bluuebunny/crossref_metadata_2025 huggingface dataset:
Fragipan formation in argillic brown earths (Fragiudalfs) of the Milfield Plain, north‐east England. II. Post Devensian developmental processes and the origin of fragipan consistence
Authors: PAYTON R. W.
Published: July 2006

Pedogenetic processes following a permafrost stage of development in four argillic brown earths with fragipans (Glossic and Ochreptic Fragiudalfs) are investigated by soil microscopy, including SEM observations of unimpregnated soil material, and by determination of clay mineralogy. Micromorphology of the apparently massive fragipan confirms both the presence of subhorizontal fissures infilled with illuvial deposits separating dense lenticular structures formed by ice‐lens growth, and former vertical fissures formed by dessication on freezing with subsequent widening by ice‐vein development. The firmness and brittle failure of the fragipans are attributed to a closely‐packed, well‐graded matrix of skeleton grains bonded by clay bridges consisting of non‐swelling illite and chlorite and to weak interconnection of macrovoids. Weak cementation is rejected as an explanation of fragipan consistence. Sequential stages of particle translocation have been critical to fragipan formation. High bulk density is attributed not only to irregular compression and contraction of the soil matrix under permafrost conditions but also to the infilling of voids by illuvial silt and clay. The full development of the fragipans has depended on Flandrian clay migration which has contributed to clay‐bridge formation, void infilling and localized seasonal impedance of drainage resulting in eluviation of iron oxides, the development of grey polygonal patterning, and processes of degradation at the pan surface leading to glossic features.
Structural collapse and strength of some Australian soils in relation to hard setting: II. Tensile strength of collapsed aggregates
Authors: GUSLI S. , CASS A. , MACLEOD D.A. , BLACKWELL P.S.
Published: July 2006

The strength of soils is related to structural stability. Aggregate structure which collapses on wetting may set to a hard, consolidated layer on drying (hard setting). This process may be moderated by suction wetting and possibly by application of calcium, but the mechanism of moderation is not clear. We investigated the collapse‐strength relationship and the mechanism by which wetting method and calcium act to reduce strength in hard setting and non‐hard setting soils. Indirect tensile strength of aggregate beds that had been wetted with water or 10mM CaCI2 by rapid flooding or at a suction of 200 mm, was measured after draining to various suctions and drying at 40°C.

The greater the volume strain during wetting and draining, the greater the tensile strength. Beds that were suction wetted, either with water or calcium solution, showed minimal collapse and did not develop high strength on drying. Water‐flooded beds had the greatest dry strength while beds flooded with calcium solution developed significantly lower strength. The critical factor determining tensile strength of the beds appeared to be the presence of large (>75 μm diameter) pores. The greater the volume strain on wetting, the smaller the proportion of larger pores and the greater the tensile strength on drying. Flood wetting caused more loss of large pores and closer packing of particles. Wetting with calcium solution did not affect the degree of collapse compared with that of water alone but did produce beds with larger pores than when wetted with water. Consequently the strength of the calcium‐wetted beds was lower.
Changes in the chemistry of soil solution and acetic‐acid extractable P following different types of freeze/thaw episodes
Authors: VAZ M.D. RON , EDWARDS A.C. , SHAND C.A. , CRESSER M.S.
Published: July 2006

Freezing significantly influences the amount and chemical form of extractable soil phosphorus and, therefore, has important consequences regarding plant nutrient availability. Much of the current evidence relies on field‐based observations and tends to be rather contradictory. The present work reports the specific effects various freezing episodes have on phosphorus availability. Experimental treatments included the freezing rate and the time soil remained frozen together with the number of freeze/thaw cycles. These laboratory incubations used two soils, an iron humus podzol and a peaty podzol, sub‐samples of which were equilibrated at three different soil‐moisture contents. Concentrations of phosphorus in soil solutions and acetic acid extracts (Ac‐P) were measured. Freezing had the greatest effect on the organic (Op) horizon of the peaty podzol, where the amounts of total dissolved phosphorus (TDP) and Ac‐P increased from 0.58 to 3.21 and from 11.8 to 19.3 mg P kg−1, respectively. TDP in soil solution was subdivided into three broad categories, dissolved (molybdate) reactive (MRP), organic (DOP) and condensed (DCP). The rather variable effect that freeze/thaw episodes had on these fractions highlighted the problems associated with attributing the ‘freezing effect’ to any single process.
The relationship between structure and the hydraulic conductivity of soil
Authors: CRAWFORD J.W.
Published: July 2006

A random fractal matrix comprising a hierarchical aggregation of primary structural elements is used to capture the characteristics of a heterogeneous soil structure with a tortuous pore space. The influence of heterogeneity of both the solid matrix and the pore space, as well as the shape of the pore boundary, on the saturated and unsaturated hydraulic conductivity is studied. For such random structures, the fractal (Hausdorff) dimension alone is not enough to characterize the structure from the point of view of fluid flow and additional characterizations are introduced. The porosity, ρp, of the primary elements has a critical value, ρc. With probability 1, both the saturated and unsaturated conductivities are found to be dependent as a power law on the length scale, L, at which the measurement is made when ρp>ρc. When ρp<ρc, only the unsaturated conductivity is scaling in length scale, while the saturated conductivity becomes dominated, with probability close to 1, by the conductivity of the largest connecting pores in the structure, i.e. preferential pathways. The relationships between the parameters of the power laws and structure are derived and are found to depend on the fractal (Hausdorff) and spectral dimensions of the solid matrix, denoted dm and respectively. A discussion of the importance of these results for the interpretation and extrapolation of measurements is presented, and the implications for variability and predictability of the hydraulic properties of soil is discussed.
Seasonal variation in habitat use by salmon, Salmo salar, trout, Salmo trutta and grayling, Thymallus thymallus, in a chalk stream
Authors: RILEY W. D. , IVES M. J. , PAWSON M. G. , MAXWELL D. L.
Published: July 2006

Abstract  A portable multi‐point decoder system deployed in a tributary of the River Itchen, a southern English chalk stream, recorded the habitats used by PIT‐tagged juvenile salmon, Salmo salar L., trout, Salmo trutta L. and grayling, Thymallus thymallus L., with a high degree of spatial and temporal resolution. The fishes’ use of habitat was monitored at 350 locations throughout the stream during September/October 2001 (feeding period) and January/February 2002 (over‐wintering period). Salmon parr tended to occupy water 25–55 cm deep with a velocity between 0.4 and 1.0 m s−1. During both autumn and winter, first year salmon (0+ group) were associated with gravel substrate during the daytime and aquatic weed at night. In autumn, 1+ salmon were strongly associated with hard mud substrates during the day and with marginal tree roots at night. In winter, they were located on gravel substrate by day and gravel and mud at night. Trout were associated with a greater range of habitats than salmon, generally occupying deeper and faster water with increasing age. During the autumn, 0+ trout were located along shallow (5–10 cm) and slow (−0.1–0.4 m s−1) margins of the stream, amongst tree roots by day and on silty substrates at night. During winter the 0+ trout occupied silty substrates at all times. As age increased, trout increasingly used coarse substrates; hard mud, gravel and chalk, and weed at night. All age groups of grayling (0+, 1+ and 2+) tended to occupy hard gravel substrate at all times and used deeper and faster water with increasing age. The 1+ and 2+ groups were generally found in water 40–70 cm deep with a velocity between 0.3 and 0.5 ms−1, whilst the 0+ groups showed a preference for shallower water with reduced velocity at night, particularly in the winter. There were greater differences in the habitats used between species and age groups than between the autumn and winter periods, and the distribution of fish was more strongly influenced by substrate type than water depth or velocity. The results are discussed in relation to the habitat requirements of mixed salmonid populations and habitat management.
The oral health and treatment needs of schoolchildren in Trinidad and Tobago: findings of a national survey
Authors: NAIDU R. , PREVATT I. , SIMEON D.
Published: July 2006

Summary.  Objective.  To describe the oral health and treatment need of schoolchildren in Trinidad and Tobago.

Design and method.  Cross‐sectional survey using stratified cluster sampling. Participants were children in primary (aged 6–8 years) and secondary school (aged 12 and 15 years). Main outcome measures were DMFT/dmft, treatment need, and fluorosis.

Results.  Examinations were completed on 1064 children. The dmft of the 6–8‐year‐olds was 2·54 (95% CI = 2·32, 2·76). For 12‐year‐olds, the DMFT was 0·61 (95% CI = 0·51, 0·71), whereas for 15‐year‐olds, the DMFT was 1·06 (95% CI = 0·87, 1·25). Most of the caries experience in 6–8‐year‐olds was from decayed teeth. Sixty‐seven per cent of the sample (95% CI = 64%, 69%) had some type of treatment need. Most frequently occurring need was for fillings at 42% (95% CI = 40%, 44%) with 28% (95% CI = 26%, 31%) of the total sample needing two or more surface fillings, followed by fissure sealants at 33% (95% CI = 30%, 36%) and caries‐arresting care at 12% (95% CI = 10%, 14%). Extraction of one or more teeth was needed in 13% (95% CI = 11%, 15%) of children. Rates of fluorosis were negligible.

Conclusion.  The caries experience of 12‐ and 15‐year‐old children were low but was high for schoolchildren aged 6–8 years, in terms of prevalence and severity. Effective oral health promotion strategies need to be implemented to improve the oral health of primary schoolchildren in Trinidad and Tobago.
A model‐independent test for the presence of regulatory equilibrium and non‐random structure in island species trajectories
Authors: Golinski Michael , Boecklen William J.
Published: July 2006

Aims  To test a key prevision of the dynamic equilibrium theory of island biogeography, namely that changes in species numbers on islands over time (hereafter, species trajectories) are equilibrial, and to characterize aspects of the dynamical properties of species change over time using a model‐independent test.

Methods  We tested for regulatory equilibrium and non‐random structure in species numbers through time by comparing observed correlation coefficients at lag‐k for species trajectories from four true islands and two habitat islands. First, we estimated the shape of the autocorrelation function for each observed species trajectory by calculating correlation coefficients of the observed data between pairs of values Nt−k and Nt separated by lag‐k (k = 1, 2, …, N − 1). Second, we tested the observed correlation coefficients at each lag against a distribution of correlation coefficients generated by randomly ordering observed numbers in the species trajectories.

Results  The patterns of autocorrelation functions for all but one of the observed species trajectories did not exhibit evidence of regulatory equilibrium, and, in fact, closely matched what would be expected from a non‐stationary or ‘random walk’ process. The majority of the correlation coefficients generated from the observed species trajectories did not deviate significantly from correlation coefficients produced by the randomized trajectories. However, there was strong evidence of unusual positive autocorrelation at small time lags for birds on islands measured annually (2‐ to 4‐year lags) and for arthropods on islands measured weekly (7‐ to 8‐week lags), suggesting some degree of structure in change in species richness over time.

Main conclusions  The autocorrelation function patterns for all but one of the observed species trajectories showed various forms of non‐stationarity. These types of patterns suggest that the numbers of species through time gradually wandered away from their initial sizes. Our model‐independent test of individual correlation coefficients revealed significant structure in the observed species trajectories. These trajectories appear to be non‐random at relatively short lag intervals, indicating a process with short memory.
Transcriptome profiling uncovers metabolic and regulatory processes occurring during the transition from desiccation‐sensitive to desiccation‐tolerant stages in Medicago truncatula seeds
Authors: Buitink Julia , Leger Jean J. , Guisle Isabelle , Vu Benoit Ly , Wuillème Sylvie , Lamirault Guillaume , Bars Alice Le , Meur Nolwenn Le , Becker Anke , Küster Helge , Leprince Olivier
Published: July 2006

To investigate regulatory processes and protective mechanisms leading to desiccation tolerance (DT) in seeds, 16086‐element microarrays were used to monitor changes in the transcriptome of desiccation‐sensitive 3‐mm‐long radicles of Medicago truncatula seeds at different time points during incubation in a polyethylene glycol (PEG) solution at −1.7 MPa, resulting in a gradual re‐establishment of DT. Gene profiling was also performed on embryos before and after the acquisition of DT during maturation. More than 1300 genes were differentially expressed during the PEG incubation. A large number of genes involved in C metabolism are expressed during the re‐establishment of DT. Quantification of C reserves confirms that lipids, starch and oligosaccharides were mobilised, coinciding with the production of sucrose during the early osmotic adjustment. Several clusters of gene profiles were identified with different time‐scales. Genes expressed early during the PEG incubation belonged to classes involved in early stress and adaptation responses. Interestingly, several regulatory genes typically expressed during abiotic/drought stresses were also upregulated during maturation, arguing for the partial overlap of ABA‐dependent and ‐independent regulatory pathways involved in both drought and DT. At later time points, in parallel to the re‐establishment of DT, upregulated genes are comparable with those involved in late seed maturation. Concomitantly, a massive repression of genes belonging to numerous classes occurred, including cell cycle, biogenesis, primary and energy metabolism. The re‐establishment of DT in the germinated radicles appears to concur with a partial return to the quiescent state prior to germination.
DAS VERHALTEN VON RHIZOMEN DER QUECKE (AGROPYRON REPENS) GEGEN TROCKENE LUFT
Authors: GRÜMMER GERHARD
Published: July 2006

Zusammenfassung. 1. Herausgeschnittene Stücke von Rhizomen der Quecke sind nur dann zur Entwicklung einer neuen Pflanze befähigt, wenn sie eine unbeschädigte und voll ausgebildete Knospe tragen.

2. Rhizomteile von 1 cm Länge mit normal ausgebildeter Knospe konnten zu einem hohen Prozentsatz neue Pflanzen bilden. Wurden die Stücke in Längsrichtung halbiert, so kamen nur noch etwa die Hälfte der mit Knospen versehenen Teile zur Entwicklung. Selbst Stücke von nur 3 mm Länge mit intakter Knospe konnten noch zu 30% normale Pflanzen bilden.

3. Mit zunehmender Verfärbung der Rhizome nach Braun und Schwarz nahm die Fähigkeit zur Bildung von Sprossen schnell ab.

4. Stücke von 1 cm Länge mit normal ausgebildeter Knospe waren nach 6 Tagen ununterbrochenem Aufenthalt bei 56% relativer Feuchte nur noch zu 5% entwicklungsfähig. Bei gleichlangem Aufenthalt unter 66% relativer Feuchte trieben noch 25% aller Knospen aus, während bei 75% oder 88% relativer Feuchte keine Schädigung erkennbar war.

5. Dünne Rhizomteile waren empfindlicher gegen trockene Luft als extrem dicke, kurze Stücke etwas empfindlicher als längere.

6. Wechsel zwischen Trockenheit und Feuchte im Tag‐Nacht‐Rhythmus hatte eine wesentlich geringere Minderung der Entwicklungsfähigkeit zur Folge als eine ununterbrochene Einwirkung der Trockenheit von etwa gleicher Gesamtdauer.

7. Bei extremer Trockenheit wurde die Wirkung durch eine kräftige Luftbewegung (bis zu 5,5 m/sec) wesentlich verstärkt.

8. Die praktischen Folgerungen aus den Versuchen werden diskutiert.

The reaction of rhizomes of Agropyron repens to dry air
CONTROL OF WEEDS IN MARROWSTEM KALE BY EPTC AND SOME OTHER HERBICIDES
Authors: HAMMERTON J. L.
Published: July 2006

Summary. Two experiments on chemical weed control in marrowstem kale are reported. In the first of these three herbicides applied before sowing were compared; in the second experiment four herbicides were studied, one applied before sowing and the others applied after emergence. Of all the herbicides examined, EPTC, applied before sowing and incorporated into the seedbed, was the most satisfactory in terms of both weed control and yield of kale. Neither endothal + propham nor dinoseb + TCA proved satisfactory as pre‐sowing treatments. The three herbicides applied post‐emergence (all methylmercapto triazines) were ineffective for the control of Polygonum spp. and Poa annua, although fairly effective against Stellaria media and Chenopodium album. They caused considerable damage to the crop and reduced yields by at least 25%.

Le désherbage du chou moellier par l'EPTC et quelques autres herbicides
CHEMICAL INHIBITION OF CROP GERMINATION BY WEED SEEDS AND THE NATURE OF INHIBITION BY ABUTILON THEOPHRASTI
Authors: GRESSEL J. B. , HOLM L. G.
Published: July 2006

Summary. Aqueous extracts of the ground seeds of thirteen weed species were assayed for their ability to inhibit the germination on filler paper of eight crop species. All of the extracts delayed germination of at least some of the crop species. Germination of some crop species was delayed when the crop seeds were surrounded by weed seeds on filter paper, The seeds of Abutilon theophrasti were inhibitory to tomato (Lycopersicum esculentum) germinated in sterile and non‐sterile soil in the laboratory. The inhibition of germination was apparent under conditions which excluded light, water and minerals as factors in the competition. Chemical studies indicated that the inhibition by Abutilon seeds was due to free amino acids emanating from the seeds.

Inhibition chimique de la germination de plantes cultivées par des semences de mauvaises herbes et nature de l'inhibition par Abutilon theophrasti
RESPONSE OF SPRING WHEAT TO THE APPLICATION OF 2,4‐D AT VARIOUS GROWTH STAGES*
Authors: PINTHUS M. J. , NATOWITZ Y.
Published: July 2006

Summary. Two Triticum aestivum and two T. durum varieties were sprayed at five different growth stages with 0–5 and 1 kg/ha 2,4‐D on the same day. The most sensitive stage was that of spike initiation, the most resistant phase followed the completion of spike differentiation, and plants close to caring were again very sensitive. Grain yield reductions of up to 19% with the low dose and 34% with the high dose were observed. The yield reductions at all growth stages were mainly due to a decrease in the number of kernels per spikelet. Application of 2,4‐D during tillering also reduced the numbers of spikes per plant and spikelets per spike. Malformations of the spikes occurred in some plants of T. aestivum treated at spike initiation, but these spikes did not differ in grain yield from normal spikes from equally treated plants.
GENETIC VARIATION IN SIMAZINE RESISTANCE IN WHEAT, RAPE AND MUSTARD
Authors: KARIM A. , BRADSHAW A. D.
Published: July 2006

Summary. The resistance to simazine of a range of varieties of wheat (Triticum aestivim L.), rape (Brassica napus L.) and mustard (Sinapis alba L.) was assessed in glasshouse tests Varietal differences in survival and final weight of survivors were found in all three crops Variability m the time for which individual plants survived was greatest in the two out‐breeding crops, rape and mustard. The 1 % of mustard plants that survived 10 oz/a csimazine were allowed to produce seed in a polycross. These progenies showed a very marked increase m resistance over the unselected controls.

There is thus appreciable genetic variation in resistance to simazine both within and between varieties. This is readily available for selection, and could he valuable in extending the selectivity of herbicides.

Variation génétique de la resistance á la simazine chez le blé, le colza et la moutarde
ROOTING CHARACTERISTICS AND VARIETAL TOLERANCE OF SUGARCANE TO DIURON
Authors: And SHENG Y. PENG , YEH HOUNG J.
Published: July 2006

Summary. The relative susceptibility of six commercial sugarcane varieties to diuron previously described was confirmed in a second similar experiment. A significant correlation was found between the susceptibility of these varieties to 10 kg/ha diuron and their rooting characteristics. The more susceptible varieties were found to produce larger sett‐roots and smaller shoot‐roots, both of which also tended to be more easily injured by diuron. The root injury appeared as‘burnt’root tips resulting from contact with the layer of soil treated by the herbicide. The roots of tolerant varieties seemed to be immune to such injury and continued growing after penetrating the contaminated soil layers. Retarded plant growth appeared to result from the root injury.

Uptake of diuron through shoot‐roots of the susceptible variety F 156 resulted in 68·5% growth retardation. This damage was reduced by 15·5% if the plants were allowed to develop sett‐roots from two‐bud cutting. Death of the plant resulted when both root systems received the same dose of herbicide.
THE NATURE AND CONSEQUENCE OF INTERFERENCE BYALOPECURUS MYOSUROIDESHUDS. ON THE GROWTH OF WINTER WHEAT
Authors: NAYLOR ROBERT E. L.
Published: July 2006

Summary.In a field experiment with different densities ofAlopecurus myosuroides, 10 plants/m2caused no significant reduction in total dry weight of winter wheat at harvest. When autumn‐ or spring‐germinated plants at 100/m2remained until harvest, crop weight was reduced by about 30%. A study of root‐zone competition betweenA. myosuroidesand winter wheat in the glasshouse showed that suppression of the weed by the crop was greater at high nitrogen levels; the practical implications of this are discussed.

La nature de l'interférence d'Alopecurus myosuroïdesHuds. sur la croissance du blé d'hiver, et ses conséquences
Differences in the tolerance of metribuzin by varieties of soybeans
Authors: HARDCASTLE W. S.
Published: July 2006

Summary: Résumé: Zusammenfassung

Metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazin‐5(4/f)‐one] has shown promise for weed control in Glycine max (L.) Merr. (soybean), but at rates effective for preemergence weed control soybean tolerance has been narrow and field observations indicated that varieties of soybeans differed in their tolerance.

Treatments of 0.0,0.56,1,12 and 1,68 kg/ha an location in the Coastal Plain, Piedmont, and Limestone Valley‐area of Georgia indicated that the soybean variety ‘Coker 102’ was Meterially more susceptible to metribuzin injury than were ‘Hardee’, ‘Bragg’, ‘Bienville’, ‘Hampton 266 A’, or ‘Coker 318’. The injury caused smaller soybean stands, heights, and yields. These results confirmed previous observations from field trials using this herbicide.

Différences de sensibilités variétales chez le soja vis‐à‐vis de la métribuzine

La métribuzine [4‐amino‐6‐tert‐butyl‐3‐(méthylthio)‐as‐triazine‐5(4H)‐one] a donné des résultats prometteurs pour le Désherbage du soja Glycine max (L.) Merr. Aux doses efficacies pour le désherbage en prélevée, la résistance du soja a étéétroite et les observations faites au champ ont mis en évidence des difféarences de sensibilité entre les variétés de soja.

Des traitements à raison de 0,0, 0,56, 1,12 et 1,68 kg/ha à des emplacements situfés dans les régions suivantes: Coastal Plain, Piedmont et Limestone Valley, dans l'éatat de Georgie, ont montré que la variété de soja ‘Coker 102’était notablement plus sensible à la métribuzine que les varietés ‘Hardee’, ‘Bragg’, ‘Bienville’, ‘Hampton 266 A’ ou ‘Cocker 318′. Les dégâts se traduisirent par une réduction de Ia vigueur, de lataille et du rendement. Ces résultats confirment les observations antérieures dans des essais au cham pavec cet herbicide.

Unterschiede in der Toleranz von Metribuzin gegenüber Sojabohnensorten

[4‐Amino‐6‐tert.‐butyl‐3‐(methylthio)‐as‐triazin‐5(4H)‐one] ist ein aussichtsreiches Herbizid für die Unkrautbekämpfung in Glycine max. (L.) Merr. (Sojabohne). Bei wirksamen Aufwandraengen im Vorauflaufverfahren war die Sojabohnentoleranz wenig ausgeprägt und Feldbeobachtungen zeigten, dass Sojabohnensorten unterschiedlich tolerant sind.

Behandlungen mit 0,0, 0,56, 1,12 und 1,68 kg/ha an Standorten in der Coastal Plain, Piedmont und der Limestone Valley‐Gegend in Georgia zeigten, dass die Sojabohnensorte ‘Coker 102’ erheblich empfindlicher gegenuber Metribuzinschaden war als ‘Hardee’, ‘Bragg’, ‘Bleinville’, ‘Hampton 266 A’ oder ‘Coker 318′. Der Schaden äusserte sich in geringeren Bestandesdichten, Pflanzenhöhen und niedrigeren Erträgen. Diese Ergebnisse bestätigen die schon früher mit diesem Herbizid gemachten Beobachtungen in Freilandversuchen.
Control of weeds with UHF electromagnetic fields
Authors: WAYLAND J. , MERKLE M. , DAVIS F. , MENGES R. M. , ROBINSON R.
Published: July 2006

Summary: Résumé: Zusammenfassung

Ultra‐high frequency (UHF) etectromagnetic energy (2450±20 MHz) was applied for the pre‐emergent and post‐emergent control of weeds. Pre‐emergent tests in the field indicated that energy levels above 70 J/cm2 were required for consistent control. There was no consistent selectivity between broad‐leaved weeds and grasses when pre‐emergent applications were made. Post‐emergent tests indicated that broadleaved weeds were more susceptible than grasses to the UHF energy. Established plants were more susceptible than were seedings of the same species.

Lutte contre les mauvaises herbes avec des champs magnétiques a ultra hautes fréquences

Une énergie électromagnétique à ultra haute fréquence (UHF) (2450±20 MhZ.) a été utilisée pour la lutte contre les mauvaises herbcs en pre et en post levee. Des essais au champ en prélevée out montré que des niveaux d'énergie supérieurs à 70 joules:cm2étaient nécessaires pour obtenir des résultats satisfaisants. II n'a pas été constaté de sélectivité entre plantes à feuilles larges et graminées vis‐à‐vis des traitements en prélevée, Les essais en posilevée onl montré que les mauvaises herbes à feuilles larges étaient plus sensibles que les graminées. à I'énergie UHF. Les plantes établies se sont révelées plus sensibles que les plantules des mêmes espéces.

Unkrautbekämpfung mit elektromagnetischen UHF‐Feldern

Elektromagnetische Energie im Bereich der Ultrahochfrequenzen (UHF; 2450±20 MHz) wurde zur Unkrautbekämpfung im Vor‐ und Nachauflaufverfahren eingeseizt. Feldversuche im Vorauflauf zeigten, dass für eine brauchbare Bekämpfung, Energien von über 70 joules/cm2 nötig waren. Die Anwendung im Vorauflauf war zwischen dikotylen Unkräutern und Gräsern nicht selektiv. Versuche im Nachauflaufverfahren zeigten, dass dikotyle Unkräuter gegenüber der UHF‐Energie empfindlicher waren als die Gräser. Von der gleichen Species waren grössere Pflanzen jeweils empfindlicher als die Keimpflanzen.
Ecology and control of blackberry (Rubus fruticosus L. agg.) V. Control by picloram granules*
Authors: AMOK R. L.
Published: July 2006

Summary: Résumé: Zusammenfassung

The response of blackberry (Rubus fruticosus L. agg.) thickets and of pastures to picloram granules applied in winter or spring was studied in Victoria, Australia.

A dose of 10–12 kg ha−1 killed the thickets provided that the litter was no more than 2–3 cm deep. 5·6 kg ha−1 was equally effective if the top growth was mown before the granules were applied. The reason for the greater effectiveness of picloram on mown thickets is not clear, but may involve reduced carbohydrate reserves, reduced dilution of picloram in the roots, or greater accumulation of picloram at sites of meristematic activity.

The value of picloram granules for the control of blackberry is discussed in terms of soil residues and cost.

Ecologie et destruction des ronces (Rubus fruticosus L. agg.) V. Lutte au moyen du piclorame granulé.

La réaction des ronces à l'état de buissons ou dans les pâtures, après traitement au piclorame granulé, appliqué en hiver ou au printemps, a étéétudiée dans l'Etat de Victoria, Australie.

Une dose de 10 à 12 kg/ha a détruit les buissons à condition que la litière n'ait pas plus de 2 à 3 cm de profondeur. La dose de 5,6 kg/ha a étéégalement efficace, à condition que les tiges aient été fauchées avant que les granulés n'aient étéépandus. La raison de la meilleure efficacité du piclorame sur les plantes fauchées n'est pas claire, mais il se peut que la fauchaison provoque la réduction des réserves en hydrates de carbone, réduise la dilution du piclorame dans les racines ou provoque une accumulation plus forte de piclorame dans les sites d'activité méristématiques.

La valeur des granules de piclorame pour la lutte contre les ronces est discutée en tenant compte desrésidus dans le sol et du prix de revient.

Ökologie und Bekämpfung der Brombeere (Rubus fruticosus L. agg.) V. Bekämpfung mit Picloram‐Granulat

In Victoria (Australien), wurde im Winter und im Frühjahr Picloram‐Granulat in Brombeerdickichten und auf Weideland angewendet, um die Wirkung auf die Brombeere (Rubus fruticosus L. agg.) zu untersuchen.

10–12 kg ha−1 brachten die Dickichte zum Absterben, vorausgesetzt, dass die Streu nicht stärker als 2–3 cm war. Die gleiche Wirkung wurde mit 5.6 kg ha−1 erzielt, wenn vor der Granulatanwendung die Spitzen der Pflanzen abgemáht wurden. Die Ursache für die bessere Wirkung von Picloram bei den derartig gemähten Dickichten ist unklar. Möglicherweise ist diese Wirkung im Zusammenhang mit verringerten Kohlenhydratrcserven, einer weniger starken Verdüinnung von Picloram in den Wurzeln, oder einer starkeren Anreicher‐ung des Herbizids an Orten meristematischer Aktivität zu sehen.

Die Brauchbarkeit von Picloram‐Granular für die Brom‐beerbekämpfung wird unter dem Gesichtspunkt der Rückstände im Boden und der Kosten besprochen.
Cinétique de dissolution dans l'eau de l'atrazine, de la propazine et de la simazine
Authors: CALVET R. , TERCE M. , LERENARD J.
Published: July 2006

La solubitilé et les cinétiques de dissolution dans l'eau de I'atrazine, de la propazine et de la simazine ont étéétudiées à différentes températures. L'ordre apparent des réactions de dissolution est de I pour l'atrazine et la propazine, 2 pour la simazine. La solubilité et les constantes de vitesse sont des fonctions croissantes de la température. Les énergies d'activation de la vitesse de dissolution sont de l'ordre de 4,1 à 4,8 kcal mole‐1. Elles correspondent à une diminution de 30% ilti temps de demie‐réaction pour une augmentation de température de 10°C. II apparaît ainsi que l'eflicacité d'un traitement peut dépendre en partie de l'importanee des pluies et de la température du sol.
A novel approach to Striga and Orobanche control using synthetic germination stimulants
Authors: JOHNSON A. W. , ROSEBERY G. , PARKER C.
Published: July 2006

A series of synthetic germination stimulants for the plant parasites Striga and Orobanche has been prepared. These compounds, analogues of the natural Striga germination stimulant, strigol (I), (Cook et al., 1966, 1972) cause signiticant germination of Striga hermonthica (Del.) Benth. seed at concentrations as low as 10−9 M, and an even greater activity against species of Orobanche has been demonstrated. Initial outdoor box trials of the compounds against Striga asiatica (L.) O. Ktze. in Hyderabad, India, have shown a reduction of up to 65% of the seed after a single treatment of the soil 6 weeks before the planting of the sorghum host.
The influence of temperature and photoperiod on growth and development of Parthenium hysterophorus L.
Authors: WILLIAMS J. D. , GROVES R. H.
Published: July 2006

Germination, growth and flowering were investigated in Parthenium hysterophoms (Asteraceae), a species introduced to Australia and at present occurring as a weed in central Queensland. Combinations of day/night temperature regimes from 15/4 to 36/31 and day length of 10, 13 and 16 h in controlled conditions were examined to find the effects of any environmental restraints to growth and development. Results showed that individuals are able to germinate, grow and flower over a wide range of temperatures and photoperiods and established plants can survive at least one mild frost of — 2.

We conclude that the potential distribution of P. hyslerophorus in Australia is much wider than at present. Future distribution of the species may be limited seasonally by the inability of seed to germinate in soils of low water potential and by the inability of seedlings to establish and grow at low light intensities.
Effect of ammonium sulphate and other additives upon the phytotoxicity of glyphosate to Agropyron repens (L.) Beauv
Authors: TURNER D. J. , LOADER M. P. C.
Published: July 2006

In several pot and field experiments additions of 1–10% w/v ammonium sulphate and/or 0.1–2.5% w/v surfactant increased the phytotoxicity to A. repens of sprays containing 0.2–0.5 kg/ha glyphosate. There were similar results with technical glyphosate‐isopropylamine salt and formulated ‘Roundup’. Higher ammonium sulphate concentrations were sometimes antagonistic. Additions of ammonium sulphate without surfactant generally had less effect on phytotoxicity. While several surfactants increased glyphosate activity the order of effectiveness of these products varied according to whether or not ammonium sulphate was also present. When used alone, relatively hydrophilic non‐ionic or cationic products had more effect. In mixtures with ammonium sulphate, however more lipophilic surfactants gave superior results. Ammonium sulphate (5%) with a lipophilic cationic surfactant (0.5% Ethomeen C12) enhanced the effects of very low volume controlled‐drop applications as well as conventional medium volume sprays. In a field trial 0.25 kg/ha glyphosate applied with those additives in 20 l/ha of spray had as much effect on bud viability as l kg/ha applied conventionally.
Weed control in irrigated dry seeded rice
Authors: GHOBRIAL GEORGE I.
Published: July 2006

Large losses in grain yields due to weed competition were found in studies conducted in irrigated dry seeded rice at Gezira Research Station, Sudan. These losses could exceed 50%. Weed competition lowered panicle number per unit area by 37%, number of filled grains per panicle by 13%, and weight of 1000 grains by 4%. Tillering was the critical growth phase most affected by weed competition.

Grain yields were increased as number of hand weedings increased. The best yield (4.1 t/ha) was obtained from 3–4 weedings carried out at 15, 30, 45 and 60 days after rice emergence.

Oxadiazon (0.5 kg/ha) gave good residual weed control of the dominant weed species, Phyllanthus niruri L., Leucas urticifolia L., Heliotropium F.W.Andr. and Echinochloa colona (L.) Link, for 6–7 weeks. The combination with continuous flooding from 6 weeks after rice emergence gave excellent weed control during the entire season, and comparable or even better yields than frequently weeded rice.
Joint action of root‐absorbed mixtures of DPX‐4189* and linuron in Sinapis alba L. and barley
Authors: STREIBIG J.C.
Published: July 2006

The joint action of DPX‐4189* (2 chloro‐N‐[(4‐methoxy‐6‐methyl‐1, 3, 5‐triazin‐2‐yl)‐aminocarbonyl] benzenesulfonamide) and linuron (N‐[3, 4‐dichlorophenyl]‐N‐methoxy‐N‐methylurea) mixtures, applied in fixed ratios of 1:15 and 1:30, was assessed using water culture experiments in growth chambers.

The dose‐response curves of DPX‐4189 were fiat compared with these of linuron. At Gr50‐level (the dose required to reduce dry matter by 50% relative to the untreated control), DPX‐4189 was 12‐fold more potent in Sinapis alba than was linuron, whereas the potencies of the two compounds were almost similar in barley. The selectivity indices (Gr80[barley]/Gr20[S. alba]) of DPX‐4189 and linuron were 3.1 and 1.8.

In both species the mixtures were less active than expected from an additive dose model, and the detracted efficacy of the mixtures was of almost similar magnitude. The results indicated that if S. alba is regarded a weed, the loss of bioactivity of the mixtures may be compensated by some increase in dose rate without injuring the barley crop.
Improvement of carpet grass (Axonopus affinis Chase) pasture by fertilization and oversowing with the aid of selective herbicides
Authors: MARTIN R. J.
Published: July 2006

An experiment was done to determine the effect of spring and autumn application of asulam and dalapon, nitrogen fertilizer and oversown white clover (Trifolium repens L.) on the productivity of subtropical pasture dominated by carpet grass (Axonopus affinis Chase). Assessments were made of pasture yield, botanical composition, weed invasion and recolonization by pasture species during the 12‐month period following herbicide application. Both herbicides decreased the yield of carpet grass and increased that of the more productive paspalum (Paspalum dilatatum Poir.) except after autumn application when the yield of paspalum was greatly reduced by dalapon. White clover became established only on plots treated with herbicide and only after autumn application. Clover yields were greatest on plots treated with dalapon. Asulam was considered to be the most suitable herbicide for altering the balance between carpet grass and paspalum because dalapon initially reduced paspalum yield after autumn application and delayed recovery of total pasture. In addition, dalapon permitted greater invasion by broadleaf weeds. This work showed that herbicides have a potential role for speeding up botanical changes in unproductive carpet grass pasture and further refinement of the technique might provide a useful tool for increasing pasture productivity.
Field emergence and temperature requirements for germination in Solanum sarrachoides Sendt.
Authors: ROBERTS H. A. , BODDRELL JUNE E.
Published: July 2006

Emergence of Solanum sarrachoides began in late April, reached a peak in May or June and ceased in September. This pattern closely resembled that for S. nigrum L., whereas almost all seedlings of S. dulcamara L. emerged in April. Fresh seeds of S. sarrachoides were dormant but developed a capacity for germination at 25 and 30°C and at alternating (16 h low/8 h high) temperatures of 4/25, 10/25, 10/30 and 20/30°C when stored dry. kept moist at 4°C or buried in the field. Buried seeds also became capable of germinating at 10. 15 and 20°C and the temperature range for germination was widest during April‐June. Induced dormancy developed during August and the range narrowed. The consistent seasonal emergence pattern appears to be associated with cyclic changes in the dormancy status of buried seeds.
A second survey of cereal weeds in central southern England
Authors: CHANCELLOR R.J. , FROUD‐WILLIAMS R.J.
Published: July 2006

A survey of grass weeds of cereals in central southern England made in 1981 was repeated in 1982 between 28 June and 23 July. Dicotyledonous weeds were also assessed in 1982. A total of 1021 fields were surveyed, 702 in winter wheat. 198 in winter barley and 121 in spring barley. A total of twenty‐four grass weeds were found and their levels of infestation were scored. The most frequently found grass weeds were the same as in 1981. In all cereals combined, these were Elymus (Agropyron) repens in 35% of fields, Avena fatua in 32%, Alopecurus myosuroides in 26% and Poa trivialis in 24%. Sixty‐three species of dicotyledonous weeds were recorded and of these, eighteen species occurred in 2% or more of fields. The eight most frequent were Viola arvensis, Galium aparine, Stellaria media, Myosotis arvensis, Polygonum aviculare, Convolvulus arvensis, Bilderdykia (Polygonum) convolvulus and Lamium purpureum. Most species were fairly uniform in distribution, but Galium aparine, Convolvulus arvensis and Cirsium arvense were most frequent in the east while Viola arvensis was least frequent there. The cereals varied in weediness, 32% of winter barley, 23% of spring barley and only 7% of winter wheat fields had no weeds recorded.
Activity of extracts from Euphorbia species on the germination of Striga species
Authors: IBRAHIM N. E. , BABIKER A. G. T. , EDWARDS W. G. , PARKER C.
Published: July 2006

Aqueous extracts of fifteen Euphorbia species induced germination of Striga hermonthica (Del.) Benth. seeds to varying extents. Extracts from E. supina Raf., E. pilulifera Jacq., E. acalyphoides Hochst. ex. Boiss, E. prunifolia (Jacq.) Hort. Schoent., E. hirta L., E. aegyptiaca Boiss, E. splendens Boj., and E. granulata Forsk, were the most active. Extracts from E. acalyphoides and E. pilulifera were inhibitory at high concentrations. Undiluted extracts from E. pilulifera, E. aegyptiaca and E. hirta induced haustorial initiation. The stimulatory substance(s) were widely distributed in plants of E. aegyptiaca. Extracts from E. aegyptiaca also stimulated seed germination and haustorial initiation in a range of Striga species and strains.
Influence of soil moisture on isoproturon activity against Alopecurus myosuroides
Authors: BLAIR A.M.
Published: July 2006

Alopecurus myosuroides Huds. (blackgrass) in sandy loam soil in pots was treated at the three‐leaf stage with formulated isoproturon. Damage to plants resulted mainly from herbicide entry via the soil. When the soil moisture levels were maintained close to 50, 100 and 150% of field capacity (FC) throughout the experiment damage increased with the amount of water in the soil. After spraying plants raised at field capacity, change to 150 or 50% FC resulted in more and less damage respectively. Water applied to the soil surface compared with sub‐irrigation caused more damage. A delay of up to 21 days between spraying plants in soil at field capacity and surface watering did not reduce damage provided the time interval between the onset of surface watering and assessment remained constant. A delay of 7 days between spraying isoproturon onto plants in dry soil (50% FC) and increasing the moisture to field capacity by surface watering decreased the damage to A. myosuroides. These results are discussed with reference to the soil moisture distribution in soil columns and rainfall patterns under field conditions.
Studies on the site of uptake by plants of chlortoluron and terbutryne
Authors: ADDALA M. S. A. , HANCE R. J. , DRENNAN D. S.
Published: July 2006

Experiments were done to observe the pattern of early root development of radish (Raphanus raphatnistrum L.) and perennial ryegrass (Lolium perenne L.), the mobility of chlortoluron following application to the soil surface, the effect of protecting the subterranean shoots of four plant species on their response to chlortoluron and terbutryne and the relative quantities of 14C‐labelled chlortoluron taken up by radish and Avenu fatua from root and shoot zone exposure. Both chlortoluron and terbutryne appear to be able to enter the plants examined, Alopecurus myosuroides, Stellaria media, perennial ryegrass and radish, through roots and shoots. It is suggested that shoot uptake is relatively more important for plants like perennial ryegrass than for those whose roots develop more quickly and invade the soil above the seed, such as radish. The quantities of radioactive chlortoluron taken up from soil containing 400 ng g−1 showed that less than 3 ng per plant could reduce A. fatua fresh weight by 17–40% while over 30 ng per plans had little effect on radish. By comparison 2 kg ha−1 chlortoluron applied to the soil surface of pots which were sub‐irrigated for 3 weeks gave a concentration of 170 ng g−1 in the layer of soil 10–12 mm from the surface. It is suggested that for shallow germinating species with herbicides of physical and phytotoxic properties similar to chlortoluron, the solvent action of rainfall, together with diffusion, is enough to allow the transport of toxic quantities to the target plant although any leaching action is likely to increase activity.
Selective regulation of germination and growth of annual weeds by crop residues
Authors: PURVIS C. E. , JESSOP R. S. , LOVETT J. V.
Published: July 2006

Residues from mature, harvested crops of sorghum (Sorghum bicolor Moench.), sunflower (Helianthus annuus L.), oilseed rape (Brassica napus L.), wheat (Triticum aestivum L.) and field pea (Pisum sativum L.), exhibited selective effects on weed germination and growth under field conditions. Weed species in the study included Avena fatua L., Avena sterilis ssp. ludoviciana (Durieu) Nyman, Echinochloa crus‐galli (L.) Beauv., Phalaris aquatica L., Phalaris paradoxa L., Lolium perenne L., Vulpia myuros (L.) Gmel., Hibiscus trionum L., Polygonum aviculare L., Bilderdykia convolvulus (L.) Dumort. and Lamium amplexicaule L. All crop residues tested, and in particular wheat and pea residues, promoted the germination and growth of A. fatua and A sterilis ssp. ludoviciana. Other grass weeds, however, were inhibited by the presence of crop residue, the extent of inhibition being dependent on residue type. Germination response of dicotyledonous weed species was also a function of residue type, H. trionum numbers were significantly higher in plots where oilseed rape, sorghum or sunflower residue had been incorporated, while L. amplexicaule was inhibited by these residue types and stimulated by pea and wheat residues.
Long‐ and short‐term effects of vapour of the herbicide 2,4‐D butyl on the growth of tomato plants
Authors: BREEZE V. G. , WEST C. J.
Published: July 2006

An airflow system has been used to expose tomato plants to a range of concentrations of vapour of the herbicide 2,4‐D butyl, from 5 to 50 ng l−1. Experiments carried out at an air temperature of 20°C indicate that only short periods (less than 2.5 h) are required to produce symptoms of phytotoxicity at concentrations less than 5 ng l−1, or approximately 2.5% of the saturated vapour pressure of the herbicide. A 5‐h period of exposure to approximately 5 ng l−1 reduced the dry weight and dry matter content of the tomato plants after 7 weeks by 18% and 9%, respectively, compared with the control. Phytotoxicity symptoms were shown by the plants in proportion to the vapour concentration during the period of exposure to herbicide. Rates of photosynthesis of treated plants had begun to decline within an hour of the commencement of exposure, slightly after leaf movement was first observed.
Metribuzin metabolism as the basis for tolerance in barley (Hordeum vulgare L.)*
Authors: GAWRONSKI S. W. , HADERLIE L. C. , STARK J. C.
Published: July 2006

Metabolism of 14C‐5 (ring)‐metribuzin was studied in Steptoe (tolerant) and Morex (susceptible) barley (Hordeum vulgare L.) cultivars, 1, 4, and 8 days following a single application to roots. Both cultivars contained similar ether‐soluble metribuzin metabolites and five water‐soluble metabolites. Water‐soluble compounds increased from 12 to 53% of the total 14C recovered for Steptoe and 5–17% for Morex between 1 day and 8 days, respectively, whereas the percentage of ether‐soluble metabolites decreased. Ninhydrin reacting compounds were the major water‐soluble metabolites in the leaf blades 8 days after treatment. On a d.p.m. mg−1 dry weight basis, Steptoe leaves had five times more water‐soluble material than Morex leaves and half the quantity of ether‐soluble compounds. Metribuzin comprised 83 and 89% of the ether‐soluble compounds in leaves of Morex and Steptoe, respectively, at 8 days. Terminal radioactivity comprised between 19% and 26% of total radioactivity for both cultivars as early as 1 day after application, with little change over 8 days. Rapid metabolism of metribuzin to non‐phytotoxic water‐soluble conjugates and terminal residues was the major mechanism responsible for the differential tolerance between these two barley cultivars.