bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photosynthetic parameters in glyphosate‐treated sugarbeet (Beta vulgaris L.)
Authors: MADSEN K. H. , HEITHOLT J. J. , DUKE S. O. , SMEDA R. J. , STREIBIG J. C. 
Published: July 2006

SummaryVariable fluorescence and carbon dioxide exchange rate (CER) were measured in intact leaves of glyphosate‐treated sugarbeet plants, to investigate rapid effects on photosynthesis. In one experiment, a significant effect on variable fluorescence and CER was found within 8 h after herbicide application. The effect on stomatal conductance was not significant. In a second experiment, the effects of light or dark conditions during herbicide application and 24 h later were evaluated. Under light conditions glyphosate significantly reduced variable fluorescence after 4 h. However under initial conditions of 24 h darkness, followed by alternating 8 h light/8 h dark, the effect was not significant until 44 h after treatment, by which time the plants had received several hours of light. The eflect on variable fluorescence 8 h after herbidde application correlated positively with plant survival 7 days later.
Profils écologiques et liaisons interspécifiques. Deux approches complémentaires appliquées à l'étude des groupements de mauvaises herbes des cultures du Saïs (Maroc central)
Authors: LOUDYI M. C. , GODRON M. , ELKHYARI D. 
Published: July 2006

Résumé: SummaryL'étude présentée est basée sur les données fournies par l'exploitation de 277 relevés réalisés dans les cultures du Saïs entre 1977 et 1987. Les relevés ont été soumis parallélement à deux méthodes d'analyse: la méthode des profils écologiques et l'analyse statistique des liaisons interspécifiques.Vingt groupes coenologiques de mauvaises herbes ont été mis en évidence par l'analyse statistique des liaisons interspécifiques. Deux groupes, choisis parmi les 20, sont analysés dans cette étude.Les groupes coenologiques sont interprétés en faisant appel à la lecture des profils écologiques des espéces. L'utilisation conjointe des deux méthodes montre qu'elles sont adaptées à l'étude du milieu cultivé et complémentaires quant à leurs apports, L'interprétation de ces groupes apporte des informations intéressantes concernant la sensibilité des mauvaises herbes aux descripteurs du milieu et la valeur indicatrice des espèces.En dépit d'une certaine concordance des résultats obtenus par chacune des deux approches, l'étude montre que la méthode analytique des profils écologiques permet une analyse plus détaillée du comportement des mauvaises herbes. Elle offre, en effet, la possibilité de nuancer le comportement de certaines espèces à l'intérieur d'un groupe coenologique donné et de détecter des tendances que l'analyse des liaisons interspéciques ne permet pas, à elle seule, de percevoir. Ecological profiles and interspecific associations: two complementary approaches to the study of weed associations in arable land in the region of Saïs (Central Morocco) This study is based on botanical species data obtained from 277 samples taken from the cropped areas of Saïs, Morocco, between 1977 and 1987. Two types of analysis were done: definition of ‘ecological profiles’, and statistical analysis of interspecific associations. Twenty groups of weeds with highly correlated presence or absence ('coenological groups') were detected by statistical analysis of interspecific links. Two of these groups were selected for more detailed analysis in this study. The results demonstrated that both methods of analysis were well suited to the study of weed associations in cultivated areas, and they provided information about the indicator value of species for environmental variables. Although the methods gave similar results, that of ecological profiling allowed a more detailed analysis of weed behaviour as it permitted small variations in behaviour of species within similar coenological groups to be distinguished.
Non‐enzymatic conjugation of fenoxaprop‐ethyl with glutathione and cysteine in several grass species
Authors: TAL J. A. , HALL J. C. , STEPHENSON G. R. 
Published: July 2006

SummaryLaboratory studies have shown that the amounts of glutathione (GSH) and cysteine are higher in grass species that are moderately tolerant, such as wheat (Triticum aestivum L., cv. Fredrick), and moderately susceptible, such as barley (Hor deum vitlgare L., cv. Legér) and triticale (cv. OAC Trillium), to fenoxaprop‐ethyl (FE) than in species that are very susceptible to the her bicide, such as oat (Avena saliva L., cv. OAC Woodstock), wild oat (Avena fatua L.), yellow foxtail (Setaria glanca (L.) Bcauv.), large crab grass (Digitaria sanguinalis (L.) Scop.) and bar nyard grass (Echinochloa crus‐galli (L.) P.B.). The safener, fenchlorazole‐ethyl (FCE) was found to increase and decrease, respectively, the amounts of GSH and cysteine in the moderately tolerant and moderately susceptible species but had no effect on the susceptible species. It is sug gested that in the moderately tolerant and moderately susceptible species, especially following FCE treatment, more GSH is available to detoxify the herbicide. Glutathione‐S‐tranferase activity (GST) for FE was found to be very low in all of the species tested. In vitro experiments at physio‐logical pH. demonstrated that FE may conjugate with GSH nonenzymatically. Therefore, it is suggested that nonenzymatic conjugation of fenoxaprop‐ethyl with glutathione may be an important mechanism for tolerance of some grasses to this herbicide.
Impact of drilling date on Apera spica‐venti L. and Alopecurus myosuroides Huds, in winter cereals
Authors: MELANDER B. 
Published: July 2006

SummaryThe impact of drilling date on Apera spica‐venti and Alopecurus myosuroides in winter cereals was investigated in field trials in 1991 and 1992. Two drilling dates were considered with an inter val of 14 to 16 days between dates. Generally, drilling date had an inconsistent effect on weed plant populations in spring, but seedling emerg ence of both species appeared to be delayed at the later drilling compared with the earlier date. This delay may partly explain the reduced com petitive ability of A. myosuroides in wheat in 1991 and 1992 and of A. spica‐venti in wheat in 1991 at the later drilling date. The seed popula tion per plant of both species was lower at the later date in some instances, whereas in others drilling date had no effect. Reduced seed produc tion was mainly caused by a reduction of the number of inflorescences per plant. The poten tial of utilizing drilling dates as a cultural control measure against grass weeds is discussed.
Simulation of the persistence of atrazine in soil at different sites in Portugal
Authors: ROCHA F. , WALKER A. 
Published: July 2006

SummaryThe effects of soil temperature and soil moisture content on the rates of degradation of atrazine, were measured in the laboratory in soils from different sites in Portugal. Persistence of atrazine was measured in the same soils in the field during the spring and summer of 1984, 1985, 1986 and 1987. Weather records from the different sites, measured during the periods of the field experi ments, were used in conjunction with appropriate constants derived from the laboratory data in a computer program to simulate persistence in the field. The model generally overestimated the ob served soil residues, particularly during the first 7–14 days after application. The fit from the model was good from day 14 to the end of the experiments.
A simulation of herbicide use based on weed spatial distribution
Authors: JOHNSON G. A. , MORTENSEN D. A. , MARTIN A. R. 
Published: July 2006

SummaryIntensive field surveys were conducted to deter mine the spatial distribution of composite broad leaf and grass weed seedlings in seven maize and five soybean fields in eastern Nebraska in 1992. Farmer fields where herbicides were applied in a 38‐cm band over 76‐cm spaced rows were chosen for this study. Weed populations were measured in the interrow and in the band‐treated intrarow. Spatial maps constructed for grass or broadleaf weeds revealed that individual species as well as species assemblages are highly aggregated. On average, 30% of the sample area in the 12 fields surveyed was free of broadleaf weeds and 70% free of grass weeds in the interrow area (no her bicide). Where a pre‐emergence herbicide was applied (intrarow), 71% of the sample area was free of broadleaf weeds and 94% free of grass weeds. Increasing the threshold to some value other than zero resulted in a larger field area not requiring a herbicide application. The results of these distribution studies indicate that herbicide use could be substantially reduced if weed dis tribution maps or real‐time plant sensing were available to provide information for intermittent herbicide application systems or refinement of economic thresholds.
Effect of weed position on yield loss in soyabean and a comparison between relative weed cover and other regression models
Authors: BERTI A. , SATTIN M. 
Published: July 2006

SummaryThe importance of the position of weeds with respect to crop rows in the determination of crop yield‐weed density relationships and the usefulness of relative cover (RC) of the weeds as an explanatory variable were studied in soyabean [Glycine max (L.) Merrill] competing with two summer weeds with contrasting canopy structure (Xanthium strumarium L. ssp. italicum and Echinochloa crus‐galli L.). The position of the weeds was of little importance in the relationship between yield loss and weed density. This information is important because published experiments have used different types of weed distribution (e.g. evenly distributed or sown in rows). For both weed species it was possible to obtain a single relationship between yield loss and RC for measurements made from 30 days after crop emergence to soyabean canopy closure. The competitive effect of the weeds appeared to be strictly related to RC, indicating that for weeds growing taller than the crop the main competitive factor may be the shading caused by the leaves of the weeds situated above the crop canopy.
Changes in Pteridium aquilinum growth and phototoxicity following treatments with lime, sulphuric acid, wood ash, glyphosate and ammonium nitrate
Authors: DOLLING A. 
Published: July 2006

SummaryThe comparative effects of lime, sulphuric acid, wood ash, glyphosate and ammonium nitrate on Pteridium aquilinum (L.) Kuhn growth and development were evaluated in a Scots pine (Pinus sylvestris L.) clear‐cut stand in south‐east Sweden over a 4‐year period. P. aquilinum growth was effectively controlled following the application of glyphosate, but the other treatments generally had little effect on growth in terms of shoot density and length. Shoot length was positively related to the number of shoots on plots treated with ammonium nitrate but negatively correlated with the number of P. aquilinum shoots found on wood ash‐treated and control plots. In a bioassay aspen (Populus tremula L.) seedling emergence and pH were significantly lower in humus treated with sulphuric acid, glyphosate, ammonium nitrate and in untreated humus as compared with the humus treated with lime and wood ash. The negative effect of humus on emergence of aspen seedlings may be caused by phytotoxic compounds at a lower pH level. Forest regeneration might be performed with shade‐tolerant species such as Norway spruce (Picea abies (L.) Karst.) planted beneath a thin canopy of trees to prevent the rapid increase of P. aquilinum.
Growth characteristics of spring barley and selected weeds. II. Effect of temperature and irradiance in growth chambers
Authors: SEMB K. 
Published: July 2006

SummaryAs a part of a broader study, two experiments were carried out in growth chambers with three day/night temperature regimes (10/7, 20/14 and 30/21^C) studying growth characteristics of individual seedlings over a four‐week period. Experiment 1 was performed with spring barley (Hordeum vulgare L.), Galeopsis tetrahit L., and Viola Arvensis Murray. Experiment 2, with three irradiance levels at 20/14^C, and one irradiance level at the other temperatures, was performed with spring barley, V. arvensis, Chenopodium album L., Brassica rapa L. sspoleifera (DC.) Metzger, and Stellaria media (L.) Vill. Leaf area, dry weight, relative growth rate, net assimilation rate, and net photosynthetic rate generally showed an optimum at 20/14^C. Increasing irradiance resulted in a decreased specific leaf area. Expressed as fraction of shoot dry weight, green leaves decreased and stems, flowers, and yellow leaves increased with increased time, irradiance, and temperature. At all temperatures, barley, B. rapa and G. tetrahit had the largest dry weights, but at 20/14^C. C album and S. media and at 30/21^C C. album also had large values. Differences in dry weight between species correlated more to morphological features than to assimilation rate.
Modelling the effect of weed‐seed distribution in the soil profile on seedling emergence
Authors: GRUNDY A. C. , MEAD A. , BOND W. 
Published: July 2006

SummaryExperiments to monitor weed seedling emergence from various soil depths were begun in 1989. Recently shed seeds were buried in either narrow bands at a range of depths in the soil or mixed evenly between the soil surface and each of these depths. Total emergence of Stellaria media (L.) Vill., Matricaria spp., Veronica persica Poiret, Veronica arvensis L. and Polygonum aviculare L., declined with increasing depth of burial. A similar pattern was observed for Chenopodium album L. with the exception of emergence from the surface layer. The reduction in emergence with increasing soil depth was greater for seeds in the narrow‐banded treatments than for those in broad layers. A model was developed using the data from the narrow‐banded treatments to predict emergence from distributions over broad layers. Predictions from the model closely agree with the data from the present broad‐layer treatments and those from a similar experiment made in the 1960s. By including the effects of depth of seed burial on seedling emergence, this model could be combined with models that determine the effects of cultivation on seed distribution, and therefore improve precision of predictions of seedling emergence from the seedbank.
Modelling the economics of herbicide treatment in wheat and barley using data on prevented grain yield losses
Authors: BOURDÔT G. W. , SAVILLE D. J. , HURRELL G. A. , DALY M. J. 
Published: July 2006

SummaryLosses in grain yield prevented by controlling weeds were measured in 59 fields of (southern hemisphere) spring‐sown wheat (Triticum aestivum L.) (cv, Otane) and 45 fields of spring‐sown barley (Hordeum vulgare L.) (cv. Corniche) in five consecutive growing seasons from 1988/89 until 1992/93 in the Canterbury region of New Zealand. The losses were measured as the differences in yield between weeded and non‐weeded plots located in randomly positioned pairs in the fields. In the first 2 years, the weeding was by push hoe in‘organically grown crops. For the last 3 years, the fields were under prophylactic herbicide regimens with nonweeded plots created by excluding commercial herbicide applications (made mostly in October for wheat and November for barley) with polyethylene sheets placed temporarily over the plots. For each season the distributions of yield losses were modelled using the normal distribution and probabilities of ‘breaking even’ on herbicide use derived by substituting cumulative probability density functions into a simple break‐even model for herbicide use. The model assumed that herbicide application in the current crop has no flow‐on economic effect for succeeding crops. The mean annual yield losses prevented by herbicide application were positively correlated with September and October rainfall for wheat and bailey respectively. As a consequence, the probabilities of breaking even on herbicide use increased with increasing spring rainfall. Using historical rainfall records, probabilities of breaking even were estimated for each of the 48 years from 1947 to 1994. Averaging over these years, the analysis revealed that at current grain prices prophylactic use of the commonly applied herbicides is likely to be uneconomic in 24% (95% confidence limits 6% and 50%) of fields of average‐yielding Otane wheat and in 26% (95% confidence limits 1% and 91 %) of fields of average‐yielding Corniche barley in Canterbury. It was concluded that there is potential for withholding herbicide treatments without jeopardizing profitability in these crops, particularly in seasons with low spring rainfall.
Responses of Abutilon theophrasti to agricultural management systems
Authors: ZHANG J. , HAMILL A. S. 
Published: July 2006

SummarySeeds of Abutilon theophrasti Medic., collected from plants growing in a continuous maize or soyabean field subjected to herbicide application, cultivation or no weed management for 10 years, differed significantly in their weight and germinability. The differences in mean weight and germinability of the progeny seeds were maintained when the parent plants were grown in a greenhouse under controlled conditions. The offspring of plants with or without previous exposure to atrazine responded similarly to the herbicide in all the measurements of the growth and development of the plants, except blooms. Significant differences between the two groups of plants were mainly observed in the weight and germinability of their seeds. Although plants with or without previous exposure to atrazine usually did not differ significantly in their response to the herbicide in terms of individual traits, they differed both in the amount and pattern of overall response across all traits. The difference in overall response between plants increased with increasing rate of atrazine. It is possible that previous exposure to the herbicide had caused minor variation in a group of inter‐correlated traits or in the strength or pattern of correlation among traits.
Pathogenicity of fungi collected in northern Ghana to Striga hermonthica
Authors: KROSCHEL J. , HUNDT A. , ABBASHER A.A. , SAUERBORM J. 
Published: July 2006

SummaryThirteen fungal species were isolated from diseased plants of Striga hermonthica (Del.) Benth in northern Ghana. The pathogenicity of 12 isolates of the fungal species including Curvularia fallax Boed, Fusarium equiseti (Corda) Sacc., Fusarium equiseti var. bullatum (Sherb.) Wollenw., F. oxysporum Schlecht, F. solani (Mart) Sacc., Macrophonuina phasealina (Tassi) Goidan, and Sclerotium rolfsii (Sacc.) were evaluated against S. hermonthica under controlled environmental conditions. All isolates were pathogenic to S. hermonthica when propagated on wheat (Triticum aestivum L.) grains and incorporated pre‐planting into the soil. However, their virulence differed. Two isolates of F. oxysporum and one isolate of F. solani reduced the emergence of S. hermonthica by 88%, 98%, and 76%, respectively. Sorghum (Sorghum bicolor (L.) Moench) yield was increased by 26% when S. hermonthica was controlled. In contrast, in the control treatment with S. hermonthica no yield could be obtained. The F. oxysporum isolates were not pathogenic on sorghum. Germination tests indicated that the F. oxysporum isolates were highly pathogenic to S. hermonthica seeds. Although the F. solani isolate reduced the emergence of S. hermonthica in the pot experiments, it did not influence germination. This indicates that pathogens may attack different stages in the life cycle of S. hermonthica.
Atrazine soil metabolism in maize fields treated with organic fertilizers
Authors: ROUCHAUD J. , GUSTIN F. , CALLENS D. , BULCKE R. 
Published: July 2006

SummaryThe metabolism of atrazine in soil was studied in two maize fields located in regions with different soil types. Treatments were cow manure or pig slurry (50 tonnes each ha‐1) applied once either in March or in November before sowing, or green manure incorporated in March. Control plots were not treated with organic fertilizers. Atrazine at 0.75 or 1.0 kg a.i. ha‐1 was applied after sowing. In the 0‐12 cm soil layer, the main atrazine metabolites found were deethylatrazine and hydroxyatrazine. Low concentrations of deisopropylatrazine and 6‐chloro‐1, 3, 5‐triazine‐2, 4‐diamine were also observed. During the 4 months after sowing, the organic fertilizers decreased the rate of atrazine degradation, but subsequently there were no differences between treated and control plots. At harvest, the concentrations of atrazine and its metabolites were very low and similar in all plots. The organic fertilizers thus did not cause atrazine metabolites to accumulate in soil. In addition, atrazine and its metabolites were never detected below 12 cm in any of the plots.
The influence of crop rotation and soil tillage on seed population dynamics of A vena sterilis ssp. ludoviciana
Authors: NAVARRETE L. , QUINTANILLA C. FERNANDEZ 
Published: July 2006

SummaryThe dynamics of seed populations of Avena sterilis ssp. ludoviciana (Durieu) Nyman in plots maintained under different crop rotations and tillage systems was studied over a 5‐year period. The seed reserves buried in the soil were practically depleted during this period by using any of the three cropping systems evaluated. No significant differences were found between using a continuous barley rotation with annual application of herbicides and using a barley:fallow rotation with herbicides applied only as needed. The decline in seed populations was not affected by the tiliage system used during the fallow period (ploughing or no tillage). The tillage practices used in the various treatments, combined with the variable seed output from each treatment, resulted in different vertical distribution of the seeds in the soil profile. Shallow cultivation resulted in an accumulation of seeds in the upper soil layers; in contrast, a large proportion of the seeds were buried and maintained below 15 cm in the ploughed treatments. Although the seed distribution patterns produced by the various tillage systems had an effect on seedling recruitment, the largest changes in this parameter were associated with the different cropping sequences. Four times more seedlings were recruited in years under barley cropping than in those under fallow.
Relationships of the macrobenthos of Moreton Bay to prawns and to abiotic factors
Authors: STEPHENSON W. 
Published: July 2006

AbstractRelationships are established between flux measures in macrobenthos and climatic variables, and between these measures and certain estimates of the catches of penaeid prawns. Cycles in flux do not appear to reflect inherent annual rhythms; positive flux (overall recruitment rates) show strong positive correlations with temperatures of seven months previously; negative flux (overall depletion rates) show strong positive correlations with prawn catches of the same month or a month before.
McArthur's fire‐danger meters expressed as equations
Authors: NOBLE I. R. , GILL A. M. , BARY G. A. V. 
Published: July 2006

AbstractMcArthur's fire‐danger meters for grasslands (Mark 3) and forests (Mark 5) have been widely used in Australia for fire‐danger forecasting and as a guide to fire behaviour. We present a set of equations to describe the data provided on these meters plus equations pertinent to the recently‐produced Mark 5 grassland meter. The equations provide a simple method of describing the forecasting system and are particularly useful for machine processing, and modeling.