bluuebunny/crossref_metadata_2025_split huggingface dataset:
The solidsolution equilibria of lead and cadmium in polluted soils
Authors: JOPONY M. , YOUNG S.D. 
Published: July 2006

SummaryA method for the measurement of Pb and Cd in equilibrium soil solutions involving soil equilibration with a dilute Ca electrolyte, centrifugation and filtration to <0.2 μm was evaluated. The procedure was subsequently used for the analysis of 100 Pb‐ and 30 Cd‐contaminated soils. Solutions were analysed for Pb‐ and Cd using graphite‐furnace AAS and the concentrations of Pb2+ and Cd2+ were estimated using standard speciation calculations.The concentrations of Pb and Cd found in the soil solutions were in the range 3.5–3600 μg dmp −3 and 2.7–1278 μg dm −3 respectively; both ranges represented less than 0.1% of the total metal concentration in the soils. Depending on solution pH, Pb +2 accounted for between 42–78% of Pb in solution while about 65% of Cd in solution was present as Cd+2. The concentrations of Pb2+ and Cd2+ in solution suggested that the soil solutions were undersaturated with respect to the solid phases PbC03 and CdC03 but supersaturated with respect to Pb5(P04)3Cl and, for some samples, Cd3(P04)2 respectively. However, for both metals, a good empirical relationship was obtained between the total metal concentration in soil (mol kg−1), free metal concentration in solution (mol dm−3) and solution pH. The relationships took the general form of a pH‐dependent Freundlich adsorption equation:

image

For both lead and cadmium relationships, the values ofn and K1 were close to unity, so that the distribution coefficient could be estimated from pH and a single metal‐dependent constant, K2. The algorithms appeared to be valid over a metal concentration range of four logarithmic units and pH range of 3.5–7.5.
Retention of heavy metals by soils in the presence of a residue from the olive‐oil industry
Authors: MADRID L. , DÍAZ‐BARRIENTOS E. 
Published: July 2006

SummaryThe effect of the presence of alpechín, wastewater from the olive‐oil industry, on the reaction of three soils with Cd, Cu and Zn is studied. Adsorption of Cu and Zn by all the soils studied, and Cd by one of the soils, is markedly decreased by the presence of high doses of alpechín, while Cd adsorption by the other two soils increases in the presence of the residue. Adsorption of Cu and Zn in the absence of alpechín releases considerably more Ca than the exchangeable contents at a rate of about 0.5‐1 moles of Ca for each mole of metal adsorbed, and this rate is decreased in most cases when alpechín is present. The behaviour of Cd with respect to Ca release is less definite. The relationships between solution concentrations and pH show that alpechín increases the mobility of Cd and Cu in the presence of some soils, while in the case of Zn no effect is evident.It is concluded that soil carbonate is the most relevant component involved in Cu or Zn retention, and, in the presence of alpechín, part of the carbonate surface is blocked and becomes unavailable for retention. Formation of soluble Cu complexes is suggested to occur in some cases.
A functional model of soil porosity used to interpret measurements of gas diffusion
Authors: ARAH J.R.M. , BALL B.C. 
Published: July 2006

SummaryA simple model was employed to interpret the results of a series of measurements of gas diffusion in soil cores. The model divides air‐filled porosity into three functional categories: arterial, marginal and remote. Diffusion along the axis of the core occurs through arterial pores; marginal pores do not contribute to axial diffusion; remote pores are isolated from gas transport. Simulations based on the model closely resembled data acquired from real cores. Optimizing the fit between real and simulated data gave estimates of the three functional pore fractions which generally made sense (compaction or wetting of cores resulted in reduced arterial and increased marginal porosities, for example). Dividing the pores into the different classes specified by the model was functionally equivalent (i.e. observable results were identical) to the introduction of a tortuosity factor to represent pore convolution. In order to account for observed diffusion rates in terms of pore convolution alone it is sometimes necessary to invoke implausibly high tortuosities; the introduction of marginal porosity renders this unnecessary without in any way compromising the ability of the model to simulate real diffusion data.
Propagation of the error of spatial prediction of soil properties in simulating crop evapotranspiration
Authors: LEENHARDT D. , VOLTZ M. , BORNAND M. 
Published: July 2006

SummaryA major problem in using soil‐water models for land evaluation is to define which combination of model complexity and sampling density provides the most reliable predictions for a given investment. The overall error which affects the predictions arises from different sources. For instance, one is the error due to spatial estimation of soil data from soil classifications. The paper describes, for two models of different complexity and two soil maps of different resolution, how this error is propagated to the predictions of crop evapotranspiration.Errors arose and were accumulated during the course of the simulations, but they were not amplified. The variance of the errors depended on the climatic conditions of the simulations. Nevertheless, whatever the conditions, uncertainties in soil properties were propagated to the predictions to a lesser extent by the simple model than by the complex one. For example, combining the simple model and the 1/10 000 map required the same experimental investment as combining the complex model and the 1/100 000 map, but the variance of propagated errors was 53% greater for the complex model than for the simple one. Thus, if we consider only the simulation error derived from estimation errors in soil properties and the sampling costs, it is justifiable to use simple models for predicting the soil water balance in space. However, decisions should be based on the overall precision of the simulations which is also affected by other sources of error, such as the error arising from the model itself.
Influence of soil properties on the response to phosphorus in some tropical soils: II. Response to fertilizer P residues
Authors: WARREN G.P. 
Published: July 2006

SummaryThe residual values of fertilizer P in six tropical soils were assessed from the response of grass in a pot experiment. The comparison was made between residues of P that had been applied to a previous crop (also grass) and fresh P applied to uncropped soil. Yields of dry matter and P uptakes were fitted to Mitscherlich and linear equations respectively, and the availabilities of fresh and residual P were assessed by fitted parameters of these equations.With sufficient residual P, the maximum yields were close to those obtained with fresh P, but residual P always had a lower availability than fresh P. The residual value was assessed by the ratio of the availability parameters for residual and fresh P and these values showed that there were differences between soils in the decline of P availability. Residual value was not directly related to the initial availability of P.The P uptake responses to both fresh and residual P were correlated significantly with buffer capacity for exchangeable sorption of phosphate and Al extracted by acid oxalate. This suggested that there is an available fraction of residual P, the uptake of which is influenced by the sorption and mobility of phosphate in soil, in the same way as for fresh fertilizer P.
The contribution from hyphae, roots and organic carbon constituents to the aggregation of a sandy loam under long‐term clover‐based and grass pastures
Authors: DEGENS B.P. , SPARLING G.P. , ABBOTT L.K. 
Published: July 2006

SummaryWater‐stable macro‐aggregate size fractions (>2.0 mm, 1.0–2.0 mm, 0.5–1.0 mm and 0.25–0.5 mm) and non‐aggregated soil from a sandy loam under long‐term clover‐based pasture and from grass pasture were analysed to determine the role of acid‐ and water‐extractable carbohydrate C, total hyphal length, microbial biomass, organic C and total and mycorrhizal root length in stabilization of the aggregates. Aggregates were examined by scanning electron microscopy (SEM) and the particle‐size distribution of the size fractions was also determined.Macro‐aggregation increased under grass, relative to clover‐based pasture; however, the properties of the aggregate fractions measured did not reflect this difference. Microbial‐biomass C, extractable‐carbohydrate C, hyphal length, total and mycorrhizal root length and organic C content of the soils were poorly correlated with macro‐aggregation. Within the aggregates, the proportion of 250–1000‐km sand was smaller and clay, silt and fine sand (20–250 μm) were greater relative to non‐aggregated soil, suggesting that the >250‐μm sand in the non‐aggregated soil limited the stabilization of macro‐aggregates. Under SEM, no enmeshment of aggregates by hyphae and roots was apparent. Although 50–160 m hyphae g−1 soil was found within the aggregates, calculations showed that on average only 5 to 13 lengths of hyphae were associated with each 250‐μm cube of soil within the aggregates, and suggested little potential to stabilize the aggregates by enmeshing. On average, all >2.0‐mm aggregates contained less than 3.6 mm of roots and less than 50% by weight of <2.0‐mm aggregates contained a single length of root. The findings cast doubt about the role of hyphae and fine roots in the stabilization of macro‐aggregates through an enmeshing mechanism in sandy soils.
EXPERIMENTAL STUDIES OF THE MORTALITY AND PLASTICITY OF A WEED
Authors: HARPER JOHN L. , GAJIC DANICA 
Published: July 2006

Summary. An attempt is made to show the ways in which a population of annual plants may react to increasing density so that the population becomes self‐regulatory. The reactions of Agrostemma githago to increasing density lake the form of increasing mortality and plastic response in the size and reproductive capacity of individuals. Experiments are described in which both of these reactions occur and it is shown that interference between Agrostemma and other species may influence either or both reactions. The significance of these observations for understanding the mechanism of natural selection is stressed.Etude expérimentale de la mortalité et de la plasticité d'une mauvaise herbe
THE FATE OF N'‐(4‐CHLOROPHENOXY)‐PHENYL‐NN‐DIMETHYLUREA (C‐1983) IN SOILS AND PLANTS*
Authors: GEISSBÜHLER H. , HASELBACH C. , AEBI H. , EBNER L. 
Published: July 2006

Summary. The pathway and the rate of breakdown of C‐1983 in bacterial suspensions, soil samples and plants was investigated with the 14C‐carbonyl‐labelled herbicide.Bacterial suspensions derived from humus soil were demonstrated to metabolize C‐1983 [I] to N'‐(4‐chloropheuoxy)‐phenyl‐N'‐methylurea [II], N'‐(4‐chlorophenoxy)‐phenylurea [III] and (4‐chlorophenoxy)‐aniline [V]. In addition, at least two minor, unidentified metabolites were observed.In samples of humus soil and sandy loam, the pathway of degradation was found to be essentially the same as in bacterial suspensions. The rate of breakdown was slightly higher in sandy loam (35% loss in 8 weeks) than in humus soil (25% loss) under optimal growth conditions (temperature, humidity). In humus soil, which is highly adsorptive for C‐1983, breakdown decreased with time, thereby suggesting that desorption of herbicide was too slow to maintain sufficient soil solution concentration. In auloclaved humus soil, breakdown was considerably less pronounced (15% loss in 16 weeks) than in non‐autoclaved samples.Under model conditions (irradiation with ultra‐violet source of 300 W) photo‐destruction of C‐1983 was found to be rapid (90% loss within 13 hours).From roots and leaves of Zea mays, Vicia faba and Phaseolus vulgaris, the same metabolites as given above (compounds [II] and [III]) were recovered in significant amounts. Furthermore, some minor, unidentified labelled compounds and varying amounts of residual radioactivity (not extracted by acetone) were observed. Evolution of 14CO2 was slow. Upon following the breakdown of C‐1983 as a function of time in two weed species, Polygonum convolvulus was demonstrated to metabolize C‐1983 more rapidly than Galinsoga parviflora.The implications of the present results are discussed in terms of the biological breakdown of C‐1983 in soils under field conditions, the susceptibility of different plant species towards C‐1983, and the determination of residue values in plant tissues and soils.Le comportement de la N'‐(4‐chlorophénoxy)‐phényl‐NN‐diméthylurée (C‐1983) dans les sols et dans tes plantesIII. Dégradation dans tes sais et dans les plantes
A RAPID BIOASSAY FOR PEBC AND ITS APPLICATION IN VOLATILIZATION AND ADSORPTION STUDIES
Authors: HOROWITZ M. 
Published: July 2006

Summary. A rapid bioassay for PEBC (S‐propyl‐N‐butyl‐N‐ethylthiolcarbamate) has been developed, based on the measurement of shoot elongation of oat seedlings in Petri dishes in a nearly vertical position. Results are obtained after 48 hr.The bioassay was used to study the relationship between soil moisture and volatilization and adsorption of PEBC. When PEBC was applied to air‐dry soil, no appreciable loss of activity occurred even after 36 days of exposure to a continuous air‐flow. The residual activity of PEBC applied to soils of various moisture contents appears to be related to the initial moisture level. A substantial amount of the compound was adsorbed by air‐dry soil after an exposure of 24 hr to vapours of PEBC. The amount of PEBC adsorbed from the vapour phase after 24 or 72 hr appears also to be related to the moisture content of the soil.Un essai biologique rapide pour U PEBC et son utilisation dans l'étude dt la volatilisation et de l'adiorption du produit
ABSORPTION AND TRANSLOCATION OF HERBICIDES BY THOMPSON SEEDLESS (SULTANINA) CRAPE, VITIS VINIFERA L.
Authors: LEONARD O. A. , LIDER L. A. , GLENN R. K. 
Published: July 2006

Summary. Absorption and translocation of 14C‐labelled herbicides applied in culture solutions lo the roots and in concentrated drops to mature leaves of ‘Thompson Seedless’ (Sultanina) cuttings were studied. Neither 2,4‐D nor paraquat, and only traces of 2,4,5‐T translocated from the roots to the shoot. Dicamba, amitrole, diuron, monuron, simazine and atrazine readily moved from the roots to the shoots. The substituted ureas and s‐triazines were mobile only in the xylem or cell walls (apoplast), while dicamba and amitrole were mobile in the apoplast and symplast (living protoplasm). Both 2,4‐D and 2,4,5‐T moved almost entirely in the symplast. Paraquat moved only slightly in either apoplast or symplast. Stability of the herbicides in the plants varied, as judged by the detection of label in ethanol‐insoluble products. Dicamba was considerably more stable than 2,4,5‐T which, in turn, was more stable than 2,4‐D. Diuron was more stable than either atrazine or simazine. Amitrole largely was converted into ethanol‐insoluble products in 30 days. Paraquat was not extractable with ethanol.Absorption et migration d'herbicides chez une vigne: Thompson Seedless (Sultanina), Vitis vinifera L.
THE EFFECT OF SUPERPHOSPHATE APPLICATION, 2,4‐DB AND GRAZING ON BROOMRAPE (OROBANCHE MINOR SM.) IN A SUBTERRANEAN CLOVER PASTURE
Authors: SOUTHWOOD O. R. 
Published: July 2006

SummaryTwo 5‐year trials were conducted in New South Wales on the control of broomrape (Orobanche minor Sm.), a plant parasite of subterranean clover (Trifolium subterraneum L.) and skeleton weed (Chondrilla juncea L.). Applications of superphosphate to two soils of low phosphorus status stimulated clover growth, which caused a reduction in the number of skeleton weed plants and a decrease in the broomrape population. Similar but less effective control was obtained when subterranean clover pasture was sprayed with 2,4‐DB for skeleton weed control as soon as the clover seedlings had developed trifoliate leaves.In spring, sheep readily grazed the broomrape stems before flowering, causing death of the plants. Autumn application of super phosphate, coupled with grazing of the pasture by sheep, significantly reduced broomrape density.
EFFECTS OF THE HERBICIDES TRIFLURALIN AND CARBETAMIDE ON NODULATION AND GROWTH OF LEGUME SEEDLINGS
Authors: BROCK J. L. 
Published: July 2006

Summary. The effects of pre‐sowing incorporated applications of trifluralin and carbetamide on the growth and nodulation of Trifolium pratense L., T. repens L., T. dubium L. and Lotus pedunculatus Cav. were examined. At rates of 1·0 and 2·0 kg/ha a.i. of trifluralin and carbetamide respectively, nodulation and growth of all legumes was reduced. Root dry weight/plant and nodules/plant were positively correlated, suggesting that the herbicides affected plant growth but not the soil rhizobial population. There were several herbicide rate × legume species interactions.Effets des herbicides trifluraline et carbétamide sur la formation de nodosités et la croissance des plantules de légumineuses
VARIATION IN GROWTH OF SEEDLINGS AND CLONES OF AGROPYRON REPENS (L) BEAUV.
Authors: WILLIAMS E. D. 
Published: July 2006

Summary. The growth of Agropyron repens seedlings, or of clones derived from them, raised from seeds collected from different areas was compared; the growth of seedlings raised from seeds from single spikes and from seeds of a cross of two clones was also compared.The number and length of shoots and the amount of rhizome produced differed between seedlings from different areas. Seedlings with a large weight of rhizomes often had a small weight of shoots. Many of the differences found between seedlings from different areas were confirmed by comparing clones established from some of them. Comparisons of both seedlings and clones showed that the percentage of shoots that developed spikes differed between genotypes; clones with the least weight of rhizome tended to have most weight of spikes. Large variations also occurred between clones established from seedlings from a given area, particularly in the way their dry weight was partitioned between primary and secondary shoots and in the time the spikes emerged.The amount of rhizome per seedling varied greatly between seedlings from seeds from single spikes and from seeds from a cross of two clones. There was some evidence of a negative correlation between per cent shoot and per cent rhizome dry weight with seedlings from single spikes and between number of shoots and number of rhizomes per seedling with seedlings from a cross of two clones. Variation en croissance de plantules issues de semences et de clones d' Agropyron repens (L) Beauv.
HERBICIDAL ACTION OF IODIDE: EFFECT ON CHLOROPHYLL CONTENT AND PHOTOSYNTHESIS IN DWARF BEAN PHASEOLVS VULGARIS
Authors: MYNETT A. , WAIN R. L. 
Published: July 2006

Summary. The toxicity of potassium iodide towards bean plants (Phaseolus vulgaris) is greater in the light than in the dark. Treatment of leaf discs in the dark or the light reduces photosynthetic activity to the same extent, but the loss of chlorophyll is less pronounced in the dark. Iodine behaves similarly but is effective at lower concentrations. Iodide does not inhibit chlorophyll synthesis. Iodine is some 105 times as effective as iodide in inhibition of the Hill reaction in isolated chloroplasts. These results are consistent with the hypothesis that iodine toxicity is a result of intracellular oxidation to iodine. Action herbicide de l'iodure de potassium. Effet sur la teneur en chlorophylle et la photosynthèse sur le haricot nain (Phascolus vulgaris)
LONGEVITY OF CROP AND WEED SEEDS: SURVIVAL AFTER 20 YEARS IN SOIL
Authors: LEWIS J. 
Published: July 2006

Summary. Results are presented of a 20‐year investigation into survival of crop and weed seeds in undisturbed soil. Indications are that seeds reveal their survival potential during the first 4 years; only rarely did species which persisted for this initial period lose all viability in the subsequent 16 years.Deterioration occurred more rapidly in acid peat than in loam soil, and the species which persisted in peat also remained viable in loam soil.The Gramineae were short‐lived in the soil, with the exception of Phleum spp., some seeds of which persisted for 20 years. Most leguminous species persisted for the whole period but not to the same extent as some of the weed species. Of the weeds, the species with the highest percentage seed survival were Ranunculus repens (53%), Chenopodium album (23%) and Rumex crispus (18%).Longévité des semences de plantes cultivées et de mauvaises herbes: survivance après 20 années dans le sol
EFFECT OF MINIMUM SOIL TEMPERATURE ON DIFFERENTIAL DISTRIBUTION OF CYPERUS ROTUNDUS AND C. ESCULENTUS IN THE UNITED STATES*
Authors: STOLLER E. W. 
Published: July 2006

Summary. The response of tubers to low temperatures was investigated to gain insight into a physiological basis for the differential distribution of Cyperus esculentus L. (yellow nutsedge) and C. rotundus L. (purple nutsedge) in the United States. Only C. esculentus tubers survived the winter of 1968–69 in the field at Urbana, Illinois. Less than 10% of C. rotundus tubers survived at 2°C for 12 weeks, whereas more than 95% of C. esculentus tubers survived this treatment. Exposures to ‐2°C for 4 h or longer killed 50% of C. rotundus tubers, whereas ‐ 6·5°C was required to kill 50% of C esculentus tubers. C. rotundus distribution is restricted to regions where the soil seldom freezes, whereas C. esculentus is distributed in regions where the soil temperatures often get below freezing. Survival of C. esculentus tubers in soil which frequently freezes may account for its wide distribution. Death of C. rotundus tubers in soils which freeze apparently is the reason why the species is restricted to the southeastern and southwestern regions of the U.S.A. L'Influence de la température du sol sur la répartition différentielle de Cyperus rotundus et de Cyperus esculentus aux Etats‐Unis