bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incorporation of natural alcohols from plant residues into hydromorphic forest‐podzol
Authors: JAMBU P. , AMBLÈS A. , JACQUESY J. C. , SECOUET B. , PARLANTI E. 
Published: July 2006

SUMMARYThe proportion of alcohols in soil lipids was studied in an hydromorphic forest‐podzol. The L and F litter layers and the soil A l horizon were sampled and analysed for total lipid and total alcohol contents. Total alcohols were separated into four fractions: primary alkanols, secondary alkanols, sterols and triterpenic alcohols.From the L layer to the soil A 1 horizon, all the fractions decreased sharply, except free primary alkanols and sterols. The decomposition of secondary alkanols was virtually complete. New odd‐chain primary alkanols were generated and new hopanoid alcohols (triterpenic alcohols), considered as markers of bacterial origin, were detected in the A 1 horizon. In the sterol fraction, the same components were observed in all the samples with changes concerning only their relative proportions.
Chemical characterization and decomposition of organic matter from two contrasting grassland soil profiles
Authors: HOPKINS D. W. , CHUDEK J. A. , SHIEL R. S. 
Published: July 2006

SUMMARYParticle size fractions of soils from the surface 6 cm of two adjacent grassland plots which, as a result of different fertilizer treatments since 1897, have either a mor or a mull humus form were analysed using solid‐state13C nuclear magnetic resonance spectroscopy and fractionation of organic N by steam distillation. In the mor humus soil, which had received 180 kg (NH4)2SO4ha−1annually and was pH 4.3, there was more C and N in the larger particle size fractions than in the mull humus soil (pH 5.8). The NMR spectra of correspondingly sized soil fractions were similar for both soils. The intensities of NMR signals between 0 and 40 ppm (alkyl‐C) and between 160 and 200 ppm (carbonyl‐C) increased with decreasing particle size. The intensities of the NMR signals between 60 and 90 ppm (0‐alkyl‐C) and between 90 and 110 ppm (acetal‐ and ketal‐C) decreased with increasing particle size. Comparison of the NMR spectra of the >2000 um fractions from both soils with those of dried grass litter from the same plots indicated the exclusive plant origin of the C in the largest size fraction of the soils. NMR resonances between 40 and 60 ppm were attributed to alkyl‐amino‐C because their intensities agreed with the amino‐N determinations obtained during organic N fractionation. During incubation in soil microcosms, the larger sized fractions decomposed more rapidly than the smaller fractions. However, all the correspondingly sized particle fractions from the two soils decomposed at the same rate except the >2000 pm fractions. The largest size fraction from the mor humus soil decomposed faster than that from the mull humus soil. This difference in decomposition rate could not be attributed to differences in the chemical composition of the >2000 pm fraction.
Composition of organic matter in particle‐size fractions of an agricultural soil
Authors: SCHULTEN H.‐R. , LEINWEBER P. , SORGE C. 
Published: July 2006

SUMMARYThe composition of organic matter was studied in clay (< 2 μm), fine silt (2‐6.3 μm), medium silt (6.3‐20 μm), coarse silt (20‐63 μm) and sand (63‐2000 μm) fractions of the Ap‐horizon of a clay loam (Orthic Humic Gleysol) from Bainsville (Ottawa, Canada) by organic C and total N analyses and pyrolysis‐field ionization mass spectrometry (Py‐FIMS).The C and N contents were largest in fine silt and medium silt and smaller in coarse silt and sand. Differences in the contents of organic matter and absorbed water were significantly (r= 0.945***) reflected by the amounts of volatilized matter during Py‐FIMS. The Py‐FI therniograms and mass spectra showed clear differences in thermal stability and molecular composition of organic matter between the organo‐mineral size‐fractions. Abundances of carbohydrates, phenols and lignin monomers, alkylaromatics and N‐containing compounds decreased, whereas abundances of lignin dimers and lipids increased with increasing equivalent diameters. An exception was the sand fraction which was dominated by the characteristic features of plant residues. The six compound classes, calculated using signals of biomarkers, accounted for 35% to 60% of the recorded total ion intensity.The thermal evolution of the selected compound classes, which are important constituents of soil organic matter (SOM), indicated the stability of humic and organo‐mineral bonds in particle‐size fractions, Moreover, the influence of mineral matrix on organic matter composition was shown by significant correlations between relative abundances of carbohydrates, N‐containing compounds, lipids, lignin dimers, and proportions of phyllosilicates.
The decomposition of straw in soil: use of Multiple Internal Reflectance Infrared Spectroscopy
Authors: CHESHIRE M. V. , RUSSELL J. D. , FRASER A. R. 
Published: July 2006

SUMMARYChanges in the surface layers of wheat and barley straw internodes incubated in soil at 15°C for up to 448 d were analysed using multiple internal reflectance (MIR) infrared spectroscopy. Results were compared with chemical analyses of total C and N and polysaccharides in straw and soil‐straw mixtures. Detectable spectroscopic changes occurred only at the inner surface of the straw. There was progressive enhancement of lignin absorption bands relative to those of polysaccharide and enhanced acetyl absorption. There was a greater association of clay mineral matter with the inner surfaces of the wheat straw than with those of the barley.Using the absorbance ratio of carbohydrate to lignin and assuming a negligible change in lignin content, it was estimated that for wheat straw about 75% of the carbohydrate in the surface layers was lost within the first 14 d of incubation. The barley straw showed no loss until 28 d, and 75% loss only after 112 d.In the early phases, the pattern of decomposition of straw carbohydrate in soil as revealed by MIR resembled that in sheep's rumen, but the rate of decomposition was much slower.Changes in the carbohydrate content of the soil‐straw mixtures measured chemically paralleled those observed spectroscopically, but only gross chemical changes were observable.MIR infrared spectroscopy was shown to provide a sensitive measure of the early stages of plant tissue decomposition.
Field‐measured redox potentials in soils at the groundwater–surface‐water interface
Authors: NORRSTRÖM A.C. 
Published: July 2006

SummaryAt the groundwater–surface‐water interface the last modification of discharging groundwater takes place. In this study the redox potential was measured in situ in four groundwater discharge areas with a size of 3–4 m2. Three of them were the upper reaches of streams in coniferous forests and one was an alder fen. Measurements were made at different seasons, with 50 and 100 platinum micro‐electrodes respectively, in each area. Readings were taken in the upper 30 cm of the soil, at two depths.A method study showed that the electrodes needed a longer equilibrium time than is usually reported. The main finding of this study was the large spatial variation within soils in the discharge zone; regions as small as 10 cm in diameter could have redox potentials covering several hundred mV. It was not possible to identify a seasonal variation due to the large spatial variation. Differences in the distribution of the redox potential with depth may be explained by the structure of the peat affecting flow patterns and the residence time of water.
Phosphate sorption by synthetic amorphous aluminium hydroxides: a 27Al and 31P solid‐state MAS NMR spectroscopy study
Authors: LOOKMAN R. , GROBET P. , MERCKX R. , VLASSAK K. 
Published: July 2006

SummaryThe sorption of phosphate on amorphous aluminium hydroxides was investigated using 27Al and 71P solid‐state magic‐angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, following the effect of different exposures to soluble phosphate. The spectra obtained were compared with the spectrum of amorphous aluminium phosphate. Aluminium in the unreacted hydroxide had a 100% octahedral co‐ordination. When dried at 200°C and exposed to soluble phosphate, very little (maximum 0.1%) amorphous aluminium hydroxide transformed to a tetrahedral co‐ordination (A1 bound by oxygen bridges to four P atoms), even after 120d. The tetrahedral co‐ordination exists in aluminium phosphate gel, although most of its A1 atoms exhibit an octahedral co‐ordination. For the aluminium hydroxide dried at 200°C, no formation of aluminium phosphate in which aluminium is in octahedral co‐ordination could be detected, not even when the aluminium hydroxide was exposed to a phosphate solution for 120 d. We concluded that the formation of aluminium phosphate is restricted to the surface of the hydroxide. Most of the phosphate which is bound to the aluminium oxide however may not have formed a ‘bulk solid’ aluminium phosphate, but is adsorbed on the internal and external surface of the oxide. The same amorphous aluminium hydroxide, dried at 70°C instead of 200°C, is converted much more rapidly to aluminium phosphate when exposed to soluble phosphate. We propose a P‐induced weathering mechanism to describe P sorption on amorphous aluminium hydroxides at high P concentrations. In addition to NMR, phosphate adsorption experiments conducted on aluminium hydroxides dried at different temperatures produced evidence that the porosity of the aluminium hydroxide aggregated particles can also be a factor controlling the rate of phosphate uptake from solution, if the aggregate is stable (is not resuspended) in solution.
Modelling soil distortion during compaction for cylindrical stress load paths
Authors: PETERSEN C. T. 
Published: July 2006

SummaryA slightly modified critical‐state model was formulated in order to account for the volume‐change behaviour at yield and failure observed in triaxial tests on unsaturated soils. Model parameters were specified for two soils (a sandy loam and a loam), each at three different soil‐moisture contents. Maximum shear strain was integrated numerically for 36 cylindrical load paths with constant confining pressure (type I) or constant mean normal stress (type II). Predicted stress‐strain relationships for load paths bringing soils from a normally‐consolidated to a critical state were compared with stress‐strain relationships observed for identical load paths in triaxial tests of the lubricated ends variety.The agreement between predicted and observed maximum shear strain depended on type of load path and soil‐moisture content. The model failed to predict maximum shear strain at stress states close to critical. The absolute difference between observed and predicted strain was on average ≤0.05 for deviatoric stresses smaller than 90% of the critical‐state values. The comparable maximum differences were 0.11 and 0.07 for load‐path types I and II, respectively. The largest differences were found for the largest soil‐moisture contents. The type of load path had a considerable effect on sample distortion, type I giving rise to larger (predicted and observed) maximum shear strain at common stress states.
Coregionalization of trace metals in the soil in the Swiss Jura
Authors: WEBSTER R. , ATTEIA O. , DUBOIS J.‐P. 
Published: July 2006

SummaryThe provenance of trace metals in soil, whether from the parent material or from pollution, is rarely known with certainty, and the metals' history must usually be pieced together from fragmentary statistical information. This is particularly true in the Swiss Jura where the concentrations of several heavy metals around La Chaux de Fonds exceed the statutory recommended thresholds for safety.The topsoil of the 14.5‐km2 region was sampled on a square grid at 250‐m intervals with additional nesting with distances of 100 m, 40 m, 16 m and 6 m. The concentrations of seven potentially toxic metals, namely Cd, Co, Cr, Cu, Ni, Pb and Zn, were measured. Their coregionalization could be represented by a linear model consisting of a nugget component plus two spherical structures with ranges of 0.2 km and 1.3 km. The short‐range component dominated the variograms of Cd, Cr, Cu and Pb; the long‐range component dominated those of Co and Ni; the variogram of Zn combined the two in approximately equal proportions. The coregionalization matrices contain moderate correlation among the nugget and the short‐range components, notably between Cu and Pb, between Cd and Zn, and between Cr, Ni and Zn. The strongest correlations are at the long range between Co, Cr and Ni, and to a somewhat smaller degree between Zn and Co. Analysis of variance showed Co and Ni to be related to geology, and to the Argovian formation in particular. The indicator variogram of this formation has also a short‐range component. The analysis also showed Cr and Cu to be related to land use (in different ways). Copper and Pb are strongly correlated to one another and distinct from the five other metals. The long‐range structure is almost certainly a geological effect, whereas the one of short range probably results from both the geology and human activities.
Simulating soil deformation using a critical‐state model: I. Laboratory tests
Authors: KIRBY J.M. 
Published: July 2006

SummaryThe paper examines the ability of a critical‐state model to predict stresses and deformations of agricultural soil in a variety of laboratory shear and compression tests. The critical‐state model used is a simple extension to the well‐known Modified Cam Clay model. The extension provides a smoother transition from elastic to plastic behaviour and, amongst other things, introduces a capacity to model cyclic loading. The model is incorporated into a finite‐element program.The model predictions are compared with: experimental observations of simple and direct shear tests with both constant normal stress and constant volume conditions; cyclic uniaxial compression tests; compaction tests in U‐shaped and V‐shaped boxes; and observations of some gross structural features caused by shear in direct‐shear boxes. Predictions are made for both the compressing, strain‐hardening and the expanding, strain‐softening regimes of behaviour. In all cases the material properties for the model were obtained from tests other than those being used for the comparisons.The model predictions generally compare well with the various experimental results, although some numerical problems were encountered in strain‐softening conditions. This demonstrates the versatility of the critical‐state model for predicting fairly general stress and, deformation conditions in unsaturated soils using only five material‐property constants. It also demonstrates that common laboratory strength and compression tests are adequate to measure the material properties.
Long‐term changes in chemical weathering rates between 1949–50 and 1987 in forest soils from north‐east Scotland
Authors: ZULLA Y. , BILLETT M.F. 
Published: July 2006

SummaryLong‐term changes in weathering rates in mineral soil horizons from the Alltcailleach Forest, north‐east Scotland, were estimated from a 3‐month leaching experiment conducted using archived soils sampled in 1949/50 and 1987. Data on changes in surface exchange chemistry, total element composition and mineralogy are also presented.The most sensitive Group 1 sites were characterized by a decrease in weathering rate and exchangeable Ca and Mg with time. Sodium increased in the total, exchangeable and the weatherable pools. The more base‐rich Group 2 sites exhibited a slight increase in weathering rate between 1949/50 and 1987.The results have implications for the use of weathering rates in the modelling of long‐term acidification of soils and water, and in the use of Na in weathering calculations as an element which is assumed not to accumulate in the soil‐plant system.
Diffusion from instantaneous sources of differing geometries
Authors: BIRD N.R.A. , DEXTER A.R. 
Published: July 2006

SummaryThe effects of geometry upon diffusion from instantaneous sources is considered. Although surface area is important initially, it is the square of the volume of the source which determines flux from the source at large times. This asymptotic shape independence is demonstrated for spherical and cuboidal sources.
EXPERIMENTS IN HAND‐WEEDING OF CONIFER SEEDBEDS IN FOREST NURSERIES
Authors: ALDHOUS J. R. 
Published: July 2006

Summary. In 3 years and in three nurseries, experimental plots sown with conifer seed were weeded by hand at intervals from 1½ to 12 weeks. Assessments of the seedlings at the end of each year showed a reduction in numbers and height only on plots left for 12 weeks between successive weedings. The total time taken to weed plots during the growing season was least for plots weeded at intervals of 3‐4 weeks and greatest for plots weeded at the longest intervals. Data on the total weight of weeds, the total number of weeds, the species composition and the stage of weed growth at weeding are also given and discussed.Essais de désherbage dans les pépinières
THE EFFECTS OF 4‐CHLOROPHENOXYACETIC ACID ON THE RHIZOME OF PTERIDIUM AQUILINUM (L.) KUHN
Authors: CONWAY E. , FORREST J. D. 
Published: July 2006

Summary. Tests have been carried out on the effects induced by the growth‐regulating compound 4‐chlorophenoxyacetic acid (4‐CPA) on the rhizome of Pteridium aquilinum when the compound is applied to the leaves of the plant. Experiments, made on unit plants grown from sporelings or fragments of mature rhizomes, and on stands of field bracken, showed that 4‐CPA in various formulations entered the tissues of the fronds easily and was readily translocated to the growing points of the rhizome branches. Epinasty, with hardening of the tissues of stem apices and frond buds, was seen after treatment with the chemical at low concentration; at higher concentrations, irregular growth led to splitting of the outer apical tissues and resultant rotting. Such harmful effects after treatment were seen to a high degree at the apices of stem branches bearing treated fronds. Lesser effects were seen on branches that were without expanded fronds at the time of treatment. In the field, time of application affected markedly the degree to which harmful effects were induced at the growing points. Spraying young fronds at herbicidal concentrations caused much scorching and early death, but the effects on the apices of the underground stem branches were relatively light. Spraying older fronds resulted in less obvious foliar effects, but damage caused to the rhizome was much greater. This may have been due to the young leaf tissues being killed before translocation had taken place. Surveys of untreated field bracken in the West of Scotland have shown that the matted underground stem contains a varying, mainly high, proportion of secondary branches with developing stem tips and frond buds not directly linked to an expanded frond, and that the frond population of a unit area docs not reflect the extent of the frond bud reserve. Since such secondary branches are those to which translocation appears to be restricted, they are likely to suffer only partial damage from chemical treatment of expanded fronds; and in the years following spraying, they may be expected to form frond populations relative to the extent of the frond bud reserve.Les effets de l'acide 4‐chlorophénoxyacétique sur le rhizome de Pteridium aquilinum (L.) Kuhn
FORMULATION OF DALAPON TO REDUCE SOIL CONTAMINATION
Authors: DAY BOYSIE E. 
Published: July 2006

Summary. Two means of reducing soil contamination resulting from the leaching of spray residues of dalapon from plant foliage were tested: use of volatile forms of the herbicide, residues of which slowly evaporate from the foliage; and use of formulations that congeal to a solid film to retain the herbicide against leaching. Rates of evaporation from glass slides at 20° C for the ethyl ester, n butyl ester, acid, and diethyleneglycol bisester of dalapon were respectively 15, 1‐6, 0′27 and 0.01 mg/cm2. As foliar herbicides the ethyl and butyl esters were ineffective and the acid of limited effectiveness due to rapid evaporation. The glycol ester was as effective as the sodium salt. With its evaporation rate of approximately 1 kg/ha/hr at 20°C, application of dalapon in the form of the diethylrneglycol bis ester is considered promising as a means of limiting soil contamination. Mixtures of the diethyleneglycol bis ester of dalapon with polyvinylacctate emulsion dry to form films that greatly reduce leaching of the herbicide at the expense of minor reduction in herbindal activity. Such formulations afford a means of limiting soil contamination.Formulation du dalapon pennettant de rédiuire la contamination du sol
EXPERIMENTS ON THE CONTROL OF WEEDS IN GROUNDNUTS IN TRIPOLITANIA
Authors: ORAM P. A. 
Published: July 2006

Summary. Studies on weed control in groundnuts grown with summer irrigation in the sandy coastal plain of Tripolitania (Libya) are described. These conditions favour rapid vigorous weed growth which competes severely with the crop; nearly 10 tons/ac of herbage was gathered from unweeded plots, on which groundnut yields were under half those from land kept effectively weeded. Early planting is desirable but may aggravate weed problems, due to inadequate time for cultivation and labour for weeding, through conflicting demands of other crops. It was therefore decided to investigate the possibilities of chemical control. Herbicides applied pre‐emergence included TCA, PCP, monuron, propham and 2,4‐D‐esters. Control of the predominant annual dicotyledons (Portulaca oleracea, Thlaspi arvense and Amaranthus retroflexus) comparable to that from hand‐weeding during early growth was obtained from PCP (10 lb/ac), the crop was not damaged by rates up to 20 lb. and the highest groundnut population was consistently established on plots treated with this herbicide. Effective control was obtained from 2,4‐D‐ester at 0.5 and 1.5 lb/ac, but the higher rate severely checked the groundnuts. Crop damage also occurred from monuron (3 lb/ac) which destroyed all vegetation, TCA (24 lb/ac) which was effective only against Cynodon dactylon; and propham (up to 10 lb/ac) which failed to control weeds. Post‐emergence treatment with MCPB (1.8 lb/ac) and 2,4‐DB (2.5 lb/ac) controlled some 50% of broad‐leaved weeds, but was slow to act and also damaged the crop. A combined PCP + 2,4‐D spray applied pre‐emergence proved to be the best chemical treatment, but maximum persistence was only about 10 weeks; after this, perennial monocotyledons such as C. dactylon and Cyperus sp., not effectively checked by any of the selective herbicides, became a serious problem. Under these conditions good yields depend on weed suppression late into the growing season and excellent results were achieved when an efficient pre‐emergence herbicide was followed, as its persistence waned, by careful handweeding. Early cultivation often damaged the crop, and a comparison of plots where this was omitted and the initial weeding delayed over several weeks, with those hand‐weeded throughout growth, showed no significant advantage from the extra operation. If no pre‐ernergence herbicides can be applied it may therefore be better to postpone the first cultivation for 5–7 weeks after planting. Observations on varieties representing the four broad morphological groups of groundnuts suggest certain differences in susceptibility to herbicides; further studies are required on this subject.Expériences sur le désherbage des Arachides en Tripolitaine