bluuebunny/crossref_metadata_2025_split huggingface dataset:
Response of Xanthium strumarium populations to sublethal applications of bentazone
Authors: ZHANG J. , CAVERS P. B. , JASIENIUK M. 
Published: July 2006

Summary: Résumé: ZusammenfassungResponses of 10 natural or agricultural populations of Xanthium strumarium to sublethal rates of bentazone applied post‐emergence were examined under field conditions. Both vegetative growth and reproduction of sprayed plants were affected by the herbicide. Some populations were more tolerant of bentazone than the others, but the degree of herbicide tolerance did not depend on the previous herbicide experience of a population. Bentazone treatment significantly reduced the weight per fruit in some populations, which in turn could affect the survival and growth of the subsequent seedlings. La réponse depopulations de Xanthium strumarium à des doses sublétales de bentazoneNous avons étudié au champ la réponse de dix populations naturelles ou agricoles de Xanthium strumariumà des doses sublétales de bentazone appliquée en post‐levée. L'herbicide affectait la croissance et la reproduction des plantes traitées. Quelques populations étaient plus tolérantes à la bentazone que d'autres, mais le degré de tolérance ne dépendait pas de l'exposition préalable des populations à l'herbicide. La bentazone réduisait significativement le poids des fruits dans quelques populations, ce qui pouvait affecter ensuite la survie et la croissance des jeunes plantes qui en étaient issues. Wirkung subletaler Dosen von Bentazon auf Xanthium strumariumZehn Herkünfte von Xanthium strumarium wurden im Nachauflauf mit subletalen Dosen von Bentazon unter Feldbedingungen behandelt. Sowohl das vegetative Wachstum als auch die Samenbildung der behandelten Pflanzen wurden durch das Herbizid beeinträchtigt. Einige Herkünfte waren weniger empfindlich, doch der Grad der Herbizidempfindlichkeit stand nicht im Einklang mit früheren Erfahrungen über die Wirkung des Herbizids. Durch die Bentazon‐Be‐handlungen nahm das Gewicht der Samen bei einigen Herkünften signifikant ab, so daß ihre Lebensfähigkeit und das Wachstum der Keimpflanzen beeinträchtigt sein könnten.
Implementation of a herbicide simulation model in a geographical information system with an example of a site‐specific application
Authors: LÜCKE A. , GÜNTHER P. , DIEKKRÜGER B. , PESTEMER W. , RICHTER O. 
Published: July 2006

Summary: ZusammenfassungA Geographical Information System (GIS) was combined with a model for simulating leaching and degradation of herbicides. The model uses first–order kinetics to simulate degradation, and a cascade model to simulate transport. This system was tested with data from a 16 km2 research catchment in northern Germany. Geometrical, topological, and soil data of this area were stored in a GIS. For the whole area, divided into small homogeneous sites (ecotopes), model runs were carried out. The system is able to handle data for all ecotopes automatically and to present calculated results on the behaviour of herbicides as distributed over time and depth for the area. An application of ethofumesate made in sugar–beet in spring and recropping of winter wheat after beet harvest was modelled. Degradation/sorption parameters were estimated from similar soils. Simulation results showed slower degradation in the sandy sites of the catchment, compared to the more loamy regions. Residues of herbicide remaining after beet harvest were greater than 20% of the applied dose in the sandy soils after 150 days. Hence, high risk of damage to the following crop of winter wheat was predicted. At the other sites residues remaining were between 2% and 20% of the applied dose. Einbindung eines Simulationsmodells zum Herbizidverhalten in ein Geographisches Informationssystem–Beispiel zur schlagspezifischen AnwendungEin Geographisches Informationssystem (GIS) wurde mit einem Simulationsmodell für Herbizidabbau und –einwaschung kombiniert. Grundlage der Abbausimulation ist eine Kinetik 1. Ordnung, der Transport im Boden wird mit Hilfe eines Kaskadenmodells berechnet. Das System wurde in einem Intensiv–Untersuchungsgebiet (16 km2) in Norddeutschland getestet. Geometrische und topologische Daten der Fläche sowie Bodendaten sind im GIS gespeichert. Für die gesamte Fläche, die in kleine homogene Teilflächen (Ökotope) aufgeteilt wurde, wurden Simulationsberechnungen durchgeführt. Das System ist in der Lage, Daten für alle Ökotope automatisch bereitzustellen und die Ergebnisse zum Einwaschungs– und Abbauverhalten für die gesamte Fläche in ihrer Verteilung über Zeit und Tiefe darzustellen. Als Szenario wurde die Applikation von Ethofumesat in Zuckerrüben im Frühjahr mit einem Nachbau von Winterweizen nach der Rübenemte gewählt. Abbauund Sorptionsparameter waren in ähnlichen Böden ermittelt worden. Die Simulationsergebnisse zeigten einen langsameren Abbau in den sandigen Böden verglichen mit den lehmigen. In den sandigen Böden lagen die Rückstandsgehalte nach 150 Tagen übe 20 % der Ausgangskonzentration, wodurch ein hohes Nachbaurisiko für Winterweizen prognostiziert wurde. Für den Rest der Fläche lagen die Rückstände zwischen 2% und 20% der Ausgangskonzentration.
The effect of nitrogen, plant density and competition between Bromus sterilis and three perennial grasses: the implications for boundary strip management
Authors: REW L.J. , FROUD–WILLIAMS R.J. , BOATMAN N.D. 
Published: July 2006

SummaryThe competitive ability of Festuca rubra L., Hoicus lanatus L. and Poa trivialis L. when grown from seed, in monoculture and in 1:1 additive mixtures with Bromus sterilis L. was studied. B. sterilis was more aggressive when grown in additive mixtures with F. rubra than P. trivialis or H. lanatus. H. lanatus was less dominated by B. sterilis at the second harvest; visual observations suggested that this dichotomy was due to its slower initial growth rate, and its subsequent dense vegetative growth habit. There was no statistically significant difference between the Relative Yield Total (RYT) of B. sterilis in additive mixtures with F. rubra, H. lanatus or P. trivialis, indicating that they were competing for the same resources. B. sterilis produced significantly more reproductive tillers and seeds as a result of nitrogen application, and such production was accentuated in the absence of interspecific competition. The implications of sown grass strips for field margin management are discussed.
Competition between Ridolfia segetum and sunflower
Authors: CARRANZA P. , SAAVEDRA M. , GARCIA–TORRES L. 
Published: July 2006

SummaryStudies on competition between Ridolfia segetum Maris, and sunflower (Helianthemum annuus L.) were conducted at eight locations in southern Spain in 1990 and 1991. in order to define competition models and to estimate from these economic thresholds as affected by crop inputs and potential yields. Competition losses in sunflower crops ranged from 19% to 56% of weed–free yields. There were slightly better correlations between percentage sunflower reduction and weed density than with weed dry weight, (−0.66 and −0.59, respectively). The weed competitive index, or sunflower crop dry weight reduction per unit dry weight of R. segetum, was 1.09. The percentage yield losses due to weed density (NPRt) were fitted to multiple linear, quadratic, exponential and hyperbolic models. The hyperbolic equation, %RSY=100 (1+1/b*NPRt)−1, where b=0.14 and is the R. segetum competitive ability index, had the lowest error sum of squares (SSE), and gave the best biological explanation for the competition response. Early emergence (before mid–March) made weeds about 1.5 times more competitive than late emergence. The economic threshold to offset the cost of a shallow post–emergence tillage, assuming 70% control efficiency, ranged from about 2.5 plants m −2 for low–yielding crops(1200kgha−1) to less than one plant m−2 for higher–yielding crops (2800 kg ha−1).
Foliar absorption and translocation of nicosulfuron and rimsulfuron in five annual weed species
Authors: MEKKI M. , LEROUX G. D. 
Published: July 2006

Summary Ambrosia artemisüfolia L. (common ragweed) and Digitaria ischaemum Schreb. (smooth crabgrass) are not controlled by nicosulfuron and rimsulfuron at the highest recommended application rates, whereas Panicum miliaceum L. (wild proso millet), Amaranthus retroflexus L. (redroot pigweed) and Avena fatua L. (wild oat) are susceptible. The foliar absorption and translocation of 14C‐nicosulfuron and 14C‐rimsulf uron were studied in these weed species up to 48 h after treatment (HAT). Differences in herbicide uptake and translocation were not correlated with the species susceptibility. By 48 HAT, more than 50% of both herbicides remained on the treated leaf surface. Foliar absorption of rimsulfuron was greater than that of nicosulfuron in A. retroflexus, P. miliaceum and A. artemisüfolia. Most of the absorbed herbicide remained in the treated leaf of each weed species. Export of 14C–nicosulfuron ranged from 28 to 54% of that absorbed, in contrast to 15 to 39% for 14C–rimsulfuron. The absorption and translocation rates of both herbicides were highest within the initial 6 HAT, and decreased thereafter. Both herbicides showed approximately the same distribution pattern within each weed species.
Geographical differentiation in allozyme variation in Rumex acetosella subspecies acetosella and angiocarpus
Authors: KORPELAINEN H. 
Published: July 2006

SummaryElectrophoretic examination of the hexaploid Rumex acetosella L. revealed a substantial amount of genetic variation. Both the genotype frequencies and the distribution of genotypes varied greatly between populations. The North American populations of ssp. angiocarpus possessed less genetic variation than did the European populations of ssp. acetosella or angiocarpus, which may be due to the history of the species. The European populations of ssp. acetosella and angiocarpus appeared to be genetically more similar than the angiocarpus populations from different continents. It is likely that these two subspecies do hybridize when their populations are sympatric. The results do not confirm the presence of an association between morphometric and allozyme variation in R. acetosella.
Evaluation of three empirical models depicting Ambrosia artemisiifolia competition in white bean
Authors: CHIKOYE D. , SWANTON C. J. 
Published: July 2006

SummaryThe performance of three empirical models describing white bean yield loss (YL) from common ragweed competition was compared using field experiments from Staffa and Woodstock, both in Ontario, Canada, in 1991 and 1992. One model was based upon both weed density and relative time of emergence. The other two models described yield loss as a function of weed leaf area relative to the crop. The model based on both weed density and relative time of emergence best described the data sets. The predicted maximum yield loss (A) and the parameter for relative time of weed emergence (C) varied across locations and years whereas the yield loss at low weed density (I) was relatively more consistent across locations and years. Use of thermal time (base temperature=10oC) rather than calendar days did not change the overall fit of the model, but reduced the value of the parameter for the relative time of weed emergence (C). The two parameter leaf area model accounting for maximum yield loss (m) gave a better fit to the data compared with the one parameter model. The relative damage coefficient (q) varied with time of leaf area assessment, location and year. Values of q calculated from relative leaf area growth rates of the crop and weed were similar to observed values.The relationship between q and accumulated thermal time was linear but varied with location and year. As management tools, models based upon relative leaf area have advantages over models based on density and relative time of emergence since the level of weed infestation needs only to be assessed once, whereas density and emergence time require frequent observations. The ability to assess accurately and quickly both the crop and weed leaf area, however, may limit the practical application of models based on leaf area. The inability of empirical models to account for year–to–year variation in environmental conditions was observed.
Seasonal emergence of weeds in cultivated soil in New Zealand
Authors: POPAY A. I. , COX T. I. , INGLE A. , KERR R. 
Published: July 2006

SummaryPatterns of seedling emergence of ten weed species from soil cultivated at intervals of approximately one month are described. All species examined showed clearly defined emergence patterns. Polygonum persicaria L. seedlings emerged in spring and early summer. Seedlings of Chenopodium album agg., Portulaca oleracea L. and Solanum nigrum L. emerged in late spring, summer and early autumn.Plantago major L., Rumex spp. (mostly R. obtusifolius L.) and Trifolium spp. (mostly T. repens L.) emerged mostly in spring and early summer. Coronopus didymus (L.) Sm. and Juncus bufonius L. tended to emerge in both autumn and spring.Veronica persica Poir. emerged in spring, summer and autumn. Close similarity between emergence patterns in New Zealand and northern Europe, despite differences in rainfall and temperature, suggests that annual dormancy:nondormancy cycles of seeds buried in the soil are largely responsible for seedling emergence patterns. In New Zealand, seedling emergence tended to be more spread out than in Europe, although seasonal patterns were still distinct. Further work on dormancy cycles in these species would be useful, as would a comparison of the factors inducing and breaking dormancy of comparable seed populations in northern and southern Europe and New Zealand. When seeds were left buried for several years before being encouraged to germinate, seedling emergence patterns tended to be of smaller amplitude, although the overall patterns were still very similar.
Effects of dose and application timing on the seed production of three weed species treated with MCPA or tribenuron‐methyl
Authors: ANDERSSON L. 
Published: July 2006

SummaryThe seed production of Fallopia convolvulus (L.) A. Love, Galium spurium L, and Thlaspi arvense L., treated with MCPA or tribenuron‐methyl, was studied in a pot experiment. The herbicides were applied in doses from 1/16 to 1/l of a full dose at five different growth stages. The largest reduction of seed production was observed on plants treated when one true leaf had developed (F. convolvulus, both herbicides) or at the beginning of the generative phase (G. spurium treated with tribenuron‐methyl and T. arvense treated with either herbicide). Tribenuron‐methyl (0.375 g a.i. ha−1) or MCPA (0.1875 kg a.i. ha−1) applied at bolting stage was enough to reduce the seed production of T. arvense by 83% and 100%, respectively. The seed production of F. convolvulus, treated with 0.75 kg MCPA at the cotyledon stage, was reduced by 70%. Plants of G. spurium with 5–9 axillary shoots, treated with 3 g tribenuron‐methyl, produced 45% fewer seeds than the control. Both herbicides (at least at the highest doses) reduced seed production of all three species more than shoot dry matter.
Influence of herbicide application rate and timings for post‐emergence control of Sorghum halepense (L.) Pers. maize
Authors: ELEFTHEROHORINOS I. G. , KOTOULA‐SYKA E. 
Published: July 2006

SummaryField experiments were carried out in Greece from 1990 to 1992 to study the effect of application timing and rate of nicosulfuron and rimsulfuron on Sorghum halepense (L.) Pers. control and maize yield. All herbicide rates are given in terms of active ingredient (a.i.). Nicosulfuron applied at 22.5, 30.0 and 37.5 g ha−1 to S. halepense at height 20–35 cm provided greater than 93% control 90 days after treatment, while rimsulfuron applied at 7.5,10.0 and 12.5 g ha−1 resulted in 81–91% control. Split applications of nicosulfuron and rimsulfuron, as well as tank‐mixtures of nicosulfuron+rimsulfuron, gave 91–94% control. Maize yield in all herbicide treatments was greater than that of the weed‐infested control and similar to that of the hand‐weeded control. S. halepense control with nicosulfuron and rimsulfuron applied to plants 20–35 cm tall was greater than that obtained with their application to plants 5–15, 10–20 or 35–60 cm tall. Rates of 10 and 20 g ha−1 of rimsulfuron provided control of S. halepense similar to or significantly lower than that achieved with 30 and 60 g ha−1 of nicosulfuron, respectively. Maize yield produced by all herbicide treatments applied at any time was significantly greater than that of the weed‐infested control.
Clonal growth and fragment regeneration of Rumex obtusifolius L.
Authors: PINO J. , HAGGAR R. J. , SANS F. X. , MASALLES R. M. , HAMILTON R. N. SACKVILLE 
Published: July 2006

SummaryClonal growth and fragment regeneration of Rumex obtusifolius L. were analysed in two dif ferent studies. Clonal growth system was des cribed by a morphological study of underground structure of different‐aged individuals, using maximal branching order in the stem system as an age estimator. Glasshouse experiments were conducted, testing the regenerative capacity of different below‐ground parts and the estab lishment of above root‐collar fragments planted at different depths under contrasting water regimes. Results showed the presence of a ‘phalanx’ type clonal growth system in grassland populations of Rumex. The main structure in volved in clonal growth proved to be the stem system; the region above the root collar was also the only part able to regrow after damage. Stem fragment regeneration occurred to depths of 15 cm, but was prevented in soils maintained at waterlogging and field capacity. The significance of these results in relation to nonchemical con trol of Rumex populations in grasslands is discussed.
Biology of Striga hermonthica (Scrophulariaceae) in Sahelian Mali: effects on pearl millet yield and prospects of control
Authors: WEBB M. , SMITH M C. 
Published: July 2006

SummaryAspects of the population: dynamics of Striga hermonthica (Del.) Benth. on pearl millet (Pennisetum americanum (L.) K. Schum.) were studied in Sahelian Mali. Seasonal development was recorded and density‐dependent mortality and fecundity in post‐emergent populations investigated. An attempt was also made to assess yield loss due to S. hermonthica attack using a regression approach. The first S. hermonthica plants emerged 42 days after crop germination, and the minimum time to complete the life cycle from emergence was 56 days. Results indicated a premature mortality of 66% in emerged populations. The growth stage reached by the time of host plant death appeared to be important in determining survival to maturity, premature mortality being greatest in plants that had not reached flowering by this time. The potential seed output per plant was estimated at 10 985. There was no evidence that the fecundity of S. hermonthica was affected by the density of emerged populations. Regression models showed a significant relationship between millet yield and emerged S. hermonthica density. The results suggest that lower densities give a relatively larger decrease in yield per S. hermonthica plant. The results of the study are discussed in relation to their implications for control.
Modelling the effect of duration of weed competition, weed density and weed competitiveness on seeded, irrigated onion
Authors: DUNAN C. M. , WESTRA P. , MOORE F. , CHAPMAN P. 
Published: July 2006

SummaryWeed removal experiments were conducted in growers' fields in northern Colorado to assess the effect of duration of competition, weed density, weed competitiveness and crop density on irrigated seeded onion (Allium cepa L.). Duration of competition, expressed in thermal time units (TTUs) with a base of 7.2^C, explained 65% of the variation in the reduction of onion relative yield. The first significant reduction in onion relative yield was at 90 TTUs, averaged over weed load (weed density adjusted by competitiveness) and onion density. A polynomial multiple regression model, accounting for duration of competition and weed load, explained 75% of the variation in onion relative yield. A non‐linear multiple regression model, combining a gamma function response of relative yield to duration of competition plus a hyperbolic response of relative yield to weed load, was as good a predictor and a better description of the system. Onion relative yield was more sensitive to the duration of weed competition than to weed load. Bulb size class distribution and the resulting average onion price were affected by weed competition. Polynomial models were used to describe changes in bulb size class proportions as a function of duration of competition, weed load and onion density.
A technique for mapping the spatial distribution of Elymus repots, with estimates of the potential reduction in herbicide usage from patch spraying
Authors: REW L. J. , CUSSANS G. W. , MUGGLESTONE M. A. , MILLER P. C. H. 
Published: July 2006

SummaryThe spatial distribution of Elymus repens L. was mapped in five cereal fields during the 1994 season. Weed maps were created using a semi‐automated system mounted on a vehicle that travelled up the tramlines, centred on a 12‐m‐wide spray boom. Two operators detected weeds visually and recorded their presence and density by means of a simple push‐button system that recorded data from (2 × 1) m2 areas, or cells, across the boom section on a portable computer. The position of the vehicle along the tramline was monitored by integrating output from a wheel sensor. Eight tramlines of one field were mapped three times consecutively, to assess detection and navigational error. Pair‐wise comparisons of the three runs gave approximately 85% repeatability on presence/ absence data, 80% on zero/low‐ or high‐density data and 85% on low/high‐density data when weeds were definitely present. Simultaneous comparisons of all three runs gave 78%, 69% and 75% respectively. Repeated runs of tramlines up to 550 m long recorded mean differences of approximately 2 m with a maximum error of 14 m (2.5%). The spatial distribution of E. repens within the five fields was visibly patchy, but the size and morphology of patches varied both within and between fields. Thus, the potential reduction in herbicide usage as a result of patch spraying varied with patch morphology and infestation level. The effect of lowering the resolution from six (2 × 1) m2 cells to three (4 × 1) m2 cells across the 12‐m boom width showed little change in potential reduction in herbicide usage.
Growth and competitiveness of paraquat‐resistant and ‐susceptible biotypes of Hordeum leporinum
Authors: PURBA E. , PRESTON C. , POWLES S. B. 
Published: July 2006

SummaryGrowth, competitiveness and seed characteristics were compared in paraquat‐resistant and ‐susceptible biotypes of Hordeum leporinum Link collected from neighbouring fields. Dry weight and tiller production were greater in the susceptible biotype as compared with the resistant biotype in the absence of competition, however, the reproductive output was the same. Competitiveness in the field was estimated using a replacement series design that showed only slight differences between the two biotypes. There were no differences in seed weight, number of seeds per head, seed viability or seedling establishment between the two biotypes. When grown in pots in monoculture, the production of tillers was the same throughout the growing season, but inflorescences appeared on the resistant biotype earlier and matured earlier than did those of the susceptible biotype. We conclude that under field conditions the resistant biotype does not show a reduction in fitness as compared with the susceptible biotype.