bluuebunny/crossref_metadata_2025_split huggingface dataset:
A SOIL CATENA ON GRANITE IN SOUTHERN RHODESIA
Authors: WATSON J. P. 
Published: July 2006

SummaryA catena on the Mid‐Tertiary surface near Salisbury, Southern Rhodesia, has developed over granite. Both land form and rock form indicate a two‐cycle landscape. The climate is sub‐tropical with a 33‐in. rainfall and the vegetation is a variant of Braclzystegia savannah woodland. Profiles of good and imperfect drainage have three main horizons, namely, M (mineral); over, F/S (ferricrete and stones); over, W (weathered rock) horizons. Poorly drained soils exhibit G (gley) horizons. The W horizon of a hill‐top soil comprises material at an early weathering stage below 12 ft having a platy structure, well‐developed clayskins, and fresh minerals, but older material above that depth does not correspond to Van Wambeke's criteria for ante‐Pleistocene materials. Dynamic soil‐forming processes include lateral movement of the M horizon by sheetwash and truncation of the W horizon by insect activity.
DISTRIBUTION OF FORMS OF NITROGEN IN A PODZOLIC SOIL PROFILE FROM GARPENBERG, CENTRAL SWEDEN
Authors: NÔMMIK HANS 
Published: July 2006

SummaryThe chemical nature and distribution patterns of the forms of N in a podzolic soil profile from central Sweden, developed under a stand of Norway spruce, were studied. Total N, native fixed NH4, acid hydrolysable‐N, and the amounts of ammonia, hexosamine, and amino‐acid N in the hydrolysate were determined. From 17 to 27 per cent of the N was insoluble in 6N HC1, the highest percentage being in the A2 horizon. Amino‐acids in the acid hydrolysates decreased from 50 per cent of the total N content of the soil in the humus layer (A0) to 24 per cent in the B horizon. Amino‐acid composition varied little in samples from different horizons. Hexosamine‐N was 11–14 per cent of the total soil N, tending to increase with depth. Approximately 15 per cent of the total soil N was found in the soil hydrolysate as NH4. Values for native fixed NH4 extracted by N HF: N HCl were 34–80 ppm but were reduced to 10–17 ppm when corrected for the NH4 released by N HCl only. The figures thus obtained are considerably lower than those reported by other workers.
PROPERTIES AND COMPOSITION OF THE BACTERIAL FLORA OF A PINE FOREST SOIL
Authors: GOODFELLOW M. 
Published: July 2006

SummaryA study was made of the qualitative and quantitative distribution of aerobic heterotrophic bacteria in the two mineral horizons of a developing podsol soil under Pinus. There was no significant difference in the total numbers or in the kinds of bacteria between the two horizons. In the acidic A1 horizon (pH, 3.6) Bacillus spp. comprised 58 per cent of the population, the remainder being composed of Gram‐negative rods (15 per cent), pleomorphic rods (14 per cent), Gram‐positive cocci (10 per cent) and streptomycetes (3 per cent). The corresponding figures for the C horizon (pH, 8.6) were Bacillus (23 per cent), Gram‐negative rods (37 per cent), pleomorphic rods (10 per cent), Gram‐positive cocci (17 per cent) and streptomycetes (13 per cent). These differences in distribution could not be related to any one environmental factor. The data from this investigation lend support to the view that different soil types can be distinguished by their bacterial floras. Bacillus subtilis, B. cereus and the Gram‐positive cocci were biochemically and fermentatively active and many of the streptomycetes were able to degrade complex organic molecules. The Gram‐negative and pleomorphic forms were apparently metabolically inactive.
A DUNE CATENA ON THE CLAY PLAINS OF THE WEST CENTRAL GEZIRA, REPUBLIC OF THE SUDAN
Authors: WILLIAMS M. A. J. 
Published: July 2006

SummaryFixed dunes occupy 400 000 acres in the west central Gezira. Isolated dunes occur sporadically through the central Gezira, and trend NW from Sennar on the Blue Nile to El Geteina on the White Nile. They probably originated as channel deposits laid down by former distributaries of the Blue Nile. Minor aeolian re‐sorting took place, and was followed by plant colonization and dune stabilization. Erosion of the dunes is locally active, resulting in exposure of the underlying clays.The catena comprises leached sands (Psammustents) on the dune crests and illuvial loams and clays (Orthustents) in the swales. Swale soils contain pedogenetic and relict lacustrine carbonate.The catena is often superimposed upon former soils, resulting in polygenetic profiles.
ALPINE PODZOL SOILS ON THE BEN LAWERS MASSIF PERTHSHIRE
Authors: STEVENS J. H. , WILSON M. J. 
Published: July 2006

SummaryCharacteristics of the soils include well‐defined horizons, very low pH values and base saturation percentages, and a slight but general increase in the silt‐plusclay content down the profile. X‐ray diffraction shows that the soil clays are rich in mica and chlorite with subsidiary amounts of kaolinite, goethite, and lepidocrocite. The general distribution of the clay minerals in the profiles studied suggests that the weathering of chlorite leads to the formation of kaolinite in the A horizons and to the accumulation of crystalline iron‐oxide minerals in the B horizons. The presence of kaolinite, taken in conjunction with recent clay mineral studies of Scandinavian and Canadian podzols, indicates that the Ben Lawers soils may pre‐date the last glacial period.
RATE PROCESSES IN THE DESORPTION OF PHOSPHATE FROM SOILS BY ION‐EXCHANGE RESINS
Authors: VAIDYANATHAN L. V. , TALIBUDEEN O. 
Published: July 2006

SummaryPhosphate extracted by ion‐exchange resins in the chloride and sodium forms from a deep river‐gravel soil under widely varying conditions is always from the isotopically exchangeable or‘labile’ pool. At any reaction time, a constant fraction of this pool is desorbed by the chloride form of the anion‐exchange resin alone, irrespective of the pH and phosphate manuring of the soil. If, however, a sodium: cation exchange resin is included, increasing fractions of the‘labile pool’ are desorbed with decreasing soil acidity.Phosphate desorption by the anion‐exchange resin alone and with the cation exchange resin is shown to be‘particle‐diffusion’ controlled in the anion exchange resin and neither a‘chemical reaction’ nor a‘film‐diffusion’ mechanism. Over the pH range 4·5–8·5, values between 4·8 and 0·9 × 10‐9 cm2 sec‐1 were calculated for the interdiffusion coefficient of the phosphate: chloride exchange process in the resin.The isotopically exchangeable phosphate in the soils seems to behave like sparingly soluble or weakly dissociating compounds towards ion‐exchange resins and its rate of desorption depends on the nature and composition of the resins.
THE USE OF ORIENTATION DIAGRAMS IN DESCRIBING PLASMIC FABRICS IN SOIL MATERIALS
Authors: HILL I. D. 
Published: July 2006

SummaryOrientation diagrams are used to show differences in the orientation of birefringent domains in the S‐matrix, and in sub‐cutanic features of the vo‐insepic fabric of two West Indian soils. Such orientation diagrams could prove useful in helping to characterize plasmic fabrics.
EFFECTS OF ADSORBED CATIONS ON PHYSICAL PROPERTIES OF TROPICAL RED AND TROPICAL BLACK EARTHS
Authors: EL SWAIFY S. A. , AHMED S. , SWINDALE L. D. 
Published: July 2006

SummaryThe liquid limits, degrees of dispersion, and moisture retention of a Tropical Red Earth consisting predominantly of kaolin and iron oxides were independent of the nature of the saturating cation. The same three properties of a Tropical Black Earth consisting predominantly of montmorillonite were dependent upon the nature of the saturating cation, with Na giving the highest values and K the lowest. Ca and Mg gave intermediate and essentially equal values.The effects of the four cations have generally been explained in terms of the balance between attractive and repulsive forces in soil solutions and pastes. Unexpected behaviour due to K saturation has been explained by specific adsorption of K in a manner similar to but weaker than irreversible fixation.Linear regression equations were derived to express the dependence of the three properties on the saturating cations. The regression equations, which were all highly significant, show that the four cations examined were acting independently. Small positive interactions between Na × K, Mg × K, and Ca × K indicated that the effect of K fixation was important only when the Black Earth was nearly saturated with K ions.
INFRA‐RED SPECTRA AND DIFFERENTIAL THERMOGRAMS OF LIGNINS AND SOIL HUMIC MATERIALS SATURATED WITH DIFFERENT CATIONS
Authors: THOMPSON S. O. , CHESTERS G. 
Published: July 2006

SummaryComparison of infra‐red spectra of lignins and humic materials obtained before and after saturation with Cu showed that Cu saturation induced changes in the shape of the OH absorption bands and pronounced shifts in the C=O (1700 cm‐1) bands to lower frequencies.Differential thermograms indicated that Cu and Ca saturation reduced the thermal stabilities of lignins and humic materials. There was more reduction in stability with Cu than with Ca saturation and with lignins than with humic materials.
THE NATURE OF THE NITROGEN COMPOUNDS IN SOIL ORGANIC MATTER EXTRACTED BY ANHYDROUS FORMIC ACID
Authors: JONES M. J. , PARSONS J. W. 
Published: July 2006

SummaryOrganic matter extracted with 9 : 1 formic acid : acetylacetone from twenty‐five soils of widely varying organic content and precipitated with excess di‐isopropyl ether was hydrolysed with 6N HC1. The relationships between the proportions of acid‐soluble N, acid‐insoluble N, amino‐N, and ammonium‐N thus produced, and the properties of the original soil were examined. The distribution of N in acid hydrolysates was similar to that reported in the literature for material isolated by neutral and alkaline extractants. The relatively large proportion of N released as ammonium‐N from organic matter obtained from soils of high pH and low C : N ratio may derive from organically fixed ammonia. The low levels of amino‐N in organic matter extracted by formic acid from soils of high clay content imply the existence of clay‐amino complexes that resist extraction although formation of such complexes during extraction cannot be ruled out.
THE MEASUREMENT AND PREDICTION OF AVAILABLE WATER CAPACITY OF FERRALLITIC SOILS IN UGANDA
Authors: PIDGEON J. D. 
Published: July 2006

SummaryField capacity was measured directly, and soil moisture characteristics were determined on undisturbed cores, for a wide textural range of ferrallitic soils in Uganda. The initial moisture conditions of the soils were shown to affect results and thus standardized procedures were adopted for field and laboratory determinations. Laboratory estimates of field capacity for undisturbed and disturbed samples were shown to be unreliable, but a correction factor was found which improved them. There was no single moisture tension for undisturbed core samples that corresponded to field capacity.Particle‐size composition could be related to field capacity, permanent wilting‐point, and available water capacity by multiple regression equations having correlation coefficients of 0.96, 0.98, and 0.88 respectively. The relationships predicting available water capacity were different from those found for soils in England, but those for field capacity and permanent wilting‐point were similar. Particle‐size analyses were carried out using three methods of dispersion of different efficiencies. Particle‐size composition following gentle dispersion by shaking soil with distilled water was poorly correlated with moisture‐holding properties. There was little advantage in using vigorous ultrasonic dispersion compared with overnight shaking with sodium hexametaphosphate.Two soils formed on alluvial deposits with kaolinite the only clay mineral, and one soil with montmorillonite the dominant clay mineral, showed markedly different relationships between moisture‐holding properties and particle‐size composition.
THE ALKALINITY OF ALKALI SOILS
Authors: VAN BEEK C. G. E. M. , VAN BREEMEN N. 
Published: July 2006

SummaryThe theoretically derived equation: log Alk–pH = log Pco2–7.82 describes the relation between three easily estimated parameters, viz. the composition (alkalinity), CO, partial pressure and the pH of the soil solution. This equation is also important for understanding the formation of alkaline soils. The concept of residual alkalinity, i.e. the difference between the alkalinity and the total concentration of the divalent cations in the soil solution (on an equivalent basis) is introduced. In a closed basin with excess evaporation over precipitation highly alkaline soils, i.e. soils with a pH above 8 to 8.5, develop if the inflowing water has a positive residual alkalinity. A number of processes, such as weathering, oxidation and reduction, cation exchange, precipitation, addition of neutral salts, evaporation, which may influence the alkalinity and residual alkalinity of natural waters and soils are discussed briefly.
OBSERVATIONS ON THE SOIL‐WATER REGIMES IN A DRAINED CLAY SOIL
Authors: TRAFFORD B. D. , RYCROFT D. W. 
Published: July 2006

SummaryDetails of soil‐water profiles between drains and the associated drain‐flow data are presented for the winter period on a clay soil of the Ragdale series, formed in drift over Lias clay in the Midlands of England. A conventional water‐table is shown to exist and the rate of drain flow is shown to depend on whether the water‐table is high enough to be within layers having a better hydraulic conductivity than the normal subsoil. Mole drainage is shown to modify the drainage performance considerably by providing a quicker disposal of water, and significantly lower water‐table subject to much smaller fluctuations in level. Where drains have been laid in the natural subsoil, without this being disturbed by deep cultivations, the water‐table level is frequently close to cultivation level and there appears to be little water movement in the subsoil. It is concluded that for effective drainage, soils of this type require deep cultivations to modify the subsoil and allow water movement at greater depth.
A MODEL FOR PREDICTING THE REDISTRIBUTION OF SALTS APPLIED TO FALLOW SOILS AFTER EXCESS RAINFALL OR EVAPORATION
Authors: BURNS I. G. 
Published: July 2006

SummaryA model is described for predicting the movement of soluble unadsorbed anions (such as nitrate or chloride) in fallow freely drained soil under field conditions. The model includes routines for estimating both the downward leaching of salts (after excess rainfall or irrigation) and the capillary movement of anions to the soil surface (after evaporation). The profile is divided into layers each of which is characterized by a maximum and minimum water content (the field capacity and evaporation limit respectively). Daily amounts of rainfall and evaporation are applied to the surface and the redistribution of water and salts is calculated (on a layer‐to‐layer basis) from the initial water and salt contents of each layer by adding or subtracting water to or from the moisture content until the stated maximum or minimum value is reached. Salt transfer is calculated from the amount af water movement on a proportional basis. The predictions of the model have been tested using field data for the redistribution of nitrate and chloride in a sandy loam soil. Good agreement was obtained for chloride, but the results for nitrate showed some deviations probably due to the effects of denitrification.
FIXED AMMONIUM IN NIGERIAN SOILS I. SELECTION OF A METHOD AND AMOUNTS OF NATIVE FIXED AMMONIUM
Authors: OPUWARIBO E. , ODU C. T. I. 
Published: July 2006

SummaryThree of the common methods for the determination of native fixed ammonium in soils‐the Rodrigues modified, the Bremner KOH method, and the Silva Bremner method‐were evaluated and the Silva‐Bremner method was chosen. Native fixed ammonium in 212 profile samples representing different soil types and sampling localities in Nigeria was found to range from 4 to 98 ppm. Fixed ammonium accounted for 1‐7 per cent of total nitrogen in surface soils and 3‐48 per cent in the sub‐soils. More than half of the values fell within the ranges 2‐4 and 8‐20 per cent respectively. The results do not agree with the high values reported earlier for four Nigerian soil profiles.Fixed ammonium, both in absolute amounts and as a percentage of total nitrogen, increased with depth in most profiles though maximum amounts were not necessarily attained in the lowest horizons. Fixed ammonium values were lower in soils derived from sandy parent material than in those derived fromigneous or metamorphic rock and were generally less in the more humid southern parts of the country than in the drier north. Fixed ammonium, especially in subsoils, contributes to the nitrogen economy in these soils.
DISPLACEMENT OF AMMONIUM IONS FOR CATION EXCHANGE CAPACITY MEASUREMENTS
Authors: TUCKER B. M. 
Published: July 2006

SummaryThe best reagent for displacing adsorbed NH, for the measurement of cation exchange capacity of soils is a mixed ZN nitrate solution of potassium and calcium. The equivalent ratio of K to Ca should be in the range from 1 to 3. This mixture is better than simple solutions of Li, Na, K, Mg, Ca, Sr, and Ba nitrates and mixtures of KNO3 with any one or two of these other nitrates.
FORMATION OF IRON OXIDES BY DECOMPOSITION OF IRON‐PHENOLIC CHELATES
Authors: McHARDY W. J. , THOMSON A. P. , GOODMAN B. A. 
Published: July 2006

SummaryIron chelates of some simple di‐and trihydric phenols can be decomposed by peroxide treatment or by hydrolysis to yield crystalline ferric oxides. The species of ferric oxide obtained depends upon the precipitating conditions and the nature of the chelating ligand. In oxidative virtually anion‐free conditions, decomposition of all aged chelates yields a precipitate of disordered ferric oxide, which is referred to as‘protohaematite’, since it ages to haematite in water even at room temperature. Protohaematite is considered to be a discrete form of ferric oxide similar in structure to δ‐FeOOH but devoid of hydroxyl groups and may be present in freely drained soils as a precursor of haematite. Hydrolysis of all unaged chelates, except that of iron protocatechuic acid, yields lepidocrocite. The redox cycle undergone by iron in this reaction may be analogous to one prevailing in gley soils. In the presence of montmorillonite, the iron‐catechol system forms a clay‐metal‐organic complex, which also decomposes to yield lepidocrocite provided chloride ions are present on the clay surface. The fact that various inorganic gels amorphous to X‐rays can also deplete the ligand content of the chelates indicates a possible inorganic decomposition mechanism for metal‐organic chelates in soils.
DISSOLUTION KINETICS OF SILICATE MINERALS IN AQUEOUS CATECHOL SOLUTIONS
Authors: JØRGENSEN S. STORGAARD 
Published: July 2006

SummaryFine particle samples of silicate minerals and of gibbsite were shaken with solutions of pyrocatechol, 4‐nitro‐pyrocatechol or 3,4‐dihydroxybenzoic acid at pH 9·3–9·7 and 25°C. In 63 days, from 1·4 per cent (illite) to 17·9 per cent (nepheline) of the silica present was dissolved. Except for kaolinite in solutions of the two substituted catechols, the aluminosilicates dissolved incongruently, leaving residues enriched with aluminium.When accumulated amounts of elements (Si, Al, Na, K) dissolved from nepheline were plotted against time on log‐log paper straight lines were obtained. For quartz, kaolinite, and in some cases gibbsite similar plots could be approximated by two straight‐line segments. The plots for microcline and oligoclase may be described by a combination of three‐line segments. Several possible reaction mechanisms are discussed but a mechanism which explains the similar rate profiles has not yet been formulated.
CHEMICAL AND MINERALOGICAL PROPERTIES OF BROWN PODZOLIC SOILS IN COMPARISON WITH SOILS OF OTHER GROUPS
Authors: LOVELAND P. J. , BULLOCK P. 
Published: July 2006

SummaryChemical and mineralogical properties of brown podzolic soils, brown earths, a podzol, and an Andept have been studied with particular reference to the kinds and distribution of amorphous materials.In addition to pyrophosphate extractable (Fe + Al)/per cent clay, brown podzolic soils can be distinguished from brown earths by Fe‐oxalate/Fe‐dithionite and Fe‐pyrophosphate/Fe‐dithionite ratios, fluoride reactivity, and the presence of intergrade 2:1‐2:2 and smectite‐like clay minerals in surface horizons.Significant amounts of amorphous alumino‐silicates resembling allophane were found in the Bs horizons of the brown podzolic soils, particularly those on igneous rocks. These amounts are sufficiently large to suggest the recognition of an Andic sub‐group of brown podzolic soils in England and Wales.
ADSORPTION ON HYDROUS OXIDES. IV. MECHANISMS OF ADSORPTION OF VARIOUS IONS ON GOETHITE
Authors: PARFITT R. L. , RUSSELL J. D. 
Published: July 2006

SummaryInfrared spectroscopy has been used to investigate the complexes that are formed when acids are evaporated onto goethite. It is probable that, like HPO2−4, the anions SO2−4, SeO2−3, and oxalate are adsorbed by ligand exchange and form binuclear bridging complexes where two singly coordinated A‐type OH groups are replaced by two oxygen atoms of one ligand. There is evidence that HPO2−4 and oxalate are likely to be present in this form in wet environments, and this is probably also true for SO2−4 and SeO2−3.Fluoride ions can completely replace the singly coordinated A‐type OH groups but do not replace C‐ or B‐type OH groups that are coordinated, respectively, to two and three Fe3+ ions. The other halides, nitrate, and benzoate partially replace the A‐type OH groups, benzoate being adsorbed as a monodentate ligand.Copper ions do not appear to react with A‐type OH but zinc ions are probably adsorbed on the goethite (100) face in conjunction with carbonate or bicarbonate.
REACTIONS OF SOLUBLE PHOSPHATE WITH ACID SOILS: THE INTERPRETATION OF ADSORPTION‐DESORPTION ISOTHERMS
Authors: WHITE R. E. , TAYLOR A. W. 
Published: July 2006

SummaryAdsorption‐desorption and isotopic‐exchange isotherms for acids soils of known clay mineralogy indicated that when all the surfaœ P accessible to the solution was considered, the bonding energy for phosphate decreased exponentially with site coverage. The soils differed markedly in the quantities of surface P held at sites of very high bonding energy, defined as those in equilibrium with a solution concentration < 1 μM; the values ranging from 9 μmol g−1 in a soil with 40 per cent gibbsite in the clay fraction, to 1 μmol g−1 in a soil with only 1 per cent gibbsite and no interlayered material.The reversibility of current P adsorption on soil surfaces depended on the immediate history of the soil sample. Complete reversibility occurred when soil, previously enriched with soluble P and stored for 4 to 5 months at constant temperature, was suspended in solutions of constant pH and ionic strength. It is suggested that irreversibility occurs due to incomplete attainment of equilibrium during the adsorption phase, a condition predisposed by high initial P concentrations (>1mM), and the use of soils that are naturally in dis‐equilibrium because of recent fertilizer additions or severe depletion of P by plant uptake.
MEASUREMENT OF PORE SIZES IN FINE‐TEXTURED SOILS: A REVIEW OF EXISTING TECHNIQUES
Authors: LAWRENCE G. P. 
Published: July 2006

SummaryPore size distributions obtained from the relationship between moisture content and suction are not dependable in fine‐textured soils because of shrinkage. To overcome this problem, methods such as nitrogen sorption, mercury intrusion porosimetry, non‐polar liquid desorption and thin sectioning have been used. In order to pre‐dry samples without changes in the pore system, freeze‐drying, organic liquid replacement of soil water, and critical point drying techniques have been employed. These methods of soil drying and pore size measurement are described and compared, and the validity of their use in soil studies is examined. The measurement of pore sizes by water desorption is also discussed.