bluuebunny/crossref_metadata_2025_split huggingface dataset:
A basis for soil profile modelling in a geomorphic context
Authors: KIRKBY M. J. 
Published: July 2006

SUMMARYA mathematical model for soil profile evolution is developed in three parts; respectively for the weathering profile, the organic profile and for the inorganic profile associated with nutrient cycling. Processes modelled are percolation, equilibrium solution, leaching, ionic diffusion, organic mixing, leaf fall, organic decomposition and mechanical denudation. In each sub‐model some of these processes may be neglected, and time‐scales differ, so that they are best separated. Each leads to a second‐order linear partial differential equation with non‐constant coefficients. Equilibrium profiles are derived for the simplest cases, and numerical models exemplify profile evolution in more realistic cases. Modelled weathering profiles generally show a zone of near‐constant composition at the surface, with saprolite developing in deep profiles. Nutrient‐cycling profiles show the variable development of B‐horizons, and may be classified according to the relative depths of rooting, organic soil, and organic mixing processes.
Complementary use of thermal imagery and spectral analysis of soil properties and wheat yields to reveal cyclic patterns in the Flevopolders
Authors: BURROUGH P. A. , BREGT A. K. , de HEUS M. J. , KLOOSTERMAN E. G. 
Published: July 2006

SUMMARYThe Flevopolders in the north‐west of The Netherlands are located on recently reclaimed, uniform, flat alluvial soils. Strong contrasts in soil were thought to be unlikely. Yet thermal imagery of experimental fields carried out over 4 years revealed the presence of a striped pattern with a regular wavelength of 24 m. This was remarkable considering that drainage had been carried out at a 12 m spacing. Crop yields, topographic heights, tensiometer data, penetrometer readings and soil profiles also indicated the presence of a 24m ‘wave’. Investigations into the land reclamation procedures carried out 20 years ago finally revealed the cause. The implications for management are discussed.
A comparison between the diffusivity of gases in soil cores and in soil aggregates
Authors: PRITCHARD D.T. 
Published: July 2006

SUMMARYGas diffusivity was measured in duplicate soil cores (10 cm long and 6 cm diameter) from depths of 0–10, 10–20 and 20–30 cm, and in beds of 1–2 mm aggregates taken from the same site at the same depths. A steady state method was used, with ethane as the diffusing gas. As the samples dried, the fractional air‐filled pore space increased, from 0. 1 to 0.45 for the cores and from 0.35 to 0.65 for the aggregates. The maximum relative diffusivity of the aggregate samples (0.38) was approximately twice that of the core samples, reflecting the difference in pore space. Equations are presented for calculating the solid, air and water fractions of the samples and for calculating the diffusivity within peds and aggregates. These calculations allowed a comparison of the diffusion/porosity relationship within aggregates and peds.
The distribution of native and labelled carbon between soil particle size fractions isolated from long‐term incubation experiments
Authors: CHRISTENSEN B. T. , SØRENSEN L. H. 
Published: July 2006

SUMMARYFour soils with 6, 12, 23 and 46% clay were fractionated according to particle size after incubation for 5–6 years with 14C labelled straw, hemicellulose or glucose: 6–23% of the 14C was still present and the amount increased with increasing content of fine particles.clay fractions contained 66–84% of the 14C and the silt fractions accounted for 4–19%. <2% was found in the sand fractions and 4–9% was water soluble. The distribution of the native C was: clay, 46–68%; silt, 20–31%; sand, 2–7%.The clay fractions had higher relative proportions of 14C than of native C, the reverse being true for the silt fractions. This distribution pattern was not directly related to soil clay content or to kind of organic amendment.The C enrichment factor of clay and silt fractions (per cent C in fraction/per cent C in whole soil) increased with decreasing fraction size for both native and 14C. However, clay enrichment factors were higher for 14C than for native C, whereas silt enrichment factors were lower.A soil (9% clay) that had been incubated in the field for 18 years with 14C labelled straw was also analysed. Labelled C content at sampling was 9% of the initial value. In contrast to the other soils the distribution of labelled and native C was similar in the clay and silt fractions, which contained 55% and 33% of the whole soil C, respectively.The results indicate that clay‐bound organic matter may be important in mediumterm organic matter turnover, whereas silt‐bound organic matter may participate in longer‐term organic matter cycling.
The solubility of cations in soils
Authors: BENIANS G. 
Published: July 2006

SUMMARYWater‐soluble and exchangeable basic cations, and electrical conductivity, were measured in temperate and tropical soils. The ‘availability’ of cations in temperate soils is a function of both the amounts of exchangeable ions and the electrical conductivity of the solution, especially for divalent cations. In tropical soils the solubility of Ca and Mg seems less clear. The implications for some management problems are discussed.
Carbon/sesquioxide ratios in organic complexes and the transition albic‐spodic horizon
Authors: BUURMAN P. 
Published: July 2006

SUMMARYOrganic matter‐sesquioxide complexes in podzol B horizons are precipitated at specific carbon/sesquioxide ratios. Field data indicate that only part of the potential acidity is neutralized and that the maximum C/R2O2 ratio (minimum metal content) at which organic complexes will precipitate depends on pH of the soil and consequently on parent material and profile development. Although C/R2O3 ratios may be used regionally to predict the transition from soluble to precipitated complexes, such ratios cannot be used in soil classification or in a general definition of albic and spodic horizons.
Comparison of three field methods for measuring ammonia volatilization from urea granules broadcast on to pasture
Authors: BLACK A. S. , SHERLOCK R. R. , CAMERON K. C. , SMITH N. P. , GOH K. M. 
Published: July 2006

SUMMARYUrea granules were broadcast on to pasture (Lolium perenne/Trifolium repens) at a rate of 100 kg N ha−1. The evolution of NH3 from the soil was measured using three methods: an enclosure system with continuous air flow (EM), an unconfined micrometeorological method (integrated horizontal flux method—IHFM) and by measuring the recovery of N as urea, NH4+ and NO3− (NRM). The cumulative loss after 96 h measured by the three methods was 24%, 25% and 30% of the N applied respectively. After 144 h the daily rate of loss was small. At this time, EM and IHFM estimated the loss at 28%, while the NRM estimated a 45% loss. The higher estimated loss by the NRM was attributed mainly to microbial immobilization of applied N.Hourly fluxes estimated by the EM and the IHFM were very different. This was attributed to variations in the rate of urea hydrolysis which appeared to be more rapid in the confined EM system where the rate of soil drying was slower.
Annual losses of iron from moorland soils and their relation to free iron contents
Authors: GRIEVE IAN C. 
Published: July 2006

SUMMARYThe temporal pattern of iron loss from a moorland catchment was investigated by intensive stream water sampling. The total loss in 1 year was 2.11 kg ha−1 of Fe, with a pronounced autumn maximum. Iron concentrations in stream water were strongly correlated with dissolved organic matter content, but again with seasonal variation.Free iron content measured on a number of soils in the catchment ranged from 3.1 to 8.7 kg m−2. Assuming soil development over 10 000 years, predicted loss of iron from the catchment is comparable in quantity to the amounts of free iron in the soils.
The effect of oxidation by periodate on soil carbohydrate derived from plants and microorganisms
Authors: CHESHIRE M. V. , SPARLING G. P. , MUNDIE C. M. 
Published: July 2006

SUMMARYIt has previously been shown that treatment of soil with periodate and tetraborate releases much of the carbohydrate and destroys an equivalent proportion of the soil aggregates. The residual carbohydrate is proportionately richer in glucose, arabinose and xylose, sugars characteristic of plant remains, than the whole soil.The effect of sodium periodate (0.02 M, 6–168 h) and sodium tetraborate (0.1 M, 6 h) treatment of soil on carbohydrates of different origin was examined using 14C‐labelled soil in which the label was present in microbial products arising from 7 and 28 day incubations of 14C‐glucose in soil, or in both plant and microbial materials resulting from 12 week incubations of 14C‐labelled barley leaf and 1 year incubations of 14C‐labelled ryegrass in soil.Arabinose and xylose were the sugars most resistant to periodate in the glucose incubated soil; in the ryegrass incubation arabinose, xylose and glucose were more persistent than galactose, mannose and rhamnose. In the barley leaf incubation arabinose was more persistent than galactose and rhamnose. Thus periodate oxidation did not distinguish between sugars of different origin in soil and it was concluded that in the case of arabinose and xylose the persistence related to differences in chemical structures rather than to physical factors such as particle size of the plant fragments.The composition of the more stable residue can therefore not be used as an indication of polysaccharide origin in any comparison of the relative effects of plant and microbially derived material as aggregating agents.
Soil formation in the coast aeolianites and sands of Natal
Authors: MACVICAR C. N. , HUTSON J.L. , FITZPATRICK R. W. 
Published: July 2006

SUMMARYThe morphological, physical, chemical and mineralogical properties of eight prominent classes of soil developed in the coast aeolianites and sands of Natal are presented. These data and information on soil geography lead to the conclusion that: (i) losses of silica and bases and relative accumulation of iron (the ferrallitic process) have given rise to red and yellow kaolinitic materials; (ii) clay eluviation has given rise to coarse textured topsoils and to B2t horizons; and (iii) the hydromorphic process has caused grey colours in many sandy topsoils, plinthite development at some E/B horizon interfaces and gleying of some B2 horizons. In the soils on the older aeolianites, there is no evidence of either podzolization or the coarser textured topsoil being a younger geological deposit. The development of yellow soils in younger aeolianites may indicate a cooler climate than existed when red materials developed from the older aeolianites.
Incipient podzolization processes in Humic Acrisols of southern Spain
Authors: TORRENT J. , GOMEZ‐MARTIN F. 
Published: July 2006

SUMMARYSoils with morphological evidence of podzolization occur in Sierra Morena (southern Spain). Six soils, identified as Humic Acrisols, were sampled for detailed study. Distribution of oxalate‐ and EDTA‐extractable Al in Fe in the profiles indicated that substantial amounts of both elements had been translocated from the A to the incipient podzolic B horizons. Part of the Al, but almost no Fe, was present as organic complexes, suggesting that these two elements were transported to, or remobilized in the B horizons by different mechanisms. Allophane was present, albeit in small amounts, in two soils. Both inorganic and organic theories of podzolization were able to explain the Fe and Al distribution data.
The dissolution and dispersion of dicalcium phosphate dihydrate in soils.
Authors: KIRK G. J. D. , NYE P. H. 
Published: July 2006

SUMMARYThe model described in part I is tested against concentration profiles of calcium, phosphate and pH measured in thin sections of a soil block in contact with a dissolving layer of DCPD. The soil parameters required by the model are also measured, and the major assumptions of the model discussed in view of the findings. The close agreement between the predicted and experimental profiles shows that all important processes have been accounted for in the model. These would have to be included in models of the dissolution of granular DCPD in soil.
Topographic controls of soil moisture distributions
Authors: BURT T. P. , BUTCHER D. P. 
Published: July 2006

SUMMARYSoil moisture distributions on an instrumented hillslope at Slapton, South Devon, are compared to two topographic indices. The index a/s has been used in a computer runoff model to predict the location of zones of surface saturation on a hillslope (Beven & Kirkby, 1979), whilst the index plan curvature is derived from techniques of terrain analysis using gridded altitude data (Evans, 1980). Neither index is entirely satisfactory for predicting the changing pattern of soil moisture on the hillslope; a combined index proved most appropriate, but only at times of high soil wetness. The potential value of topographic indices as a basis for the prediction of soil moisture distributions and hillslope runoff is briefly discussed.
Effect of liming and air‐drying on the adsorption of phosphate by some acid soils
Authors: HAYNES R. J. , SWIFT R. S. 
Published: July 2006

SUMMARYThe effect of liming the A and B horizons of a number of acid soils on the subsequent adsorption of phosphate by soils retained moist or allowed to dry was investigated. Air‐drying increased the phosphate adsorption capacity but the reason was not clear.When A horizons were maintained moist, incubation with lime for six weeks increased phosphate adsorption by four samples and had no effect on another. When A horizons were air‐dried, the effect was considerably reduced or reversed. For B horizons, which had considerably greater phosphate adsorption capacities than A horizons, liming decreased phosphate adsorption irrespective of whether the soils remained moist or were dried. The relative decrease in adsorption was, however, greater when the soils were dried.In a more detailed study using one acid soil it was shown that incubation of the soil with lime for six weeks had no effect on phosphate adsorption by moist A and B horizons but after 36 weeks incubation liming decreased adsorption by the moist samples. If soils were dried then liming decreased phosphate adsorption after six or 36 weeks incubation. Such relative effects of liming on phosphate adsorption were confounded by the fact that air‐drying greatly increased the phosphate adsorption capacity of the unlimed soil. The drying effect was at least partially reversible following rewetting of the soil.Results were interpreted in terms of the lime‐induced increase in soil pH causing (i) the surface charge conferred on soil oxide surfaces to become more negative (thus decreasing phosphate adsorption) and (ii) the precipitation of exchangeable Al as hydroxy‐Al polymers resulting in the formation of new, highly active, adsorbing surfaces (thus increasing phosphate adsorption). Phosphate adsorption by moist limed soils can, therefore, be increased, decreased or unaffected depending on the relative magnitudes of these two processes. It is suggested that after liming, and/or air‐drying, crystallization of amorphous materials progressively decreases their surface area and adsorbing capacity. Thus, liming tends to decrease phosphate adsorption when the soils are dried.
Iron oxides in two Oxisols from the Brazilian coastal plain
Authors: FABRIS J. D. , RESENDE M. , DA SILVA E. GALVAO , COEY J. M. D. 
Published: July 2006

SUMMARYTwo Oxisols from the B2 horizon at similar locations 2 km apart on the Brazilian coastal plain with a udic, isohyperthermic regime were practically identical in chemical composition but differed markedly in colour; one was a dark reddish brown, the other a pale ochre. Mossbauer spectra at 295 K, 80 K and 4.2 K indicated a clear difference in iron oxide mineralogy. Iron was present as aluminous hematite and goethite, with Al substitutions of approximately 20% in the two phases. However, the relative proportion of iron present in hematite and goethite was 45:55 in the first sample and 12:88 in the second. Possible reasons for these differences are discussed.
A lysimeter study of the fate of nitrogen applied to perennial ryegrass swards: soil analyses and the final balance sheet
Authors: WEBSTER C. P. , DOWDELL R. J. 
Published: July 2006

SUMMARYLabelled fertilizer nitrogen was applied at a rate of 40 g N m−2 to grass swards growing in lysimeters containing monoliths of a sandy loam soil. After 5–7 years, during which time crop uptake and drainage losses of tracer nitrogen were measured, the soils were analysed to quantify the labelled nitrogen remaining. Approximately one‐third (range 31–35%) of the applied labelled nitrogen remained, with over 70% of this residue located in the top 20 cm of soil. The rate of mineralization of immobilized tracer nitrogen declined exponentially; after four years the release rate was almost constant, and was equivalent to 2% of the residual labelled nitrogen. Total labelled nitrogen measured in crop, drainage and soil amounted to 93–98%. That unaccounted for was presumed lost by denitrification, largely in the form of dinitrogen, as measured rates of nitrous oxide emission were negligible. The recovery was greatest (and by implication, the gaseous loss smallest) when fertilizer was applied in 1975 during a particularly warm and dry summer.
Compaction of a swelling clay soil by agricultural traffic; effects upon conditions for growth of winter cereals and evidence for some recovery of structure
Authors: BLACKWELL P. S. , WARD M. A. , LEFEVRE R. N. , COWAN D. J. 
Published: July 2006

SUMMARYA swelling stagnogley soil remained unwheeled or was uniformly wheeled by a combine harvester and a tractor in two successive autumns before direct drilling winter cereals. Combine wheeling of the soil at its wettest condition caused the largest loss of soil porosity.The autumn and spring of the second growing season for the winter cereals were wetter than long term average. The smaller porosity in the wheeled soil, created lower soil redox potential and smaller oxygen flux as well as greater soil strength and larger amounts of available water, but little difference in soil temperature. The crop in the wheeled soil had fewer plants, less root and a lighter yield than in the unwheeled soil.The wheeled soil recovered some porosity and lost strength after wetting and drying during the second growing season, whereas soil freezing had very little effect. This restructuring was sufficient to reverse some of the detrimental effects of compacting the soil.
A model of ammonia volatilization from applied urea. I. Development of the model
Authors: RACHHPAL‐SINGH  , NYE P. H. 
Published: July 2006

SUMMARYUrea application to soil raises the pH and ammonium concentration, thus providing ideal conditions for ammonia volatilization. A mechanistic model is presented, which combines the process of ammonia volatilization with the simultaneous transformation and movement of urea and its products in soil, for predicting the concentration profiles of urea, ammoniacal‐nitrogen and soil pH, and ammonia losses, following application of urea.The model consists of continuity equations describing the diffusion and reaction of urea, ammoniacal‐nitrogen and soil base; it takes into account the volatilization of ammonia and the concurrent acidification of the soil surface; and considers a variable PCo2 profile due to soil respiration and urea hydrolysis. The derivation of the continuity equations and their boundary conditions, calculations of ammonia volatilization, and appropriate methods for numerical solutions are described.
A model of ammonia volatilization from applied urea. II. Experimental testing
Authors: RACHHPAL‐SINGH  , NYE P. H. 
Published: July 2006

SUMMARYExperimental methods for the measurement of the transfer coefficient for ammonia volatilization from the soil surface to the atmosphere, the gaseous diffusion impedance factor in soil, and other parameters required by the predictive model are described. Following surface application of urea to soil columns, the measured concentration profiles of urea, ammoniacal‐nitrogen and soil pH, and the losses of ammonia by volatilization, were compared with the model predictions. The very good agreement between the measured and the predicted results suggested that all important processes have been accounted for in the model.
On the limitations of the simplified Elovich equation in describing the kinetics of phosphate sorption and release from soils
Authors: POLYZOPOULOS N. A. , KERAMIDAS V. Z. , PAVLATOU ATHENA 
Published: July 2006

SUMMARYThe kinetics of phosphate sorption and release from soils are often described by a simplified form of the Elovich equation. However, examination of data obtained with three soils from Greece as well as of published data, based on a modified version of the Elovich equation, showed that the assumptions underlying derivation of the simplified form are not valid in all cases. This modified version is free from any a priori assumptions, describes the kinetics of phosphate reactions with soils in a realistic manner and points out to the existence of more than one stage in the process.
Profile characteristics, and form and surface activity of inorganic phosphorus in a deep red Kenya coffee soil (Nitosol)
Authors: KETER J. K. A. , AHN PETER M. 
Published: July 2006

SUMMARYThe paper examines some of the physical and chemical properties of a deep red friable clay profile (Nitosol) developed in the Kenya highlands over trachyte. This soil is widely planted to coffee. The profile is remarkable for the depth and uniformity of the B horizon and for its stable microaggregation. Despite a clay content of 50–60% throughout the deep solum, the soil feels and handles like a loam.Work with radioactive phosphorus on samples from the profile and from nearby experimental plots under coffee showed that the activity, and the amounts, of surface phosphate fractions decreased in the order Fe‐P, Al‐P and Ca‐P, but the order of decrease of specific surface activity was Al‐P, Fe‐P, Ca‐P. The relative availabilities of these forms is discussed.
Cadmium accumulation in soils from long‐continued applications of superphosphate
Authors: ROTHBAUM H. P. , GOGUEL R. L. , JOHNSTON A. E. , MATTINGLY G. E. G. 
Published: July 2006

SUMMARYA simple, sensitive method developed for the analysis of geostandards was used to measure the accumulation of Cd in soils from superphosphate applied annually to grass‐land and arable soils for many years. Rates of application were equivalent to 33 kg P and 5 g Cd ha−1 yr−1 for 95 yr in three experiments in England and to 37 kg P and 20 g Cd ha−1 yr −1 for 30 yr in one experiment in New Zealand. Very little Cd accumulated in the surface horizons (0–22.5cm) of either of the arable soils from England; about one‐quarter of the applied Cd was detected in the sub‐soil (22.5–45.0 cm) of one experiment (Broadbalk) but none in the second (Barnfield). About one‐half of the applied Cd was retained in the 0–22.5 cm horizon of grassland soils from both England and New Zealand. The light (<2.2 gcm−3) organic‐rich fraction of Park Grass soil from Éngland contained about three times as much Cd as the heavier, mineral‐rich fraction. This suggests that when Cd is incorporated into organic matter its mobility is decreased and soil pH then has smaller effects on its mobility. Uptake of Cd by grass‐clover pasture in New Zealand averaged only 0.4 g Cd ha−1 yr−1 or 2% of the amount applied.