, and Ca contents.The outstanding feature in mineral weathering is the rapid transformation of glauconite through vermiculite to kaolinite and the formation of goethite. Considerable interlayering occurs between vermiculite with sesquioxide coatings and mica‐vermiculite interlayers. Much of this weathering occurs in the calcareous, oxidized, friable parent rock.The features of the Montserrat series described above substantiate its classification as a Brown Earth (Mollisol).
SULPHATE DISTRIBUTION IN SOLONETZIC SOIL WITH A WATER TABLE
Authors: KHAN S. U. , WEBSTER G. R. 
Published: July 2006

SummarySoil columns were used to study sulphate distribution in Thin Duagh Loam soil as influenced by the presence of a water table. The concentration pattern showed that retention was greater in the surface soil than at lower depths. The data suggest that sulphate tends to move more slowly than water in soil.
SOIL SUCTION BY THE RAPID METHOD: AN APPARATUS WITH EXTENDED RANGE
Authors: DUMBLETON M. J. , WEST G. 
Published: July 2006

SummaryIn the rapid method of measuring soil suction the sample is placed on a porous plate attached to a capillary flow tube containing water. A suction is applied to the flow tube and rapidly adjusted to equal the suction of the soil, without change of soil‐moisture content. A form of the apparatus is described which has provision for very convenient and rapid adjustment of the applied suction by the use of either a vacuum pump or an air piston. The range of the apparatus is extended from the usual limit of pF 3 up to pF 3.35 by applying air pressure to a chamber enclosing the sample, using a hand pump. Suction curves for a sand, a silty clay, and a heavy clay illustrate the application of the apparatus, which can readily be constructed in a form suitable for field use.
CHANGES IN SOIL PROPERTIES ASSOCIATED WITH THE REMOVAL OF IRON AND ALUMINIUM OXIDES
Authors: DESHPANDE T. L. , GREENLAND D. J. , QUIRK J. P. 
Published: July 2006

SummaryRed soils representing the major groups in which iron oxides are thought to exert a favourable effect on physical properties, have been treated with Na‐dithionite and citrate, or Na‐dithionite and 0.05 n HC1. These treatments removed the free iron oxides and some aluminium oxides and silica. Changes in the physical properties of the soils were measured by permeability, wet‐sieving, mechanical dispersion, and swelling methods. These were compared with the changes induced by corresponding control treatments in which the soils were treated with Na2SO4 and Na‐citrate, or Na2SO4 and 0.05 n HC1. The control treatments extracted some aluminium oxide and minor amounts of iron oxides and silica. In general, the control treatments decreased the stability of aggregates, increased the proportion of clay and silt but had little effect on the swelling. The treatments, which removed all the free iron oxide, caused no changes in excess of those due to the controls. The specific surface areas of samples treated with dithionite and acid, or sulphate and acid were determined by nitrogen adsorption methods. Removal of free iron oxides led in all but one instance to a reduction in the specific surface area, whereas sulphate and acid invariably increased the specific areas of the samples. The results show that most of the free iron oxides in these soils are present as small particles having little effect on the physical properties of the soil. The changes in physical properties brought about by dilute acid treatment indicate that the ‘active’ oxides in these soils are composed partly or wholly of the aluminium, iron, and silicon oxides which are readily soluble in dilute acid.
BASALTIC SOILS OF SOUTH‐WEST ICELAND. II
Authors: HELGASON BJARNI 
Published: July 2006

SummaryData for mechanical and chemical analyses are presented with tabulated mean and median values based on fifty‐five freely drained and ten poorly drained soils.The soils are relatively coarsed textured. The sand content of the mineral fraction is about 70 per cent (mean value) for freely drained and about 45 per cent (mean value) for poorly drained soils.Organic C is generally high in freely drained soils but relatively low in poorly drained soils, because of accumulating aeolian matter in the latter group, mean values are 8.2 in freely drained and 16.5 per cent in poorly drained soils. The C/N ratio is about 15 for each soil group.The cation exchange properties including pH seem to be dominated by organic matter, which may contribute to the total CEC of the soils about 165–300 me/100 g C. CEC of soils is usually 40–50 me/100 g. For some selected soils CEC of the separated mineral fractions was confirmed experimentally through ammonia retention.The pH level, especially of the freely drained soils, is relatively high (mostly 5.4–6.3) in spite of low degree of base saturation (mostly 10–30 per cent), a characteristic probably derived from the parent material. A highly significant correlation exists between pH and organic C.Proportionally exchangeable Ca seems low, while Mg and Na may be abundant. In some soils exchangeable Mg may exceed Ca.
USE OF RADIOACTIVE 59Fe FOR TRACING SOIL PARTICLE MOVEMENT
Authors: COUTTS J. R. H. , KANDIL M. F. , NOWLAND J. L. , TINSLEY J. 
Published: July 2006

Summary 59Fe appeared to be a suitable tracer for investigating soil particle movements and experimental results have demonstrated quantitatively that, when a dilute radioactive FeCl3 solution is applied to soils of varied texture, this isotope is firmly absorbed, and shows little tendency to downward movement by leaching. Addition of the chelating compound di‐ethylene triamine penta‐acetic acid (DTPA) greatly improves the uniformity of absorption.The surface movement of labelled soil particles was readily detected by direct scintillation counting of grid reference points over trays of soil exposed in the field or of core samples transported to the laboratory, and less sensitively by autoradiographs on X‐ray film applied to the surface of ground plots.Under the summer and winter weather conditions prevailing at Aberdeen, the displacement of soil from bare surfaces by rain splash is markedly affected by wind speed and direction. Even with light showers, relatively low wind speeds and slopes not exceeding 6°, some of the labelled soil particles migrated distances of 60 cm from the treated areas in the centre of ground plots 2 m square.