bluuebunny/crossref_metadata_2025 huggingface dataset:
Aspects of the selective phytotoxicity of methazole. I. Measurements of species response, spray retention and leaf surface characteristics
Authors: VERITY JULIE , WALKER ALLAN , DRENNAN DONALD S. H.
Published: July 2006

The responses of onion (Allium cepa). Veronica persica, Matricaria matricarioides and Stellaria media to post‐emergence applications of methazole were measured in field and glasshouse experiments. Stellaria media was the most susceptible species and V. persica the least. Plants of all species became more tolerant the larger they were at the time of treatment, and this was most pronounced in onion. Onion generally retained less spray per unit of dry weight than the other three species and retention was less on old compared with young plants, whereas with the weed species, this did not change appreciably with age. There was a progressive increase in the amount of structured crystalline wax on successive onion leaves which resulted in larger contact angles between droplets and the leaf surfaces and lower spray retention per unit of dry weight. There was less wax development on the leaf surfaces, increased spray retention, and increased susceptibility to methazole in onion treated pre‐emergence with ethofumesate thus confirming that these factors are interrelated. While the increased tolerance of onion to methazole with age could be explained in part by decreased retention of herbicide, this was not so for the weed species, and other factors must determine their change in tolerance with age.
Chemical weed control in rainfed cowpea (Vigna unguiculata (L.) Walp) in the Guinea savanna zone of Nigeria
Authors: LAGOKE S. T. O. , CHOUDHARYAND A. H. , CHANDRA‐SINGH D. J.
Published: July 2006

In a field trial in 1978 at Mokwa, southern Guinea savanna zone of Nigeria, metolachlor at 1.5 and 3.0, prometryne at 2.0 and norflurazon and diuron at 1.6 kg/ha combined good weed control with high grain yield of cowpeas. The grain yields with these herbicides were comparable to those of the hoe‐weeded and significantly higher than the weedy controls. In 1979, under wetter conditions, crop injury was observed with prometryne and linuron at 2.0 kg/ha. However, the grain yields obtained with alachlor, metolachlor, chloramben, pendimethalin and norflurazon and their mixtures with prometryne, linuron, diuron or metobromuron were comparable to that of the hoe‐weeded treatment. In 1979 at Samaru, northern Guinea savanna, pendimethalin at 1.5, metolachlor at 3.0 and chlorbromuron and linuron at 1.0 kg/ha gave selective weed control. Prometryne at 2.0 kg/ha was the only herbicide that gave a significantly lower broad‐leaved weed weight than the weedy check but it reduced the crop stand. At 1.0 kg/ha it was tolerated by the crop but failed to control grasses. Metolachlor at 1.5 kg/ha had a significantly higher broad‐leaved weed weight than the weedy check. All theherbicides, except pendimethalin at 3.0 kg/ha, controlled the annual sedges at Samaru.
Studies on the chemical control of blackgrass (Alopecurus myosuroides Huds.) in winter wheat in the West Midlands
Authors: SCOUREY L. R. K. , YOUNG I. , PAGE J. B.
Published: July 2006

In trials carried out in 1978–80, blackgrass populations in winter wheat growing on heavy soil were substantially reduced by all chemical treatments tested, the least effective being methabenzthiazuron. Wild oat populations were also reduced by all treatments except chlofop‐isobutyl and methabenzthiazuron. On average of the 3 years only metoxuron treatment gave wheat yields significantly higher than the unsprayed crop.
Comparative studies of safeners for the prevention of EPTC injury in maize
Authors: GöRöG K. , MUSCHINEK GY. , MUSTÁRDY L. A. , FALUDI‐DÁNIEL Á.
Published: July 2006

The herbicide safener N‐dichloroacetyl‐1‐oxa‐4‐aza‐spiro‐4,5‐decane (AD‐67) is of similar efficiency as the extensively used N.N‐diallyl‐2,2‐dichloroacetamide (R‐25788) and the structurally related 3‐(dichloroacetyl)‐2,2‐dimethyl‐1,3‐oxa‐zolidine (AD‐2) in reducing EPTC [S‐ethyl‐N,N‐dipropyl (thiocarhamate)] injury to maize (Zea mays L. cv. KSC 360). EPTC treatment produces growth retardation and deformities and inhibits CO2 fixation. It does not reduce epicuticular lipids appreciably but affects wax arrangement on the leaf surface. When EPTC is applied together with one of these safeners, these injuries are not observed. All three safeners act similarly. Each prevents the herbicide‐induced aggregation of epicuticular wax of maize, thereby protecting the plants against the formation of areas where the underlying cuticle layers are exposed and increase in transpiration.
Seed production by an arable weed community
Authors: LEGUIZAMÓN E. S. , ROBERTS H. A.
Published: July 2006

After cultivation in early April of a sandy loam soil with 9500 apparently viable seeds/m2 in 0–10 cm, 295 seedlings/m2 emerged of which about half survived to maturity in July. Seeds were dispersed from mid‐June to November and 136,460/m2 were returned to the soil, representing a 14‐fold increase in the seed bank. Application of soil‐acting herbicides reduced the numbers of weeds and the total seed output, but that of tolerant species was increased. Maximum numbers of seeds were 59,980/m2 for Chenopodium album, 39,430/m2 for Sleltaria media and 37,580/m2 for Veronica persica.
The effects of soil texture and moisture on reproductive strategies of Spergula arvensis L. and Plantago major L.
Authors: TRIVEDI SUDHIR , TRIPATHI R. S.
Published: July 2006

The reproductive strategies of two weeds, Spergula arvensis L. and Plantago major L., were studied in relation to soil texture and moisture regime. On sandy soil, daily watering gave greatest dry wt per plant in S. arivensis, while fortnightly watering gave the greatest in P. major. In P. major, seed production was increased with increased moisture stress in sandy soil, but not in garden soil when watered fortnightly. Conversely, S. arvensis showed a decrease in seed number with increasing moisture stress in both soil types. The reproductive effort of S. arvensis was much greater (26.2–63.1%) than P. major (2.3–9.2%). There was greater emphasis on reproduction by S. arvensis under both soil types and various moisture regimes while P. major was characterized by higher allocation to vegetative structures which may confer a competitive advantage by increasing its efficiency of resource capture. Thus, S. arvensis seems to be r‐selected and P. major K‐selected. The differences in the reproductive strategies of the two weeds are discussed with reference to the environmental conditions under which they grow in nature.
A study on seed population dynamics of three weedy species of Eupatorium
Authors: YADAV A.S. , TRIPATHI R.S.
Published: July 2006

The data on seed population dynamics of three weedy species of Eupatorium, viz. E. adenophwrum Spreng., E. riparium Regel and E. odoratum L. have been presented and discussed in the paper. The seed production and seed populations in soil seed bank were estimated, and the fate of buried seeds in soil was followed over a 2‐year period. All the three species of Eupatorium produced a large number of seeds. The seed production of E. riparium per unit area was higher than that of the other two species because of its high population density. In all the three species most of the seeds were found to be present in the top 2 cm of the soil. The viable seed population of the three species of Eupatorium declined exponentially alter their burial in soil showing almost similar mortality patterns. A large proportion of seeds of all the Eupatorium spp. remained under enforced dormancy during their burial in soil with only a small fraction exhibiting induced dormancy. The longevity of the buried seeds increased on account of the dormancy imposed on them. The loss of seeds through degeneration and/or decomposition was rather low.
Population dynamics of Eupatorium adenophorum Spreng. during secondary succession after slash and burn agriculture (jhum) in north eastern India
Authors: KAMAKRISHNAN P.S. , MISHRA B. K.
Published: July 2006

Eupatorium adenophorum Spreng. is an important weedy colonizer in early successional communities developing after slash and burn agriculture (jhum) at higher elevations of the north‐eastern hill regions of India. The relative performance of this species in terms of fecundity and survivorship in successional plant communities has been worked out. A net population increase occurred through both vegetative and sexual reproduction in early successional fallows up to 6 years old, the increase being greatest in a 6‐year fallow. Mortality of seedlings was high in 1‐ and 3‐year fallows, low in a 6‐year fallow but reached 100% in older fallows. Seedling mortality was maximal during the monsoon although some seedlings also died during winter as a result of drought and frost. Mortality of vegetative sprouts followed a similar pattern to that of seedlings. The reproductive potential was reduced with increasing age of the successional communities and in a 15‐year fallow all individuals were non‐reproductive. Since E. adenophorum is able to succeed only in fallows of less than 6 years, repeated short jhum cycles of 4–5 years have had the effect of arresting succession al the weedy stage.
Growth and chemical composition of soybeans as affected by trifluralin and soil salinity
Authors: MAFTOUN M. , BASSIRI A. , SAMENI A. M. , YASREBI J.
Published: July 2006

The combined effects of 0, 1 and 2 ppm trifluralin and five soil salinity levels (0.35, 2, 4, 6 and 8 mS/cm) on growth and chemical composition of soybeans [Glycine max (L.) Merr.] were studied in a glasshouse experiment. Analyses of variance indicated that the interaction of soil salinity and trifluralin was not significant for root and top dry weights and root nodulation. Root dry weight was not affected by trifluralin, whereas 2 ppm trifluralin significantly reduced top dry yield and root nodulation. Shoot and root yields and root nodulation were reduced with increasing soil salinity.

Trifluralin at 1 ppm significantly decreased P concentration and at 2 ppm substantially increased N concentration. Moreover, there was a general trend of an increase in N concentration and a decrease in P concentration with salinity.

The concentration and uptake of Cl and Na increased with increasing soil salinity. Probably large accumulations of Cl and Na and/or water stress caused by high salinity were responsible for growth reductions in salinized media.
Control of problem weeds of maize on the Transvaal Highveld (South Africa). II. Datura stramonium L.
Authors: MALAN C. , VISSER J.H. , GROBBELAAR N.
Published: July 2006

As was described in a previous publication, the influence of a number og herbicides and herbicide mixtures which are being used for the post‐emergence control of weeds in maize on the Transvaal Highveld, have been tested for their efficiency in the control of problem weeds. Both the percentage mortality and percentage dry mass difference between the test plants and the controls 10 days after application of the respective herbicides were used as bioassay methods.

Datura stramonium L. was very susceptible to most of the herbicidal treatments up to the nine‐leaf stage. The reason why it is considered a problem weed should perhaps be sought in the erratic germination of its seeds over a number of years, thus evading common practices of weed control.
Growth and reproduction of Cyperus esculentus L. and Cyperus rotundus L.
Authors: WILLIAMS ROBERT D.
Published: July 2006

The growth of both species (as characterized by their total dry weight, inflorescence dry weight, root and rhizome dry weight and number of shoots per pot) was similar, but they differed in the manner in which the dry weight was partitioned to reproductive structures. Each species partitioned less than 2% of its dry weight into floral formation. However, yellow nutsedge (Cyperus esculentus L.) partitioned only 28% of its dry weight to tubers, whereas purple nutsedge (C. rotundus L.) partitioned 50% of its dry weight to fewer and larger tubers. The allocation of dry weight to reproductive structures was related to changes in day‐length. Yellow nutsedge tuber formation increased as day‐length decreased from 14.5 to 12.5 h, while floral formation did not begin until the day‐length dropped below 14 h. Purple nutsedge formed inflorescences earlier and production continued throughout the remainder of the study, but tuber formation was curvilinear and accelerated as the day‐length decreased.
Factors affecting weed seed germination and seedling growth in lowland rice in Indonesia
Authors: PONS T. L.
Published: July 2006

Experiments were carried out in Indonesia to see whether weeds of lowland rice fields could be managed by manipulation of the water table and what factors affected germination of their seeds. It was found that seeds of two Scirpus spp. germinated when buried in anaerobic soil but not when on the surface, whereas seeds of two Echinochloa spp. germinated when on the surface of both aerobic and anaerobic soils but when buried germinated only in aerobic soil.

The germination of weed seeds was affected to differing extents by submergence in water at depths down to 20 cm. Germination of Fimbristylis littoralis seeds was greatly reduced and of Ludwigia hyssopifolia was complétély inhibited by submergence. Conversely, germination of Monochoria vaginalis seeds was virtually unaffected. It is suggested that the effect of submergence on germination of some species may be due to their reaction to the amplitude of temperature fluctuation. The germination and emergence of seedlings under water were greatly reduced by a cover of Salvinia molesta. The practical importance of these findings is discussed.
Collaborative studies of dose‐response curves obtained with different bioassay methods for soil‐applied herbicides
Authors: NYFFELER A. , GERBER H.‐R. , HURLE K. , PESTEMER W. , SCHMIDT R. R.
Published: July 2006

In a collaborative study by 12 laboratories the reproducibility of bioassay techniques was analysed by comparison and statistical treatment of the ED50‐values (μg herbicide/g soil). Commonlyused bioassay techniques were investigated; two direct seeding methods, a transplanting method and a shoot extension method. The herbicides studied were two photosynthesis inhibitors, atrazine and metribuzin using Lepidium sativum and Brassica rapa as test plants; two germination inhibitors, tri‐allate and trifluralin using Avena sativa as test plant. The mean ED50‐value of atrazine in the direct seeding method was 0.18 with a variation from 0.12 to 0.29 and 0.12 (0.07–0.68) in the transplanting method. The values of metribuzin were 0.05 (0.02–0.11) and 0.03 (0.01–0.15) respectively. The values for triallate were 1.15 (0.50–2.60) in the direct seeding method and 1.10 (0.54–2.53) in the shoot extension method and for trifluralin 3.11 (0.72–18.31) and 1.33 (0.48–2.94) respectively. The reproducibility was best in the shoot extension method. No outliers (confidence intervals lying entirely outside the confidence interval of the overall mean) in the ED50‐values were observed with atrazine and metribuzin when using the direct seeding method, whereas with the germination inhibitors a high number of results (four with tri‐allate, six with trifluralin) could be considered as outliers. A comparison of the use of fresh weight and dry matter showed good agreement between the ED50‐values they gave, with similar reproducibility.
The role of waxes in the uptake of metolachlor into sorghum in relation to the protectant CGA 43089
Authors: EBERT E.
Published: July 2006

The grass weed herbicide metolachlor (2‐chloro‐N‐[2‐ethyl‐6‐methylphenyl]‐N‐[2‐methoxy‐1‐methylethyl]acetamide) which is especially effective against wild millets, inhibits the formation of epicuticular waxes on sorghum leaves. The metolachlor protectant CGA 43089 [α ‐ (cyanomethoximino) ‐ benzacetonitrile] prevents the depletion of the waxes on the leaves of metolachlor‐treated sorghum plants, as demonstrated by scanning electron microscopy. This alteration of the plant surface polymers also changes their permeability to the herbicide. 14C‐metolachlor uptake into isolated coleoptiles and first leaves of sorghum which had been pretreated with the herbicide was increased. Incubation with added protectant reduced the uptake of 14C‐metolachlor. It is postulated that the modifications caused by metolachlor and its protectant to sorghum surface structures influence the action of the herbicide in two ways:

The selectivity observed against sorghum and millet grasses could occur because of an increased uptake of metolachlor through cuticles which are particularly sensitive to the structural changes caused by the herbicide, since the composition of the plant waxes is very species‐specific.

The loss of cuticular integrity is prevented by the protectant CGA 43089, which greatly reduces penetration of metolachlor.
Trifluralin persistence under two different soil and climatic conditions
Authors: SOLBAKKEN E. , HOLE H. , LODE* O. , PEDERSEN T.A.
Published: July 2006

An investigation of the persistence of trifluralin was conducted as field experiments over a two year period at latitudes 60°N and 70°N respectively, paying special attention to the soil and climatic conditions. These experiments included glasshouse bioassays with Lolium multiflorum. gas‐chromatographic residue analyses and qualitative and quantitative studies on soil bacteria. Special attention was devoted to clay minerals as well as to the soil organic matter. 100 g or 500 g of trifluralin a.i. ha−1 were applied in the spring 1978 with a reapplication on half of the area the following spring (1979).

The phytotoxicity of trifluralin appeared more severe on re‐treated plots compared with single applications even at approximately equal residue levels. Trifluralin did not seem to have any real influence on the total number of soil bacteria. A qualitative change of the bacterial flora was however observed as a relative increase of non‐sporeformers, Gram negatives and Actinomy‐cetes and a relative depression of the Coryneform bacteria/Arthrobacter group.

Even at a recommended dosage, a carry‐over phytotoxicity the following year may occur, especially when the content of organic matter in the soil is low. Care should therefore be taken when using this herbicide on the same field in two successive years. The properties of the soil seemed to exert a greater influence than the climatic factors on the persistence of trifluralin.
Fate of glyphosate in Agropyron repens (L.) Beauv. growing under low temperature conditions
Authors: DEVINE M. D. , BANDEEN J. D.
Published: July 2006

Absorption, translocation and distribution of 14C‐glyphosate were examined in Agropyron repens (L.) Beauv. plants growing under field conditions in the autumn. Glyphosate absorption did not increase beyond 3 days after application, whereas translocation to the rhizomes continued up to 7 days after application. The translocated glyphosate accumulated more in new rhizomes than in older parts of the rhizomes. Ten per cent of the glyphosate translocated out of the treated shoot was recovered in younger shoots 7 days after application. Plants harvested the following spring contained less than 20% of the glyphosate originally applied. Although a growth cabinet experiment indicated that 34% of the glyphosate in the rhizomes of treated plants could be remobi‐lized into new aerial shoots, considerably less was recovered in new, aerial shoots in the spring in the field‐grown plants. Freezing experiments showed that glyphosate translocation to the rhizomes was only prevented when cold treatment caused visible damage to A. repens foliage.
Action of chlorfenprop‐methyl on membrane integrity in plant mitochondria
Authors: GAUVRIT C.
Published: July 2006

The action of chlorfenprop‐methyl, chlorfenprop and its cysteine conjugate was studied on potato tuber mitochondria. Chlorfenprop‐methyl altered membrane structure at 250 μM. leading to a loss of membrane integrity. Chlorfenprop and its cysteine conjugate were without any significant effects. From what is known about the rapid hydrolysis of chlorfenprop‐methyl in plant tissues and from the results presented in this paper, it was deduced that alteration in intra‐cellular membrane integrity is not a mechanism of phytotoxic action for chlorfenprop‐methyl.
Interference between velvetleaf (Abutilon theophrasti Medic.) and soybean (Glycine max (L.) Merr.) I. Growth
Authors: DEKKER J. , MEGGITT† W. F.
Published: July 2006

Three field experiments were conduced to evaluate the effect of Abutilon theophrasti on dry matter, branching and flowering node, and seed production of soybean. Low populations (2.4–4.7 plants m−2) of the weed reduced soybean dry matter, flowering node and seed production. The effect was most pronounced on soybean seed yield, and less on flowering node and dry weight production. These effects were due to the presence of A. theophrasti with soybean, and not to changes in plant population. The effect on soybean branching node production was inconsistent between years.
Evolution de l'aptitude à germer des graines d'Amaranthus retroflexus L. récoltées dans différentes conditions, au cours de leur conservation
Authors: CHADOEUF‐HANNEL RÉGINE , INRA G. BARRALIS
Published: July 2006

Dans cette expérimentation est étudié l'effet de la conservation au sec à 20 ± 1°C pendant 6 mois ou dans le sol à 15 cm de la surface pendant un hiver, sur le comportement germinatif des graines d'Amaranthus retroftexus L. récoltées au niveau de l'inflorescence principale sur des plantes portegraines cultivées dans les conditions naturelles ou dans différentes conditions contrôlées de photopériode ou de température. A la récolte, les graines prélevées sur des plantes qui se sout développées tard (juillet) dans les conditions naturelles sont moins dormantes que celles prélevées sur des plantes apparues plus tôt (avril); en conditions eontrôlées, les plantes cultivées à 20°C en jours longs de 16 h donnent des graines plus dormantes que celles récoltées sur des plantes cultivées soit à 20°C en jours courts de 8 h, soit à 25°C en jours longs de 16 h. Après conservation au sec ou dans le sol, cette hétérogénéïté de l'aptitude à germer s'atténue mais n'est jamais totalement supprimée: les graines conservent les caractéristiques acquises lors de leur formation et de leur maturation. A la récolte, pour une condition de culture définie, la dormance des graines produites dépend de l'état physiologique des plantes porte‐graines; après conservation, les graines qui étaient les plus dormantes à la récolte germent mieux que les graines les moins dormantes. Enfin, l'enfouissement a un effet plus favorable sur la levée de dormance des graines que la conservation au sec.
Influence of glyphosate on uptake and translocation of calcium ion in soybean seedlings
Authors: DUKE S. O. , WAUCHOPE R. D. , HOAGLAND R. E. , WILLS G. D.
Published: July 2006

Calcium ion in hydroponic solution with glyphosate [N‐phosphonomethyl (glycine)] did not significantly influence the efficacy of the herbicide in reducing growth of soybean (Glycine max) seedlings. Data from atomic absorption spectroscopy studies revealed that glyphosate reduced Ca2+ uptake and translocation, whether supplied alone or with other metal ions. Results with radiolabelled 45Ca2+ indicated that glyphosate severely retards translocation of Ca2+ from the roots to the leaves and cotyledons but the effect is not detectable until 24 h after exposure to glyphosate.

Influence du glyphosate sur l'absorption el le mourement de I'ion calcium dans des plantules de soja.

L'ion calcium présent dans une solution hydroponique contenant du glyphosate (N‐phosphono‐methyl (glycine) ne modifie pas dc facon significative I'efficacité de I'herbicide dans son action sur la réduction de croissance de plantules de soya. Des données fournies par la spectroscopie d'absorption atomique montrent que le glyphosate reduit l'absorption et le mouvement des ions Ca2+ seuls ou en présence d'ionsd'autresmétaux. Les résultats obtenus avec des ions marqués 45Ca2+ révèlent que le glyphosate retarde notablement le mouvement des ions Ca2+ entre les racines et les feuilles ou les cotylédons mais cet effct n'est pas détectable avant une péríode de 24h suivant l'exposition au glyphosate.
Biological activity of dinitramine in soils
Authors: OKAFOR L.I. , SAGAR G.R. , SHORROCKS V.M.
Published: July 2006

In pot studies with dinitramine the susceptibility of French bean (Pltaseolus vulgaris L.) seedlings to the herbicide was influenced by the depth of sowing the seed and the dose and depth of incorporation of the herbicide.

Maximum phytotoxicity occurred when the seeds of French bean were sown into a zone in which dinitramine had been incorporated. Where the seeds were separated from the herbicidetreated zone by a layer of untreated soil, the susceptibility of the French bean seedlings increased with increasing depth of sowing. The greater the distance between the point of contact with the herbicide and the soil surface the greater was the injury.

Dinitramine is active in the vapour phase, and volatilization and bioactivity were directly related to concentration and inversely related to depth of incorporation and of placement in the soil.
Einfluss von Pflanzenschutzmitteln einer Zuckerrüben‐Spritzfolge auf biologische Aktivitäben und auf den Abbau von Chloridazon im Boden. I. Freilandversuche
Authors: PESTEMER W. , MALKOMES H.‐P.
Published: July 2006

In mehrjährigen Feldversuchen wurde der Einfluss von Chloridazon (Pyramin) — allein und in Kombination mit anderen Pflanzenschutzmitteln einer Zuckerrüben‐Spritzfolge — an drei Standorten mit ähnlichen Boden‐ und Klimabedingungen auf verschiedene bodenbiologisch Aktivitäten (Dehydrogenaseaktivität, Strohabbau) sowie die Abbaubarkeit und Pflanzenverfügbarkeit von Chloridazon im Boden untersucht.

Nach einer anfänglichen lag‐Phase verlief der Abbau von Chloridazon sehr schnell und zeigte in den untersuchten Jahern eine 50%ige Abnahme der Ausgangskonzentration in 18 bis 53 Tagen. Die prozentuale Pflanzenverfügbarketi des Wirkstoffs im Verchältnis zum Gesamtrückstand ging innerhalb von 36 Tagen nach der Applikation von etwa 30% auf etwa 2% zurück. Durch die Präparate der Spritzfolg wurde keine Änderung der Peristenz des Wirkstoffs im Boden herbeigefübrt.

Während die Dehydrogenaseaktivität durch Pyramin allein kaum gehemmt wurde, trat in der Spritzfolge von allem in der obsten Bodenschicht (0–5 cm) in eingen Fällen bis zur Erntezeit eine Hemmung gegenüber der Kontrolle und besonders gegenüber der Behandlung mit Pyramin allein auf. Der Strohabbau wurde nicht beeinflust.

Weder zwischen den Gesamtrückständen an Chloridazon noch deren wasserextrahierbarem Anteil bestanden Korrelationen zu den untersuchten bodenbiologischen Aktivitäten.
Seasonal variation in the emergence of annual weeds — an introductory investigation in Sweden
Authors: HÅKANSSON SIGURD
Published: July 2006

Seeds of thirteen annual weed species were collected in early autumn. Within a few weeks they were incorporated in soil. They were stored either in the field or in climate chambers where seasonal variations in field soil temperature were simulated. Seedling emergence under various conditions was determined at different times, within a period of 1 or 2 years after the incorporation of seeds in soil. Some material was transferred from the storage places at different times of year and placed in cabinets with standardized temperature regimes for 3‐week emergence tests. These showed increased emergence during late autumn and winter and a maximum at some time in winter in both summer and winter annuals. Some winter annuals showed a second maximum in late summer. Counts of seedlings in the storage places, in unstirred soil, showed maximum emergence in spring for both winter and summer annuals — or in summer for Spergula arvensis and, possibly, Capsella bursa‐pastoris. In certain treatments in the field, the soil was stirred once, on different dates, simulating tillage at different limes of year. The emergence following stirring of the soil was greatest in spring for the summer annuals, except for Spergula arvensis, which showed more emergence from early to mid summer. Several winter annuals showed an emergence peak after stirring in late summer or early autumn.

Variations saisonnières dans la levèe des mauvaises herbes annuelles‐étude préliminaire en Suède
Timing of seedling emergence and reproduction in some tropical dicotyledonous weeds
Authors: MARKS M.K.
Published: July 2006

The periodicities of seedling emergence of seventeen dicotyledonous weeds were determined and fourteen of these examined in detail. In addition, the periodicity of vegetative growth and reproductive development was recorded for all dicotyledonous species in the study area.

Field emergence at monthly intervals during one year was compared with the emergence of seedlings from soil transferred to a shade house and kept moist. This comparison suggested that lack of water during the dry season was the dominant factor controlling germination, although several species failed to germinate when given adequate water under shade‐house conditions indicating that innate or induced dormancy also occurred.

Species were separated into two groups based on the liming and duration of their main phenological stages. The first group contained species which had individuals present throughout the year while plants in the second group died during the dry season and reappeared at the start of the wet season. Most species in the former had some individuals flowering or shedding seed all year round while the latter had a short period of vegetative growth followed by prolonged reproduction.

The possibility of using emergence and phenological data for improving tropical weed control is discussed.
A decade of weed research in the Indo‐Canadian Dryland Project
Authors: FRIESEN G. H. , KORWAR G. R.
Published: July 2006

Weed research within the All India Co‐ordinated Research Project for Dryland Agriculture over the past decade has included weed surveys to determine the dominant weed flora in various regions and cropping systems of the country: weed interference studies to determine the losses caused by weeds in various crops, weed control studies involving traditional and improved tillage methods: chemical control of weeds with emphasis on herbicides available in India, and studies of integrated weed‐management systems. Much useful information has been accumulated and improved weed‐control practices have been developed. The strategies for weed‐control research and technology transfer discussed in this paper may be helpful in developing or introducing improved weed control practices in other Third‐World countries.
Etude du stock en semences d'Echinochloa crus‐galli (L.) Beauv. dans le sol des rizières du Gharb (Maroc)
Authors: BOUHACHE M. , BOULET C. , HAMMOUMI M.
Published: July 2006

Des estimations du nombre de caryopses viables d'E. crus‐galli., ont été effectuées è partir d'échan tillons de sol prélevés dans vingt‐six rizières du Gharb (MAROC). Ces dernières ont été choisies selon trois facteurs de stratification: type de sol, rotation et âge de la rizière. La valeur moyenne du stock de caryopses d'E. crus‐galli est de 1285 caryopses au m2 sur 60 cm de profondeur. Sa contribution moyenne au stock total est de 7.2%. Le plan d'échantillonnage a permis d'analyser l'effet sol pour la rotation — 3 années de riz et 3 annés de culture asséchante et l'effet de la rotation sur sol merja (ce type de sol se caractérise par les stocks les plus faibles en rotation — 3 années de riz et 3 annés de culture asséchante; et en rotation — 3 annés de riz et I année de culture asséchante).

Le profil moyen de répartition des caryopses d'E. crus‐galli dans le sol est le suivant: 85%, 12.5% et 2.5% respectivement dans les horizons 0–20, 20–40 et 40–60 cm. Les levées au champ d'E, crus‐galli., de la récolte au semis de la culture suivante, ont représenté 0.65% du stock dans le sol.
Herbaceous vegetation development and weed potential in slash and burn agriculture (Jhum) in N. E. India
Authors: SAXENA K. G. , RAMAKRISHNAN P. S.
Published: July 2006

The patterns of herbaceous vegetation development and weed potential following slash and burn clearing after different lengths of time between the cultivation cycles are described. The early stages of secondary succession following burning tended to conform closely to the ‘initial floristic compositione’ model under shorter cycles of 4 and 6 years between cultivation, but the ‘relay floristicse’ model was found to be more applicable to the cycles of 10 and 20 yearse’ duration. Weed population, in terms of density, biomass and germinable seeds present in the soil, was significantly higher after cycles of 4 and 6 years compared to 10‐ and 20‐year cycles. In all the cycles, however, weed population declined sharply after a year of cropping with an effective weeding programme following the burn.
Sources of viable seed loss in buried dormant and non‐dormant populations of wild oat (Avena fatua L.) seed in Colorado
Authors: ZORNER P. S. , ZIMDAHL R. L. , SCHWEIZER E. E.
Published: July 2006

Buried populations of dormant and non‐dormant wild oat (Avena fatua) seed persisted less than 2 years, depth of burial having very little influence on their survival. The mode of seed disappearence, however, was closely related to their depth in the soil. Seed exhaustion through germination in situ increased with increasing depth in the soil, whereas exhaustion through non‐viability increased with decreasing depth. Physical and induced dormancies are apparently not capable of supporting prolonged persistence of A. fatua seeds in soil. The lack of prolonged persistence of A. fatua seeds in Colorado derives from a lack of genetically programmed embryonic dormancy in these populations and makes A. fatua easier to control in Colorado than in other cereal‐growing regions south of the 43rd parallel because it dramatically reduces the survival of seeds in the soil. The most effective non‐chemical control of this grass weed is achieved by means of the shallowest cultivations possible, carried out as late as possible.
Influence of environmental factors on the activity of ioxynil salt and ester applied to Stellaria media
Authors: MERRITT COLIN R.
Published: July 2006

Experiments were conducted in a glasshouse and controlled‐environment rooms to investigate the effects of temperature, light, soil moisture and humidity on the activity of ioxynil salt and ester formulations applied to Stellaria media L. Raising the temperature after spraying increased the activity of the ester, whilst changes in humidity had little effect. Activity of the salt was increased by high humidity after spraying, whereas low soil moisture before spraying markedly reduced the susceptibility of S. media to both formulations. When the intensity of natural daylight was varied by shading, the activity of ioxynil ester was greatest where post‐spraying light levels were either very low or very high.

Ioxynil activity was consistently greater in the glasshouse than in controlled‐environment rooms. This may be partly due to the wide diurnal fluctuations of temperature and humidity and the occurrence of periods of high light intensity in the glasshouse.
Time of onset of competition and effects of various fractions of an Avena fatua L. population on spring barley
Authors: PETERS N.C.B.
Published: July 2006

The growth and competition of wild oats (Avena fatua L.) emerging at different times, and the time of onset of competition by them were studied using natural populations in spring barley. In one experiment in 1972, wild oats emerging in the 0–0⋅5, 0⋅5–2⋅5, 2⋅5–4 crop leaf stages at densities of 54, 46, 15 m −2 respectively were allowed to compete all season with the crcp. These gave rise to 82, 17 and l% of all seed shed and caused 16%, and two non‐significant yield losses respectively. In two other experiments in 1973, nearly all the wild oats that caused yield losses had emerged by the crop 2˙45 leaf stage. Where wild oats emerging up to the crop 2⋅5 leaf stage were removed, the later ones did not compensate by making extra growth. In one of these experiments in which densities of crop and weed were 416 and 414 m 2, and in the other where they were 295 and 294 m 2 respectively, grain yield losses were significant if the wild oats remained in the crop until the crop had 2⋅5–4⋅5 leaves and 4⋅5–6⋅5 leaves respectively. In a third experiment in 1973 with initial densities of 464 wild oats and 336 barley plants m −2, and where a top dressing of nitrogen was given at the crop 3–4 leaf stage, unlike the other two experiments in 1973 where all nitrogen was applied at sowing, no yield losses resulted unless the wild oats remained in the crop until after the crop 6 leaf stage.
Residualwirkung von Chlortriazin‐Herbiziden im Boden an drei rumänischen Standorten. I. Prognose der Persistenz von Simazin und Atrazin im Boden
Authors: PESTEMER W. , RADULESCU VALERIA , WALKER A. , GHINEA L.
Published: July 2006

An drei Versuchsstationen in Rumänien, die unterschiedliche Klima‐ und Bodeneigenschaften aufweisen, wurde die Verlustrate von Atrazin und Simazin, die mit jeweils 1 und 3 kg AS ha−1 in Parzellen mit und ohne Mais (Zea mays L.) appliziert wurden, in der oberen 10‐cm‐Schicht analysiert. Unabhängig von Dosierung und Pflanzenbewuchs konnte eine weitgehend vergleichbare 50%ige Konzentrationsabnahme am jeweiligen Standort festgestellt werden, die bei Atrazin zwischen 36 und 68 Tagen und bei Simazin zwischen 48 und 70 Tagen lag.

Mit Bodenproben der verschiedenen Standorte wurden weiterhin mit Atrazin Laborversuche durchgeführt, um das Abbauverhalten unter standardisierten Bedingungen und durch Sorptions‐ und Einwaschungsuntersuchungen das Verhalten von Atrazin in diesen Böden zu charakterisieren.

Mit Hilfe von Klimadaten für die entsprechende Periode der Freilandversuche und den entsprechenden Konstanten aus den Laborversuchen bzw. aus Literaturdaten wurde mit einem Computerprogramm die Herbizidpersistenz für Feldbedingungen simuliert. Mit dem Modell konnten im Vergleich zu den gemessenen Werten in fast allen Fällen recht gute Übereinstimmungen festgestellt werden, wobei in einigen Fällen das Modell die Tendenz einer geringfügigen Unterschätzung der tatsächlichen Wirkstoffverluste zeigt. Bei der Anwendung des Simulationsmodells ist eine Vorhersage der Persistenz von Atrazin und Simazin auch unter den extremeren Bedingungen der rumänischen Standorte mit ausreichender Genauigkeit für praktische Belange möglich, ohne aufwendige Analysen durchzuführen.
Regeneration of yarrow (Achillea millefolium L.) rhizome fragments of different length from various depths in the soil
Authors: BOURDÔT G. W.
Published: July 2006

The regenerative response of the rhizomes of Achillea millefolium L. to fragmentation and burial was studied in field experiments on three different soils. The percentage of buds producing shoots (estimated from surviving rhizome fragments) from 4 cm (1·6 nodes), 8 cm (3·8 nodes) and 16 cm (6·7 nodes) rhizome fragments was 63, 44 and 32 respectively averaged over all soils and depths of 5, 10 and 15 cm. The depth at which 50% of the fragments failed to produce an emerged shoot (LD50 depth) was 9·3, 12·4 and 17·9 cm for 4‐, 8‐ and 16‐cm fragments respectively averaged over all soils. No fragments survived on the soil surface. The time of emergence of the first shoots was delayed and the rate of emergence and ultimate shoot population reduced with increasing depth of burial. Dry‐matter production by aerial shoots and new rhizomes decreased linearly with depth of burial of the rhizome fragments. Soil type had no effect on the regeneration of the fragments. The significance of the results for the control of A. millefolium is discussed.
Buried seeds in arable soils in Scotland
Authors: WARWICK MONICA A.
Published: July 2006

Soil from arable areas in Scotland was examined macroscopically for seeds. In terms of the percentage of sites at which they were recorded, Chenopodium album L. (33%), Poa annua L. (22%), Polygonum aviculare L. (41%), Polygonum persicaria L. (39%), Spergula arvensis L. (42%) and Stellaria media (L.) Vill. (44%) were the most common species found. They accounted for 78% of the seeds recovered. There were eighty different species found over the 5 years of the survey. Estimated total weed populations (m−2) ranged from nil to 170000 with an average of 16000 m−2 in the top 20 cm of soil.
Competitive effects of Avena fatua L. plants derived from seeds of different weights
Authors: PETERS N.C.B.
Published: July 2006

A study was made of the caryopsis weights of Avena fatua grown in the field and in pots and of the competitive ability of A. fatua from heavy seed (≥18 mg) and light reed (≤11 mg) grown at a depth of either 25 or 75 mm with spring barley sown at 25 mm.

The weight of field‐ and pot‐grown caryopses of A. fatua types fA, fB and fC ranged from 3 to 25, 5 to 23, and 5 to 25 mg respectively. With one exception, both the field‐ and pot‐grown samples showed a double normal distribution pattern. The mean weights of pot‐grown primary and secondary caryopses of fA, fB and fC were 15 and 9, 19 and 11, and 18 and 11 mg respectively.

In a competition experiment, A. fatua grown from heavy seeds sown at 75 mm depth with an equal number of barley produced 47% more panicles, 54% more seed and 56% more dry weight per plant than plants from light seeds. When barley and both seed weights of A. fatua were sown at 25 mm depth these differences were smaller, being 21, 28 and 34% respectively.

When the barley was at Zadoks stage 87, and when the barley and A. fatua were grown at equal densities at 25 mm depth, the dry weight of barley was reduced from 10·4 to 7·7, and to 5·8 g per plant by light‐ and heavy‐seeded A. fatua, respectively. When the barley was grown at 25 mm and the A. fatua at 75 mm, the weight per barley plant was reduced to 9·5 and 7·2 g by A. fatua plants grown from light and heavy seeds respectively. Reductions in numbers of grain were caused mainly by a reduction in the number of fertile heads.
Basis for changes in glyphosate phytotoxicity to barley by the non‐ionic surfactants Tween 20 and Renex 36*
Authors: O'DONOVAN J. T. , O'SULLIVAN P. A. , CALDWELL C. D.
Published: July 2006

The non‐ionic surfactants, Tween 20 (polyoxy‐ethylene 20 sorbitan monolaurate) and Renex 36 (polyoxyethylene 6‐tridecyl ether) enhanced the retention of a glyphosate‐dye spray solution by barley (Hordeum vulgare L.) leaves. Tween 20 also enhanced absorption of 14C‐glyphosate applied as droplets to barley leaves whereas Renex 36 similarly applied, reduced both absorption and movement of 14C‐glyphosate. Renex 36 alone or mixed with glyphosate increased leakage of electrolytes from barley leaf segments whereas neither Tween 20 nor glyphosate, alone or mixed together, had any effect. No 14C‐glyphosate complexes were detected in mixtures with either surfactant and neither surfactant affected the pH of the glyphosate solution. The results indicate that the reported enhancement of glyphosate phytotoxicity by Tween 20 is due to increased retention and absorption of the herbicide while the reported antagonism caused by Renex 36 is due to reduced glyphosate absorption and movement possibly as a result of alteration of membrane integrity.
Environmental and physiological factors affecting the fate of seeds of yarrow (Achillea millefolium L.) in arable land in New Zealand
Authors: KANNANGARA H. W. , FIELD ROGER J.
Published: July 2006

Yarrow (Achillea millefolium L.) has arisen as a problem weed in arable land in New Zealand. A spring‐sown yarrow population of 58 plants m−2 produced approximately 243000 seeds. These were capable of immediate germination in the autumn, but virtually no germination occurred in the winter and up to 80–100% at other times of the year. Seeds are positively photoblastic, but a considerable percentage of seed (>30%) may germinate in the dark after chilling, coat pricking, exposure to high nitrate concentrations or to alternating temperatures. Seed buried at 32 cm in undisturbed soil lost viability slowly over 4 years while seed in the top 8 cm lost viability almost completely within 2 years.
A new design for a seed germinator with 100 independently temperature controlled cells
Authors: MCLAUGHLIN N. B. , BOWES G. R. , THOMAS A. G. , DYCK F. B. , LINDSAY T. M. , WISE R. F.
Published: July 2006

Design and performance of a 100‐cell seed germinator capable of simultaneously generating 100 different diurnal temperature cycles with extremes lying between 0 and 45°C is discussed. Each individual cell is equipped with a separate electronic temperature controller employing a thermistor for temperature sensing. The set temperature for each cell is determined by a precision reference resistor in the controller circuit. Six different reference resistors corresponding to six different temperatures are provided for each cell. The reference resistors are mounted on plug‐in modules with one module for each cell. Heating or cooling of the individual cells is provided by thermoelectric heat pumps. Temperature cycling, which approximates a sine function, is achieved by switching the six reference resistors, one at a time, into the controller circuits at appropriate times during a 24h period. Each cell is designed to accept a standard 100 mm Petri dish to contain the seeds. The cells have glass covers to allow entry of light essential for germination of some species.

The benefit of using this type of germinator to assess the germination response of Alyssum alyssoides L., Artemisia absinthium L., Euphorbia esula L. and Setaria viridis (L.) Beauv., is discussed. Three dimensional germination response surfaces are given for the four species.
Final distribution is related to rate of spread in alien weeds
Authors: FORCELLA F.
Published: July 2006

Currently important alien weeds that have reached their final distributions are characterized by the high initial rates of spread with which they attained these distributions. Alien weeds, now seemingly unimportant but spreading at high rates, might be tomorrow's noxious weeds. It is suggested that rates of spread of species in a regional alien weed flora that have not yet reached final distributions may be used as indices for identifying future troublesome species. A literature search of several plant ecological attributes revealed that rapid seed germination, especially at low temperatures, may be associated with rapidly spreading weeds.
Biology of Commelina benghalensis L. in south‐eastern Queensland. 1. Growth, development and seed production
Authors: WALKER S. R. , EVENSON J. P.
Published: July 2006

Experiments conducted at Kingaroy in southeastern Queensland, investigated growth, development and seed production of Commelina benghalensis L. a weed of field crops, which produces aerial and underground flowers. Plants were grown from four seed types (large and small seeds from the two types of flowers) in pots exposed to the weather and in the field.

Development was faster, and growth and seed production were greater in the field than in pots. Plants grown from aerial seeds were smaller, developed aerial flowers earlier, and produced more aerial fruits than plants grown from underground seeds. Rhizomes and underground flowers began to develop 6 weeks after emergence on plants from all seed types, prior to the development of aerial flowers. Seed production in the field was 8000 m−2 for plants grown from underground seeds and 12000 m−2 for plants grown from aerial seeds. Small aerial seeds represented 73–79% of the total seed production, large aerial seeds 19–22%, and underground seeds only 1–3%.