bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional analysis of soil organic matter as affected by long‐term manurial treatment
Authors: Ellerbrock R. H. , Höhn A. , Rogasik J. 
Published: March 2003

SummaryThe composition of soil organic matter (SOM) is influenced by land use and fertilization. We studied changes in the SOM in a long‐term field experiment on a sandy Podzoluvisol. The control plot and four combinations of manurial treatments of the experiment were selected: one with mineral fertilizer only and three combinations of organic manure with mineral fertilizer: cattle manure + NPK, cattle manure + PK and straw + NPK. The SOM was extracted by sodium pyrophosphate solution (pH = 10) and hot water (100°C). The extracts were analysed by Fourier‐Transform Infrared (FT‐IR) spectroscopy and gel permeation chromatography (GPC). The FT‐IR spectra from sodium pyrophosphate extracts indicate that composition of SOM is indeed influenced by different fertilization. The C=O band at 1710 cm–1 in the samples of the plots fertilized with cattle manure has the highest absorption intensity, whereas the material from the plot fertilized with straw + NPK has the least intense. The GPC analyses of the extracts showed that adding cattle manure + NPK increased the molecular size of SOM in comparison with the control plot. The analysis of hot‐water extracts with FT‐IR showed no significant differences in functional groups, but GPC chromatograms distinguished features in molecular size distribution. Fertilization with cattle manure increased the molecular size of the SOM in comparison with the control, but the differences in content of carboxylic groups and molecular weight were detected in sodium pyrophosphate extracts only.
Evaluation of an ultrasonic dispersion procedure to isolate primary organomineral complexes from soils
Authors: Schmidt M. W. I. , Rumpel C. , Kögel‐Knabner I. 
Published: March 2003

SummarySoil organic matter can be intimately associated with mineral particles of various sizes. For structural studies, soil organic matter can be isolated in particle size fractions after complete dispersion of the aggregates by ultrasonication. The ultrasonic dispersion energy necessary for complete dispersion was investigated in three A and two B horizons originating from four soils differing in pedogenesis (Gleysol, Phaeozem, Podzol, Alisol), organic C (4.2–34.5 g kg–1) and clay content (24–294 g kg–1). Calorimetric calibration of five probe‐type ultrasonifiers revealed that the actual energy output from an instrument can depart widely from its nominal output, and that this discrepancy varies from instrument to instrument. Calorimetric calibration is therefore essential for consistency and comparisons between laboratories. Between 450 and 500 J ml–1 of ultrasonic dispersion energy was enough to disperse completely all samples investigated. The particle size distributions obtained were close to those from standard analysis, except for smaller yields (–20 to –80 g kg–1) of sand size fractions, which suggests that dispersion by ultrasound is more effective. Based on total C, C:N ratio and distribution of dissolved C, no detachment of soil organic matter from primary organomineral complexes and no redistribution between particle size fractions could be detected in the range 30–590 J ml–1 of dispersion energy.
n‐Alkanes and free fatty acids in humus and A1 horizons of soils under beech, spruce and grass in the Massif‐Central (Mont‐Lozère), France
Authors: Marseille F. , Disnar J. R. , Guillet B. , Noack Y. 
Published: March 2003

SummarySoil profiles under beech, spruce and a grassland have been analysed to study the evolution of natural n‐alkanes in pollution‐free ecosystems. The soils had all developed on granitic bedrock, at an altitude of 1300–1500 m in the region of Mont‐Lozère (southern Massif‐Central, France). In contrast to the grassland soil, the two forest soils both possessed a well‐developed acidic moder humus‐type horizon. This could be subdivided as follows: fresh litter (OL), fragmentation (OF) and humification (OH) layers; two litters, one fresh (OL1) and one old (OL2) could actually be distinguished in the beech forest soil. The n‐alkane signature of the parent plants was preserved in the top litter. Immediately underneath, in the OF layer(s) the original n‐alkane signatures were progressively but rapidly replaced by a common signature composed of n‐C27 and n‐C25 with larger proportions of the former than of the latter. These two hydrocarbons were most probably produced in situ by fungi. These results appear to illustrate the action of soil microorganisms which metabolize the inherited n‐alkanes and produce new compounds of the same family. Unlike the alkanes and the low molecular weight fatty acids ≤ C20 (which increase greatly in the OL2 layer under beech as a result of intense microbial activity), the heavy fatty acids (> C20) show no significant change in the organic horizon.
Sorption of atrazine, 2,4‐D, nitrobenzene and pentachlorophenol by urban and industrial wastes
Authors: Wu Q. , Blume H. ‐P. , Rexilius L. , Fölschow M. , Schleuss U. 
Published: March 2003

SummaryThis study was carried out to investigate the sorption properties of man‐made soil developed from sewage sludge, municipal wastes, brick and mortar debris, harbour sludge, sand fills, fly ash, and wastes from coking plants and coal mines. The composition of organic matter in the samples was analysed, and the sorption isotherms of four reference chemicals (nitrobenzene, atrazine, 2,4‐D, pentachlorophenol) were determined. Fly ash, which contains up to 89% of its carbon as Black Carbon, showed a strong affinity to all four chemicals. For the other waste materials, a strong correlation between the logarithm of the Freundlich adsorption constant, Kf, and the logarithm of organic carbon, Co, was established (r = 0.85–0.96). This holds for the non‐ionic nitrobenzene and also, within a certain pH range depending on the pKa of the compound, for the three ionizable organic compounds (atrazine: pH > 4; 2,4‐D: pH > 5; PCP: pH > 6). At pH near the pKa value the sorption is sensitive to pH. There were no statistically significant differences between the waste materials and the natural soils in the relations between logKf and logCo for either ionic or non‐ionic chemicals. This result suggests that the method devised for estimating the sorption of organic chemicals in natural soils based on their content of organic carbon is equally valuable for the waste materials, with the exception of fly ash which contains a large amount of Black Carbon.
Changes in organic matter, nitrogen, phosphorus and cations in soil as a result of fire and water erosion in a Mediterranean landscape
Authors: Gimeno‐García E. , Andreu V. , Rubio J. L. 
Published: March 2003

SummaryFire affects large parts of the dry Mediterranean shrubland, resulting in erosion and losses of plant nutrients. We have attempted to measure these effects experimentally on a calcareous hillside representative of such shrubland. Experimental fires were made on plots (4 m × 20 m) in which the fuel was controlled to obtain two different fire intensities giving means of soil surface temperature of 439°C and 232°C with temperatures exceeding 100°C lasting for 36 min and 17 min. The immediate and subsequent changes induced by fire on the soil's organic matter content and other soil chemical properties were evaluated, together with the impact of water erosion.Seven erosive rain events, which occurred after the experimental fires (from August 1995 to December 1996), were selected, and on them runoff and sediment produced from each plot were measured. The sediments collected were weighed and analysed. Taking into account the variations induced by fire on the soil properties and their losses by water erosion, estimates of the net inputs and outputs of the soil system were made. Results show that the greatest losses of both soil and nutrients took place in the 4 months immediately after the fire. Plots affected by the most intense fire showed greater losses of soil (4077 kg ha−1) than those with moderate fire intensity (3280 kg ha−1). The unburned plots produced the least sediment (72.8 kg ha−1). Organic matter and nutrient losses by water erosion were related to the degree of fire intensity. However, the largest losses of N‐NH4+ and N‐NO3– by water erosion corresponded to the moderate fire (8.1 and 7.5 mg N m−2, respectively).
Modelling the solid–solution partitioning of organic matter in European forest soils
Authors: Lofts S. , Simon B. M. , Tipping E. , Woof C. 
Published: March 2003

SummaryThe processes controlling the solid–solution partitioning of organic matter in soils are central to understanding carbon cycling in terrestrial ecosystems, yet are poorly understood at present. We studied the partitioning of soil organic matter between solid and solution in batch titrations of 12 soil samples from three European forests in a range of climates. We also examined the release of soil organic matter on repeated leaching. The partitioning was simulated using a model that pictures the pool of potentially mobile organic matter to consist of fractions of differing solubilities. Desorption of organic matter was then effected by an increase in the electrical charge of the organic molecules due to their chemical reactions with other soil components.The model could simulate the partitioning of organic matter in all the soils using two parameters describing the amounts of soil organic matter in each fraction. The release of organic matter on repeated leaching was reasonably well described. The model predicted that dissolved organic matter should have become more hydrophilic with depth in the soil, due to the retention of more hydrophobic components in the upper horizons. This accorded with observed compositions of the soil organic matter. The model also showed that at the ambient pH of the soils, only a small proportion of the potentially mobile organic matter (comprising fulvic acids and hydrophilic moieties) was involved in partitioning to the solution.
A new sampling technique to monitor concentrations of CH4, N2O and CO2 in air at well‐defined depths in soils with varied water potential
Authors: Kammann C. , Grünhage L. , Jäger H. ‐J. 
Published: March 2003

SummaryA new sampling technique for measuring the concentrations of trace gases (CH4, CO2 and N2O) in the soil atmosphere from well‐defined depths is described. Probes are constructed from silicone tubing closed with silicone septa on both ends, thereby dividing an inner air space from the outer soil atmosphere without a direct contact. The gas exchanges between the inner and outer atmosphere only by diffusion through the walls of the silicone tube. Tests revealed that the gases N2O, CO2 and CH4 in the enclosed space reached 95% equilibrium with the surrounding atmosphere at 20°C within 7 h or faster. The probe measurements are reproducible: the standard deviation of samples taken from 26 probes stored in the laboratory atmosphere equalled that of a standard gas. The probes can easily be constructed and installed at specified depths in the soil.The method has the following advantages compared with other methods that use spaces with holes in them for gas exchange: (i) the silicone probe enables trace gases to be sampled in wet soils, including ones that are waterlogged or temporarily saturated; (ii) the sampling itself does not create low pressure and hence does not create mass flow in the soil matrix from undefined depths; and (iii) the probe can be made to take samples of gas of any required size. The silicone probes did not show ageing effects during 18 months of use in the field in a mineral soil under grass. The probes yielded comparable results: three probes inserted at 5 cm depth in a uniformly treated 100‐m2 plot provided nearly identical average trace gas concentrations within the measurement period.
Influence of soil strength on root growth: experiments and analysis using a critical‐state model
Authors: Kirby J.M. , Bengough A.G. 
Published: March 2003

SummaryRoots grow thicker in compacted soil, even though it requires greater force for a large object to penetrate soil than it does for a small one. We examined the advantage of thickening in terms of the stresses around a root penetrating with constant shape, rather than the stresses around an expanding cylinder or sphere, as has been studied previously. We combined experiments and simulations of the stresses around roots growing in compacted soils. We measured the diameter of pea roots growing in sandy loam and clay loam at four different densities, and the critical‐state properties of the soils. At a penetration resistance of about 1 MPa the diameter of the roots in the sandy loam was about 40% greater than that at 0.7 MPa, and at 2 MPa it was about 60% greater. In the clay loam, there was less thickening – about 10% greater at 1 MPa and about 20% greater at 1.5 MPa. The maximum axial stresses were predicted using a critical‐state finite‐element model to be at the very tip of the root cap. When there was friction between the root and the soil, shear stresses were predicted with smaller values at the tip than just behind the tip. When the interface between the soil and the root was assumed to be frictionless, there were by definition no shear stresses. In the frictionless case the advantage of root thickening on relieving peak stress at the root tip was diminished. The axial and shear stresses were predicted to be smaller in the clay loam than in the sandy loam and may explain why the roots did not thicken in this soil although its resistance to penetration was similar. Our results suggest that the local values of axial and shear stresses experienced by the root near its tip may be as important in constraining root growth as the total penetration resistance.
Pollution of carbonate soils in a Mediterranean climate due to a tailings spill
Authors: Simón M. , Dorronsoro C. , Ortiz I. , Martín F. , Aguilar J. 
Published: March 2003

SummaryThe retention walls in a pond containing the residues from the pyrite mine of Aznalcóllar (southern Spain) broke open on 25 April 1998, spilling approximately 6 × 106 m3 of polluted water and toxic tailings, which affected some 55 km2. Drying and aeration of the tailings resulted in oxidation, forming an acidic solution with high pollutant contents, the effects of which were studied in a calcareous soil. The infiltration of this solution markedly affected only the first 12 mm of the soil, where strong acidification caused the weathering of the carbonates, and where the fine mineral particles were hydrolysed. The SO42− ions in the acidic solution precipitated almost entirely at this depth, forming gypsum, hydroxysulphates and complex sulphates. The Fe3+ ions also precipitated there, mainly in amorphous or poorly crystallized forms, adsorbing to As, Sb, Tl and Pb dissolved in the acidic solution. The Al3+ ions, though partly precipitating in the acidic layer, accumulated mostly where the soil pH exceeded 5.5 (12–14 mm in depth). They did so primarily as amorphous or poorly crystallized forms, adsorbing to Cu dissolved in the acidic solution. The Zn2+ and Cd2+ ions accumulated mainly at pH > 7.0 (19–21 mm in depth), being adsorbed chiefly by clay mineral. After 15 months, only the first 20 mm of the soil were acidified by the oxidation of the tailings and most of the pollutants did not penetrate deeper than 100 mm. Consequently, the speed of the cleanup of the toxic spill is not as important as a thorough removal of tailings together with the upper 10 cm of the soil.
Modelling soil pore characteristics from measurements of air exchange: the long‐term effects of fertilization and crop rotation
Authors: Schjønning P. , Munkholm L. J. , Moldrup P. , Jacobsen O. H. 
Published: March 2003

SummaryLong‐term cultivation of soils for arable crops and without application of organic manure is thought to reduce the soil quality for crop production. We studied the porosity of two sandy loam soils from organic dairy farms with a ley cropping system and compared them with a conventionally managed dairy farm growing arable crops only and an arable soil receiving only mineral fertilizers, respectively. Saturated hydraulic conductivity, water retention characteristics, air diffusivity and air permeability were determined in the plough layer of the soil.The soil of one of the organic dairy farms contained many more earthworm burrows and had a significantly larger hydraulic conductivity than the counterpart soil of the conventionally managed dairy farm. In other respects, these two soils were much alike. The soil of the other organically managed dairy farm was less dense and had a larger volume of pores > 30 μm than the arable soil receiving only mineral fertilizers. A tube model was used to combine the air exchange measurements in a description of the soil pores. The pore system of the mineral fertilized soil consisted of continuous arterial pores with only a small volume of blocked and marginal pores embedded in the soil matrix next to the arterial pores. The porosity of the counterpart organic dairy farm soil had a considerable volume of blocked and especially marginal pores. The complexity of the latter was considered beneficial for local aeration in the soil and for derived soil properties such as fragmentation on tillage.
Uncertainty analysis for pedotransfer functions
Authors: Minasny B. , Mc Bratney A. B. 
Published: March 2003

SummaryBoth empirical and process‐simulation models are useful in predicting the outcome of agricultural management on soil quality and vice versa, and pedotransfer functions have been developed to translate readily available soil information into variables that are needed in the models. The input data are subject to error, and consequently the transfer functions can produce varied outputs. A general approach to quantifying the resulting uncertainty is to use Monte Carlo methods. By sampling repeatedly from the assumed probability distributions of the input variables and evaluating the response of the model, the statistical distribution of the outputs can be estimated. Methods for sampling the probability distribution include simple random sampling, the sectioning method, and Latin hypercube sampling. The Latin hypercube sampling is applied to the quantification of uncertainties in pedotransfer functions of soil strength and soil hydraulic properties. Hydraulic properties predicted using recently developed pedotransfer functions are also used in a model to analyse the uncertainties in the prediction of soil‐water regimes in the field. The uncertainties of hydraulic properties in soil‐water simulation show that the model is sensitive to the soil's moisture state.
Increases in pH and soluble salts influence the effect that additions of organic residues have on concentrations of exchangeable and soil solution aluminium
Authors: Mokolobate M. S. , Haynes R. J. 
Published: March 2003

SummaryIt has been suggested that additions of organic residues to acid soils can ameliorate Al toxicity. For this reason the effects of additions of four organic residues to an acid soil on pH and exchangeable and soil solution Al were investigated. The residues were grass, household compost, filter cake (a waste product from sugar mills) and poultry manure, and they were added at rates equivalent to 10 and 20 t ha−1. Additions of residues increased soil pH measured in KCl (pH(KCl)) and decreased exchangeable Al3+ in the order poultry manure > filter cake > household compost > grass. The mechanism responsible for the increase in pH differed for the different residues. Poultry manure treatment resulted in lower soil pH measured in water (pH(water)) and larger concentrations of total (AlT) and monomeric (Almono) Al in soil solution than did filter cake. This was attributed to a soluble salt effect, originating from the large cation content of poultry manure, displacing exchangeable Al3+ and H+ back into soil solution. The considerably larger concentrations of soluble C in soil solution originating from the poultry manure may also have maintained greater concentrations of Al in soluble complexed form. There was a significant negative correlation (r = −0.94) between pH(KCl) and exchangeable Al. Concentrations of AlT and Almono in soil solution were not closely related with pH or exchangeable Al. The results suggest that although additions of organic residues can increase soil pH and decrease Al solubility, increases in soluble salt and soluble C concentrations in soil solution can substantially modify these effects.
Predicting carbon content in illitic clay fractions from surface area, cation exchange capacity and dithionite‐extractable iron
Authors: Kahle M. , Kleber M. , Jahn R. 
Published: March 2003

SummaryWe used the specific surface area (SSA), the cation exchange capacity (CEC) and the content of dithionite‐extractable iron (Fed) to predict the content of organic carbon in illitic clay fractions of topsoils from loess. We determined SSA (BET‐N2 method) and CEC of clay fractions after removing organic C or reducing oxides or both. The CEC and the SSA of the carbon‐ and oxide‐free clay fraction explained 56% and 54% of the variation in C content, respectively. The Fed content of the clay fractions was strongly and negatively related to the C content, and with the SSA of the carbon‐free clay fraction it predicted C content almost completely (R2 = 0.96). The results indicate that the amount of cations adhering to the silicate clay minerals and the size of the silicate mineral surface area are important properties of the mineral phase for the storage potential of C. The reason for the negative relation between iron oxides and C content remains unclear.
Phosphorus uptake by rice from soil that is flooded, drained or flooded then drained
Authors: Huguenin‐Elie O. , Kirk G. J.D. , Frossard E. 
Published: March 2003

SummaryTo investigate the mechanisms by which rice plants growing in alternately flooded and drained soils absorb soil phosphate, we grew rice in moist, flooded and flooded then moist soils, and compared the measured uptake of phosphorus (P) with that calculated using a mathematical model of uptake allowing for solubilization by various means. The theory and equations for the model are given, together with a method for solving diffusion equations near roots in a root system of increasing density. The diffusion coefficients and buffer powers of P in the soil under the different water regimes are measured by following diffusion of P to a resin sink, and the parameters describing solubilization are estimated from previously published results. In all the water regimes studied, the plants relied upon solubilization for most of their P. The roots were not mycorrhizal, as they will often not be in intermittently flooded soils. In the flooded soil, uptake was three times that in the moist soil, and was consistent with solubilization by acidification caused by roots as a result of oxidation of iron and imbalance between the intake of cations and anions. In the moist soil, the uptake was consistent with solubilization by excretion of organic anions from the roots. In the flooded then moist soil, uptake declined sharply as the soil dried because P became immobilized in the soil. However, the final uptake was similar to that in the continuously moist soil, indicating that some of the immobilized P was re‐solubilized by roots, possibly by excretion of organic anions.