bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors affecting the strength of undisturbed cores from soils with low structural stability
Authors: YOUNG I. M. , MULLINS C. E.
Published: July 2006

Undisturbed core samples of two similar sandy clay loam soils (Big Ground and Plum Orchard) were equilibrated at matric potentials of −0.01, −0.1 and −1 MPa and tested for indirect tensile strength (ITS) and unconfined compressive strength (UCS). Rate of deformation was found to have significant and large effects on the measured ITS and UCS. In general, both ITS and UCS increased with increasing deformation rates although, particularly for UCS tests, the effect was variable. For ITS, the effect of rate of deformation was attributed to water having insufficient time to move towards any incipient failure plane. For UCS, the effect of rate of deformation was partly attributed to loss of moisture during loading, since samples strained at lower deformation rates generally had lower moisture contents; and partly to the different modes of failure seen. ITS and UCS of Big Ground were invariably higher than those of Plum Orchard at all matric potentials. This was attributed to Big Ground having been under an intensive management system for approximately 10 years longer than Plum Orchard.

Simple pretreatment effects are also considered. In a comparison of measured and theoretically predicted ITS and UCS, theory provided good estimates of measured strengths of samples equilibrated at −0.1 MPa, although samples were considerably weaker than theoretically predicted at −1 MPa.
Aluminium contamination of acid soil solution isolated by means of porcelain suction cups: a reply to a paper by Hughes & Reynolds (1990) and an interpretation of aluminium release
Authors: RAULUND‐RASMUSSEN K.
Published: July 2006

Possible aluminium contamination of acid soil solutions isolated by use of porous porcelain suction cups (‘P.80 type’) was reported by Raulund‐Rasmussen (1989). The aluminium release was explained by a proton‐induced dissolution of cup material. Hughes & Reynolds (1990) suggested that the aluminium release and proton consumption could be explained by an ion‐exchange reaction. In an attempt to understand the mechanism and thereby also the usefulness of suction cups, laboratory experiments were carried out to define mineralogical and chemical composition, stability under acid conditions, cation exchange capacity, and reactivity under conditions relevant to the field.

The cups consisted of mullite and corundum (65% Al2O3) as shown by X‐ray diffraction analysis. The cation exchange capacity of the cups was too low (0.65 μmolc per cup) to explain the observed contamination of isolated soil solution. Ground cup material dissolved slowly in acid. Investigations on whole cups showed that aluminium release to acid test solutions depended on the time of exposure. It is concluded that porcelain suction cups may lead to contamination of isolated soil solution depending on: (i) the intake rate, (ii) the rinsing procedure before sampling, and (iii) the composition of the soil solution (pH and aluminium ion activity being important parameters).
Nitrous oxide production and denitrification in Scottish arable soils
Authors: ARAH J. R. M. , SMITH K. A. , CRICHTON I. J. , LI H. S.
Published: July 2006

Nitrous oxide (N2O) emissions and concentrations in the soil atmosphere were measured at a number of sites of differing soil type in south‐east Scotland between 1985 and 1988. Concentrations followed log‐normal distributions and were significantly affected by soil type, tillage treatment, and nitrate application rate. The shape of the profiles suggested significant consumption in the upper 5 cm, making calculations of emission rates using Fick's Law unsatisfactory. Emission rates measured using closed flux chambers were at least one order of magnitude smaller from heavier‐textured arable soils than from lighter ones.

Denitrification fluxes measured by field application of the acetylene inhibition technique were lowest in a clay loam, and highest in an alluvial sandy loam; this was attributed to a failure to achieve a satisfactory distribution of acetylene in the heavier soil. Denitrification rates in soil cores generally exceeded measured surface fluxes; incubation at decreased oxygen concentrations typical of those measured in the field produced a further significant increase. Core incubation should be used as an alternative to in situ field measurement only if the oxygen concentration in the incubation vessels is adjusted to mimic that in the field; otherwise denitrification rates may be significantly underestimated.
Poorly ordered hydrous Fe oxides, colloidal dispersion and soil aggregation. II. Modification of silty soil aggregation with Fe(III) polycations and model humic macromolecules
Authors: BARTOLI F. , PHILIPPY R. , BURTIN G.
Published: July 2006

Poorly ordered ferrihydrites, more or less associated with synthetic humic macro‐molecules, were added to a poorly structured temperate silty soil. Manipulation of the net soil charge through these additions was measured by potentiometric titration and cation exchange capacity. The consequences of anchoring positively charged Fe hydrous oxides on negative permanent clay surface charges were studied. Both cementation and aggregate water‐stability increased with increase in adsorbed iron. The aggregation process was studied by using micromorphology and ultramicromorphology, water retention curves, mercury porosimetry and a fractal approach. Aggregate water‐stability was studied when the soils were air‐dried, with some irreversible aggregation, and oven‐dried or wetted from – 1.5 MPa to – 1 kPa thereafter. Soils with added Fe(III) polycation–humic macro‐molecule associations were less positively charged, less cemented and less stable than soils amended with Fe(III) polycations alone. The effect of these treatments on slaking is discussed.
The effect of time on the competition between anions for sorption
Authors: BARROW N. J.
Published: July 2006

Solutions of phosphate and of selenite were gently mixed with a soil, both separately and in combination, for periods ranging from 15 min to 30 days. For both anions, the solution concentration continued to decrease throughout the period, but the decrease was more marked for phosphate. Competitive effects were smallest after brief periods of mixing, and increased with time. Phosphate was a more effective competitor for sorption than selenite, and its competitive advantage increased with time.

The observed effects were closely described by a mechanistic model. According to the model, competition was largely through changes in the electric potential of the surface rather than through decreases in the number of vacant adsorption sites. This explained why competition effects were initially small. This was especially so for phosphate, which was modelled as having a marked continuing diffusive penetration of the surface. The decrease in electric potential associated with that penetration decreased the surface concentration of selenite and so decreased the rate of penetration of selenite. By the end of the experiment this was the most important aspect of the competitive effect of phosphate on selenite.
Comparison of different models for phosphate sorption as a function of the iron and aluminium oxides of soils
Authors: FREESE D. , van der ZEE S. E. A. T. M. , van RIEMSDIJK W. H.
Published: July 2006

Phosphate sorption on topsoil and subsoil samples from different soils located in the eastern part of Germany was studied. Two models were fitted to sorption data obtained after 4 and 40 d of gentle shaking. The models differ with respect to the fractions of iron and aluminium (hydr)oxides that are considered and whether the phosphate initially sorbed in the soil is taken into zccount. Oxalate‐extractable P, (Pox), appears to be a major part of the total soil P. The total P sorption measured, F, was predominantly related to the amounts of amorphous iron (Feox) and aluminium (Alox). A significant relation between crystalline iron (Fed– Feox) and total P sorption was not found. Reversibly adsorbed phosphate (Pi), measured after 40 d reaction time, was a function of clay content and content of amorphous iron and aluminium (hydr)oxides.
Microbial contribution to sulphate mobilization after liming an acid forest soil
Authors: MARSCHNER B.
Published: July 2006

Sulphate release from unsterilized and γ‐irradiation sterilized soil samples was studied in leaching funnels over a 22‐week incubation period. In unsterilized soil samples, lime addition to the acid forest topsoil caused an immediate increase in extractable sulphate, but enhanced sulphate release rates were detectable only during the first 4 weeks of incubation. Soil samples from an adjacent five‐year‐old limed plot displayed significantly higher sulphate release rates than the control throughout the experiment. The cumulative amount of sulphate extracted from the unsterilized treatments was modelled with parabolic functions and reached 4.6%, 6.8% and 8.2% of the initial total S‐contents of the control, the lime treatment and limed plot respectively. Mineral‐N release was also greatest in the samples from the old limed plot while fresh lime additions reduced net N‐mineralization due to microbial immobilization. In the sterilized samples, γ‐irradiation initially caused an increase in extractable sulphate and ammonium which is mainly attributed to the destruction of microbial biomass. After the second week, no further differences in extractable sulphate were detectable between the treatments. After 22 weeks, between 7 and 9 mg SO42− ‐S kg−1 soil was released from the sterilized samples which was 25–50% of the respective amounts in the unsterilized samples. A similar relationship was found for N. The data indicate that even 5 years after lime addition the observed increased sulphate concentrations in the soil solution can be attributed to enhanced microbial activity.
A modified biometer flask for the measurement of mineralization of 14C‐labelled compounds in soil
Authors: HAIGH S. D.
Published: July 2006

The Organisation for Economic Cooperation and Development (OECD)‐recommended biometer flask (OECD Guideline 304A) was modified to allow rapid and accurate sampling of large numbers of flasks during long‐term soil biodegradation experiments. Use of the OECD flask involves tedious manipulation each time the flasks are sampled. The transfer of alkali to and from the side‐arm reservoir, followed by dilution, is open to operator error and is time consuming. The new flask was found to give comparable or higher recoveries of CO2 compared to the OECD‐recommended apparatus whilst minimizing the manipulation of 14C‐loaded alkali. By avoiding dilution of the alkali trap, the sensitivity of the test is increased by an order of magnitude and the sampling time is reduced by two‐thirds.
Estimation of the diffusion coefficients of adsorbed and non‐adsorbed solutes in soil
Authors: COLLIS‐GEORGE N. , GEERING H. R.
Published: July 2006

A method is proposed which follows Darrah's experimental procedure and takes advantage of a mathematical solution provided by Carslaw & Jaeger to estimate the diffusion coefficients of adsorbed and non‐adsorbed solutes in soil.

The method requires only the values of the concentration of the solute at the input face of a uniform column of soil, Cs, and of the total amount, Qt, that has entered the soil after a specified time during which the surface of the block is in contact with a thin porous pad containing a known initial amount of solute, Q0, at concentration C0, expressed in the same units as Cs. In the Cs/C0 vs. Qt/Q0 space there is a unique relationship between the effective diffusion coefficient, De, of the solute in the soil and the contact conductance for this solute, h, between the pad and the soil surface.

The proposed procedure is firstly to determine De, and h for a non‐adsorbed solute in the experimental soil using the experimental values of Cs/C0 and Q/Q for that solute. This value of De, gives the diffusion impedance factor for the solute in the soil, f, which is assumed also to apply to adsorbed solutes. A first estimate of the effective diffusion coefficient of an adsorbed solute, 1Dea, is then made using f and the diffusion coefficient of the free solute in water, DL, obtained from the literature (i.e. 1Dea= DLf). Only if the solute is weakly adsorbed will the values of Cs/C0, and Qt/Q0 lie in Cs/C0, vs. Qt/Q0, space as defined by 1Dea and the contact conductance, h. Instead a second space relating Cs/C0 and Qt/Q0, is now constructed from nominated values of h and De, where De, is defined in terms of 1Dea, the adsorption coefficient, F, and the volumetric moisture content of the soil, θ. The position of the experimental values of Cs/C0, and Qt/Q0 within this new space defines h and the actual De, and F of the solute as it diffuses and is adsorbed in the soil.

The advantages and limitations of the method are discussed. In particular, the method assumes that the adsorption process is linear and reversible.
The solidsolution equilibria of lead and cadmium in polluted soils
Authors: JOPONY M. , YOUNG S.D.
Published: July 2006

A 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

The 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

A 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

A 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

The 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

Water‐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 plantes

III. 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

Two 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
The response of hill bracken and the associated pasture to applications of picloram and dicambra
Authors: FARNWORTH J. , DAVIES G. M.
Published: July 2006

Summary: Résumé: Zusammenfassung

Picloram and dicamba applied as sprays or granules at equal doses reduced the vigour of bracken, and there was a corresponding increase in pasture yield. Yield of pasture dry matter and digestible organic matter was increased by over 400% on picloram plots compared with untreated plots and Agrostis spp. became dominant in the sward. Picloram produced the greatest reduction in bracken vigour. Vigour was assessed in terms of dry weight of frond laminae per unit area and total available rhizome carbohydrate per unit area. Higher doses, and granular rather than spray applications of both herbicides were most effective in reducing bracken vigour. Out of twenty‐one correlations tested over a 3‐year period, bracken frond lamina dry weight yield showed the best relationship with pasture dry matter yield.

Réponse de la fougére et de la pâture associée à des applications de piclorame et de dicamba

Le piclorame et le dicamba appliqués sous forme liquide ou sous forme de granulés, à des doses égales, ont réduit la vigueur de la fougàre et il s'est manifesté un accroissement correspondant du rendement de la pâture. Le rendement de la pâture en matiàre sàche et en matiàre organique digestible a été augmenté de plus de 400 % dans les parcelles traitées au piclorame, par rapport aux parcelles non traitées et l'Agrostis spp est devenu dominant dans la prairie. Le picloramé a provoqué la plus forte réduction de la vigueur de la fougàre. La vigueur a été exprimée en termes de poids sec de feuilles de frondes et en carbohydrates totaux disponibles dans les rhizomes, par unité de surface. Les doses les plus fortes et les granulés, plus que les pulvérisations, furent les plus efficaces quant à la réduction de la vigueur de la fougàre. Des 21 corrélations examinées durant une période de trois ans, il ressort que le rendement, en poids sec, des feuilles de frondes de fougàres a montré la meilleure relation avec le rendement en matiàre sàche de la pâture.

Die Reaktion von Adlerfarn und der von ihm besiedelten Weide auf Behandlungen mit Picloram und Dicamba

Sprintzungen und entsprechende Aufwandmengen als Granulate von Picloram und Dicamba verminderten die Wuchsigkeit des Adierfarns und bewirkten einen Ertrags‐zuwachs der Weide. Der Ertrag an Trockensubstanz der Weide und die verdauliche organische Substanz, nahmen in den Picloramparzellen, verglichen mit Unbehandelt, um über 400 % zu und Agrostis spp. wurden vorherrschend. Picloram drängte den Adlerfarn am stärksten zurück. Die Wüchsigkeit wurde an Hand des Wedeltrockengewichts je Flächeneinheit und verfägbarer Rhizomkohlenhydrate je Flächeneinheit gemessen. Bei beiden Herbiziden wurde der Adlerfarnwuchs durch höhere Aufwandmengen und Anwendung in Granulat‐form stärker vermindert als durch Spritzungen. Von den Versuchsergebnissen aus drei Jahren, zeigten von 21 geprüften Korrelationen das Wedeltrockengewicht des Adierfarns mit dem Trockensubstanzertrag der Weide, die beste Beziehung.
Activated‐carbon and ash‐carbon effects on the adsorption and phytotoxicity of diuron
Authors: TOTH J. , MILHAM P. J.
Published: July 2006

Résumé: Zusammenfassung: Summary

Carbon produced by burning paspalum (Paspalum dilatatum L.) under a wide range of conditions (ash‐C) adsorbed appreciable quantities of diuron from aqueous solution. However, commercially activated‐C was a more efficient adsorbent than any of the ash‐C products whose activity was related to their conditions of formation. Broadcast activated‐C at a C/diuron ratio ≤5/1 (w/w) prevented death of barley (Hordeum vulgare L.) seedlings receiving the highest diuron treatment (32 kg ha−1); although 0–8 kg ha−1 killed the plants in its absence. Only one of the two ash‐C products tested caused a significant reduction in the phytotoxicity of ≥16 kg diuron ha−1. Death of plants was delayed. However, the bioassay was not sufficiently sensitive to measure the smaller reduction in phytotoxicity caused by the other ash‐C treatment.

Effets d'un charbon actif et de charbons de cendres sur l'adsorption et la phytotoxicité du diuron

Les charbons des cendres obtenues en faisant brüler du paspalum (Paspalum dilatatum L.) dans une série étendue de conditions ont adsorbé des quantités appreciates de diuron a partir d'une solution aqueuse. Toutefois, un charbon actif du commerce se révéla comme un adsorbant plus efficace qu'aucun des charbons obtenus dont l'activité fut en rapport avec les conditions de leur obtention. Un poudrage avec du charbon actif dans une proportion pondérale de 5 parties au minimum de carbon pour une partie de diuron a prévenu la destruction de plantules d'orge (Hordeum vutgare L.) ayant reçu le traitement á la dose la plus élevée de diuron (32 kg/ha) alors qu'en l'absence de charbon actif, les plantules furent tuées á la dose de 0.8 kg/ha. Un seul des deux charbons de cendres essayés provoqua une reduction significative de la phytotoxicité du diuron á la dose de 16 kg/ha. La mort des plantes fut retardée. Toutefois l'essai biologique ne fut pas suffisamment précis pour mesurer la réduction plus faible de phyiotoxicité résultant du traitement avec l'autre charbon de cend res.

Die Wirkung ton Aktivkohle und Aschekohlenstoff auf die Adsorption und Phytotoxizität von Diuron

Aschekohlenstoff, der auf versehiedene Weise durch Verbrennen von Paspalum ditatatum L. gewonnen wurde, adsorbierte aus wässerigen Lösungen beträchtliche Mengen an Diuron. Die vom Handel bezogene Aktivkohle wiir uber ein starkeres Adsorbens als jedes der Aschekohlenstolf‐Produkte. Ihre Wirksamkeit hing von der Art der Herstellung ab. Wenn Aktivkohle in einem Verhältnis zu Diuron von ≥5/1 (Gew./Gew.) breitwörfig ausgebracht wurde, konnte bei der höchsten Diuronbchandlung (32 kg ha−1) das Absterben von Gerstesämlingen (Hordeum vutgare L.) verhindert werden, während hereits 0.8 kg ha−1 Diuron alieine die Pflanzen abtöteten. Nur eines der beiden geprüften Aschekohlenstoff‐Produkte bewirkte bei ≤16 kg ha−1 Diuron eine gesicherte Reduktion der phytotoxischen Wirkung indem das Absterben der Pflanzen verzögert wurde. Um die geringere Wirkung des anderen Produkls zu erfasscn. war der Biotest zu unempfindlich.
The in vitro sensitivity of some species of Chlorophyceae to a selected range of herbicides
Authors: CULLIMOKE D. ROY
Published: July 2006

A survey was undertaken to establish the sensitivity of seventeen algal strains belonging to the Chlorophyceae to a selected range of herbicides up to a concentration maximum of 10 ppm under in vitro conditions. The herbicides were found to vary considerably in their toxicity to algae and a sequence was established based upon the magnitude of this toxicity: diuron > bromacil > paraquat> monuron> diquat> linuron> 2, 4‐DB >barban> dicamba, dichlobenil, dalapon, picloram> bromoxynil, 2,3,6‐TBA > 2.4‐DP. 2,4,5‐T and EPTAM. Of the algae, the most sensitive genera were Hormidium and Haematococcus, and the strain most sensitive to a wide range of herbicides was Hormidium barlowi (strain 335/la).
Absorption and efflux of chloro‐s‐triazines by Setaria roots*
Authors: ORWICK P. L. , SCHREIBER M. M. , HODGES T. K.
Published: July 2006

The absorption and loss of four chloro‐s‐triazines was investigated in excised roots of four Setaria taxa. Different taxa absorbed the various triazines at different rates. In general, triazine absorption was greater at 2°C than at 22.5°C, and absorption rates were linear functions of external concentrations.

Efflux studies showed marked differences in the rate of loss of 14C‐atrazine, 14C‐simazine, and 14C‐propazine from root sections of robust white foxtail (Setaria viridis var. robustaalba Schreiber). The roots lost 14C‐atrazine very quickly, and the loss was similar in either water or 12C‐atrazine. Atrazine appears to be restricted to the apoplast of the root. 14C‐atrazine was lost more rapidly than either 14C‐simazine or 14C‐propazine to water or to solutions containing the unlabelled herbicide. Efflux of 14C‐simazine was greater than that of 14C‐propazine to solutions of CaCl2. From the pattern of efflux, it was concluded that 14C‐simazine and 14C‐propazine accumulated in the root symplast. Furthermore, the decreases in chloro‐s‐triazine absorption in the presence of metabolic inhibitors (dinitrophenol, sodium arsenite) may suggest that 14C‐simazine and 14C‐propazine entered the symplast by an energy‐dependent process.
Studies on the mode of action of asulam in bracken (Pteridium aquilinum L. Kuhn) I. Absorption and translocation of [14C]asulam
Authors: VEERASEKARAN P. , KIRKWOOD R. C. , FLETCHER W. W.
Published: July 2006

Studies of the absorption and translocation of foliage‐applied ring‐labelled [14C]asulam [methyl (4‐aminobenzenesulphonyl) carbamate] were carried out using glasshouse and field‐grown bracken plants. Translocation of 14C from the treated frond was primarily according to a 'source to sink’pattern with intense accumulation of radioactivity in the metabolically active sinks viz. rhizome apices, frond buds, root tips and young frond tissue. In the case of field bracken, translocation and distribution of 14C was extensive in the rhizome system, accumulation occurring in the active as well as dormant buds situated on the non‐frond‐bearing and storage rhizome branches. Treatment of fully expanded fronds with 100μl of [14C]asulam (1 mg, 1.0–1.5 μCi) as 2 μl droplets resulted in a rapid initial uptake during the first week, followed by progressive entry and distribution with time. Basipetal translocation to the rhizome system was positively correlated with total uptake. High humidity (95%) and high temperature (30°C) stimulated uptake and subsequent basipetal translocation to a considerable degree. Uptake was greater through the stomatal‐bearing abaxial than through the adaxial cuticle. Incorporation of a surfactant (Tergitol‐7, 0.1%) increased penetration by up to 30%. Uptake declined markedly as the frond aged, while translocation was predominantly acropetal in young treated fronds, becoming exclusively basipetal when the fronds matured. Optimum uptake and maximum distribution of [14C]asulam in the rhizome and its associated buds was achieved when treatments were applied to almost fully expanded fronds. The translocated 14C (asulam and possibly some of its metabolites) showed a considerable degree of persistence in the rhizome system, 8% of the applied activity still remaining in the rhizome 40 weeks after treatment.
Laboratory trials of a new triazine herbicide (DPX 3674) on various aquatic species of macrophytes and algae
Authors: FOWLER M. C.
Published: July 2006

The new herbicide 3‐cyclohexyl‐6‐(diméthylamino)‐1‐methyl‐1,3,5‐triazine‐2,4 (1H,3H)‐dione (DPX 3674), effective in controlling various terrestrial plants, was found in glasshouse trials to control Myriophyllum verticillatum, Potamogeton pectinatus and Vaucheria dichotoma at 1.0 ppm and Rhizoclonium hieroglyphicum and Cladophora glomerata at 0.5 ppm. A rapid reduction of the dissolved oxygen content of the water occurred during the first few days of treatment.
Detoxification of glyphosate in soil
Authors: TORSTENSSON N. T. L. , AAMISEPP A.
Published: July 2006

Detoxification of glyphosate in not‐autoclaved and autoclaved soils was followed by bioassay with wheat. Comparisons are made with detoxification of MCPA under similar conditions followed by bioassay with spring rape. The well known pattern for microbial metabolism of MCPA with a ‘lag’‐phase preceding the rapid degradation was shown. The initial rapid inactivation of glyphosate is by adsorption, but the results also clearly indicate that the further disappearance of activity mainly depends on microbial degradation. Glyphosate does not seem to sustain microbial growth, which indicates that it is degraded by co‐metabolism. In autoclaved soil the possibility of a slight chemical degradation or an adsorption that becomes stronger with time could not be excluded.
The fate of the herbicide chlortoluron and its possible degradation products in soils
Authors: SMITH A. E. , BRIGGS G. G.
Published: July 2006

Chlortoluron hadàhalf‐tire in soil of 4–6 weeks. The only metabolite identified was monomethyl chlortoluron, half‐life 8 weeks. 3‐Chloro‐4‐methylphenylurea hadàsimilar half‐life but was not detected in soils treated with chlortoluron or monomethyl chlortoluron suggesting that 3‐chloro‐4‐methylaniline was formed directly from monomethyl chlortoluron. This aniline hadàhalf‐life of 1–2 days in soil, initial concentrations above 5 ppm yielding dimers and trimers predominantly C — N linked. Neither the aniline nor polymeric products were detected in chlortoluron treated soils, presumably because slow formation of the aniline was followed by rapid degradation which kept concentration low.