bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative relationships between the weed flora after cultivation and the seed population in the soil
Authors: ROBERTS H.A. , RICKETTS MARGARET E.
Published: July 2006

Eighty comparisons were made between the numbers of weed seedlings emerging after seedbed preparation and the numbers of apparently viable seeds extracted by sieving and flotation from samples of the top 10 cm of soil. When soil moisture was adequate, the total seedling numbers represented 3–6% of the numbers of seeds; when dry weather followed cultivation, the percentages were lower than this. The percentages were relatively high for Poa annua L. and Stellaria media (L.) Vill. but low for Chenopodium album L. and Papaver spp. Relatively high numbers of seeds of Potygonum aviculare L. gave rise to seedlings in early spring but few appeared on seedbeds prepared after mid‐May; the reverse was true for Aphanes arvehsis L. It is suggested that data of this kind could provide a basis for predicting weed floras following cultivation at any time of year from determinations of seed numbers made at the start of the year.
Adsorption and bioactivity of di‐allate, tri‐allate and trifluralin*
Authors: GROVER RAJ , BANTING JAMES D. , MORSE PAMELA M.
Published: July 2006

Studies were conducled to cstmiate the adsorption parameter k and the bioactivity (in terms of G R50) of di‐allate [S‐2,3‐dichloroallyl N, N‐di‐isopropyl (thiocar bamate)], iri‐allate [S‐2,3,3‐trichloroallyl N, N ‐di‐isopropyl (thiocar bamate], and [trifiuralin (2,6‐dinitro N, N‐dlpropyl‐4‐trifluoromelhylaniline) in a number of Saskatchewan soil. The k values ratiged from 5 for di‐allate adsorption m Asquilh loamy sand to 315 for trifluralin adsorption on Melfort loam and were closely related to the soil organic matter content. The relative degree of adsorption was irifluralin > tri‐allate >di‐allaie. For each herbicide, the G R50 values were positively correlated wich organic matter conienl atid wilh k. It was suggested that these nonionic herbicides may be amenable to a predictive approach for field application rates in different soils. Among herbicides for any one soil, however, there was not the same relationship between G R50andk. since the G R50 was least for trifluralin and there was no significant difference between di‐allate and tri‐allate.
The basis of field tolerance of field bean and pea to dimefuron*
Authors: GLASGOW J. L. , DICKS J. W.
Published: July 2006

Ficld bean (Vicia fab a L. cv. Maris Bead) was susceptible both to simazine and dimefuron applied to the root system in culture solution at concentrations of 0–5 and above. Pea (Pisum satirum L. cv. Kelvedon Wonder). however, exhibited significantly greater tolerance them field bean to dimefuron between concentrations of 0.5 and 1.0. The Hill activity of isolated chloroplasts from pea was more sensitive to dimefuron than that from field bean qualitative (autoradiography) and quantitative experiments dcmonstrated that root‐applied 14C dimefuron was more readily transported to the shoot system in bean than in pea. A double‐pot experiment revealed that the effective site of uptake by the field bean is the root system: foliar uptake of 14C‐dimefuron was shown, but little movement of label from the treated leaf oceurred. Adsorption of dimefuron on a calcareous loam soil was relatively low. It is concluded that fieltolerance exhibited by field bean to pre‐emergence applications of dimefuron is due principally to depth protection: in pea. retention in the root provides an additional basis iS for tolerance.
Germination tests on thirty‐two East African weed species
Authors: FENNER M.
Published: July 2006

The seeds of thirty‐two species of common East African weeds were set to germinate in the light and in the dark. Eighteen species with more than 40% germination in the light were also germinated in leaf shade and in neutural shade of equal intensity. Germination of fifteen of these was inhibited by darkness, and of sixteen by leaf shade, with complete inhibition in six species. A high degree of dormancy was found in fourteen species. Only one species in this group responded to alternate wetting and drying of the seeds. In eight species dormancy was less in older seeds.

The ecological implications of the results are briefly discussed, and comparisons made with temperate weeds.
The effects of glyphosate on the development and cell infrastructure of white mustard (Sinapis alba L.) seedlings
Authors: UOTILA M. , EVJEN K. , IVERSEN T.‐H.
Published: July 2006

The phytotoxicity of glyphosate(N‐(phosphonomethyl glycine) to seedlings of white mustard (Sinapis alba) cultivated indoors was studied. Yellowing and wrinkling of leaves was observed, necrotic spots appeared and the elongation of the seedlings was significantly reduced at doses 0–49 kg ai/ha and above. Only when sprayed at 4–97 kg ai/ha was the effect of glyphosate 100% lethal (5–7 days after spraying) At the highest concentration of herbicide a marked decrease in chlorophyll content was found but with 0–49 kg ai/ha the chlorophyll content was found to be higher than that in the leaves of control plants.

Two and fourteen days after spraying with glyphosate and the commercial product samples of leaf and stem were harvested for electron microscopy. Cellular defects in the leaves ranging from slight swelling to complete disruption of the chloroplasts were detected at the two highest herbicide doses 48 h after spraying. These defects were intensified with time und in addition other sub‐morphological changes occurred: decrease in starch grain content, an increase in the number of dictyosomes and mitochondria, disruption of tonoplasts and increase of plastoglobuli In the more central parts of stem segments the commercial product resulted in greater cellular effects than did glyphosate. It is suggested that the differences may be due to the surfactant.
Allelopathic potential of Datura stramonium L. (Thorn‐apple)
Authors: LOVETT J. V. , LEVITT JUDY , DUFFIELD A. M. , SMITH N.G.
Published: July 2006

The effects of different concentrations of aqueous leachate of Datura stramonium seeds and leaves on germination and radicle elongation of Linum usitatissimum were examined.

Germination and radicle elongation of L. usitatissimum were depressed at high leachate concentrations. Radicle elongation usually appeared more sensitive to the effects of the leachate than did germination. Preliminary investigations showed that D. stramonium leaf leachate had similar effects to those of seed leachate.

Chemical analysis of the leachates by spot‐tests and by high‐voltage electrophoresis indicated the presence of tropane alkaloids, in particular scopolamine. The presence of both scopolamine and hyoscyamine was confirmed by gas chromatography/mass spectrometry. It was shown that varying concentrations of pure scopolamine and scopolamine plus hyoscyamine solutions had effects similar to those of seed and leaf leachates on germination and radicle elongation of L. usitatissimum.
Seed banks of soils under vegetable cropping in England
Authors: ROBERTS H. A. , NEILSON JUNE E.
Published: July 2006

Estimates of viable weed seeds in soil samples taken in 1968–1975 from 89 vegetable fields in England gave a median value of 4120 m−2 in 0–15 cm. Poa annua, Stellaria media and Matricaria matricarioides occurred most frequently, and nine species accounted for 72% of all seeds found. The numbers of seeds were lower than those from a survey made a decade earlier but the species occurring most frequently were the same; M. matricarioides, however, appeared to have increased in relative importance.
Loss of herbicides from ground sprayers
Authors: COMBELLACK J. H.
Published: July 2006

The effect of herbicide spray losses on non‐target areas is reviewed. The parameters governing both exo‐ and endo‐losses of herbicides are delineated and the literature on the processes involved is reviewed. The reported studies of droplet drift and vapour drift are assessed. These reviews are then related to the mathematical models developed to describe the spray loss problem. Recommendations are made as to the areas of research needed to improve the predictions of herbicide losses and their effects.
The effect of shade on the growth of variegated thistle (Silybum marianum L.) and cotton thistle (Onopordum sp.)*
Authors: POOK E. W.
Published: July 2006

The effects of shading on growth of the annual, variegated thistle (Silybum marianum L.) and the biennial, cotton thistle (Onopordum sp.*) were studied in an unheated glasshouse during winter. The response to relative level of irradiance (r.l.i.) of both thistles was similar, seedling growth being systematically reduced with increased shading. Relative growth rates of seedlings of both thistles were virtually identical at all levels of irradiance up to 0.68 r.l.i. Light compensation points for growth were close to 0.024 r.l.i., equivalent to c. 2 W m−2 photosynthelically active radiation under the winter conditions. Increased shading progressively delayed time of initiation of leaves and decreased their total number at harvest. Apart from reduction in plant size, increased shading had only minor effects on gross seedling morphology until irradiance was reduced to less than 0.20 r.l.i. Although the thistle seedlings are quite shade tolerant, it is suggested that heavy shading by persistent pasture species in cool seasons could contribute to the control of thistle infestations in subhumid tableland environments of southeastern Australia.
EPTC persistence and phytotoxicity influenced by pH and manure
Authors: LODE O. , SKUTERUD R.
Published: July 2006

The degradation of EPTC and consequently its phytotoxicity to ryegrass (Lolium perenne L.) was greatly influenced by the pH in the three sail types tested. On raising the pH from approximately 5 to 7 the microflora and the degradation in the soil increased and the phytotoxic period was shortened by 2–3 weeks in glasshouse experiments. A similar increase in degradation of EPTC was also found on adding manure.

The results indicated that EPTC could be ineffective in soils with high microbiological activity. On the other hand, a delayed breakdown of EPTC on acid soils could result in damage to the crops. In the period 2–4 weeks alter the disappearance of phytotoxicity there was an increase in the yield of ryegrass. This corresponded to a concentration of 0.1 g/g or less of EPTC in the soil.
Competition between annual weeds and vining peas grown at a range of population densities: effects on the crop
Authors: LAWSON H. M.
Published: July 2006

Competition between annual weeds and vining peas (Pisum sativum L.) at five target population densities between 11 and 194 plants/m2 was examined by means of periodic destructive sampling of weedy and weed‐free plots. A further area of each plot was cut and vined to assess yields. Weeds impaired vegetative development, particularly by reducing tillering in low density crops. This resulted in weedy plots having fewer pods per plant at harvest but a lower proportion of flat pods than weed‐free plots. Weeds had no effect on numbers or weights of peas in full pods nor on tenderometer values of samples of vined peas.

Adverse effects of weeds on the growth of individual crop plants decreased with increasing crop density. However, at lower crop densities many of the additional pods on weed‐free plots contributed little to vined yield, while at higher densities, direct or indirect effects of weeds increased the problem of maintaining sufficient photosynthetic area during pod swelling to prevent pod abscission and poor ovule development. Regression analysis of yield on crop density and of yield on numbers of pods per plant showed that vined yield per hectare was reduced by weeds by a constant amount across the range of densities and numbers of pods examined. Vining throughput was also reduced in weedy as compared with weed‐free crops, even on high density plots where little or no weed vegetation remained at harvest.

In general, weed presence had effects similar to those caused by increasing crop density, but without the additional contribution to yield made by extra plants. Higher density crops suppressed weeds very effectively but were no less vulnerable to yield loss than those of lower density; they therefore merit just as much attention to effective weed control as crops suffering more visibly from competition by weeds.
Response of teff (Eragrostis tef(Zucc.) Trotter) to 2, 4‐D and MCPA at various growth stages
Authors: MERSIE WONDIMAGEGNEHU , PARKER C.
Published: July 2006

Teff (Eragrostis tef (Zucc.) Trotter) cv.DZ‐01‐ 354 was sprayed at one‐, three‐, four‐, five‐ and six‐leaf stages with 2.4‐D (amine salt) and MCPA (potassium salt) each at 0.75 and 1.5 kg a.e. ha−1. Teff was also grown in different temperature regimes to see the relation between apical and vegetative development. Photomicrographs were made to determine the stage of development of the growing point and dry matter measurements were made to assess the effects of the herbieide. Teff sprayed at the one leaf stage was killed by both herbieides. At the three‐ and four‐leaf stages 2, 4‐D at both rates and MCPA at 1.5 kg a.i. ha−1 caused severe leaf deformities and reduced dry weights. Less severe effects were noted at the five‐leaf stage indicating that teff was then more tolerant to these herbicides. This coincided with a fully elongated shoot apex. However, when sprayed at the six‐leaf stage there was evidence of herbicide‐induced panicle deformities. Teff was more susceptible to 2, 4‐D than to MCPA and both affected the roots more than the shoots. A close correlation was found between leaf number and the development of shoot apex under all the different temperature and day length conditions.
Etudes préliminaires sur la concurrence entre Solanum nigrum ssp. eu‐nigrum L. (morelle noire) et Lycopersicon esculentum Mill. (tomate) en culture repiquée
Authors: MAILLET J. , ABDEL‐FATAH H.
Published: July 2006

L'accroissement de production des tomates (Lycopersicon esculentum Mill.) de conserverie en semis direct et l'utilisation d'herbicides sélectifs ont entraîné la prolifération de Solanum nigrum L. dans le Sud‐est de la France. Les estimations réalisées sur le terrain ont montré l'action préjudiciable de faibles populations de morelles; un essai a été mis en place afin de déterminer un seuil de nuisibilité. Dans les conditions d'essai, une droite de régression a pu être tracée en fonction de la densité de morelle/m linéaire et du logarithme du rendement.
The influence of climatic factors on metoxuron activity on Bromus sterilis L.
Authors: BLAIR A.M. , RICHARDSON W.G. , WEST T.M.
Published: July 2006

Metoxuron was more active when Bromus sterilis L. (sterile brome) plants were kept under cool (10/6°C day/night) compared with warm (26/16°C) temperatures after spraying. The effect of warmer temperatures required exposure for more than 3 days. Metoxuron activity was unaflected by a cold exposure (0/‐2°C or 4/2°C) for a 24‐h period shortly before or after spraying.

Greater damage occurred when plants were kept in high relative humidity (r.h.) (95/98% r.h. day/nighl) after spraying than at 75/86% r.h. or at 50/75% r.h. Increasing soil moisture from 11.5 to 21.5 g water 100 g−1 dry soil also resulted in increased metoxuron activity. Metoxuron was less active under severe shading.

There was little evidence in these studies that metoxuron activity resulted from foliar uptake. Results are discussed with reference to field reports of metloxuron use against B. sterilis. L.
Dégradation catalytique du propyzamide déposé sur bentonite
Authors: BASTIDE J. , COSTE C. M. , SABADIE J.
Published: July 2006

La dégradation du propyzamide a étéétudiée après dépôt sur diverses bentonites homioniques. Les meilleures activités sont obtenues avec les bentonite Ag + et Cu++ qui provoquent la dégradation du propyzamide selon un processus en deux étapes. La présence d'humidité provoque l'apparition d'un processus secondaire compétitif.
Absorption and translocation of 14C‐3,6‐dichloropicolinic acid in Cirsium arvense (L.) Scop.
Authors: O'SULLIVAN P. A. , KOSSATZ V. C.
Published: July 2006

Experiments were conducted in a growth cabinet to investigate the absorption and translocation of 14C‐3, 6‐dichloropicolinic acid by Cirsium arvense (L.) Scop. (Canada thistle, creeping thistle), a sensitive species. Applications were made, either to the middle four leaves of 12‐cm‐tall vegetative plants grown under low (40%) and/or high (>95%) relative humidity (r.h.), or to four upper or lower leaves of 30‐cm‐tall flowering plants grown under low r.h. Following application to vegetative plants, absorption and translocation of 14C‐3,6‐dichloropicolinic acid was rapid and was approximately doubled by high r.h. High r.h. increased the amount of radioactivity retained by the treated leaves or translocated to the shoots but did not affect greatly the amount retained in the roots. The herbicide was highly mobile, with over half of that absorbed, translocated out of the treated leaves after two days. The apex accumulated most of the radioactivity, while approximately 8% was recovered from the roots. The absorption and translocation patterns were similar to those reported in the literature for picloram in C. arvense. Absorption of 3,6‐dichloropicolinic acid was greater in vegetative than in flowering C. arvense plants, and placement of herbicide on lower leaves tended to decrease the amount of radioactivity recovered from shoot apex and increase the amount recovered from the roots. Approximately 15% of the applied radioactivity could not be recovered from treated plants by 2 days after treatment.
The influence of water solubility on the movement and degradation of simazine in a fallow soil
Authors: NICHOLLS P. H. , BRIGGS G. G. , EVANS A. A.
Published: July 2006

The movement and degradation of simazine in the field during winter and summer were measured and compared with simulations using a simple model. The model only simulated simazine behaviour closely when water solubility was taken into account. Relationships between water solubility, melting point, soil adsorption and octan‐1‐ol/water partition coefficient indicate that, at agricultural rates of application, water solubility will only have an important influence on behaviour for relatively polar chemicals with high melting points.
Mechanism of action of asulam in celery tissue cultures
Authors: HEWERTSON N. A. , COLLIN H. A.
Published: July 2006

The mechanism of action of the phenylsulphonyl carbamate herbicide (asulam) was examined in celery tissue cultures to see whether the mechanism involved an inhibition of folic acid synthesis. When asulam was included in the nutrient medium, growth of the celery cultures was reduced but not entirely inhibited even at a concentration of 250 μm. Growth was also reduced if a phenylcarbamate herbicide (barban), or sulphanilamide were included in the medium. The addition of folic acid, or 4‐amino benzoic acid, which is a precursor of folic acid, almost totally reversed the inhibitory effect of the asulam and sulphanilamide, but not of barban, whereas the addition of thymidine, methionine, serine or adenine, all of which are formed from folic acid, did not reverse the inhibitory effect of asulam, sulphanilamide or barban. Nevertheless the removal of the growth inhibition of asulam by folic acid or 4ABA suggested the mechanism of action of asulam was similar to that of a sulphanilamide. This mechanism of action in celery cell cultures appears to be similar to that found for asulam in intact plants of a range of species.
Selectivity factors relative to asulam for Senecio jacobaea L. control in Medicago sativa L. II. Metabolism*
Authors: HARPER DELBERT R. , APPLEBY ARNOLD P.
Published: July 2006

Metabolism of 14C asulam applied with surfactant was studied in Senecio Jacobaea L. and Medicago saliva L. Plants were harvested 48, 96 and 144 h after treatment and extracted with acetone. The aqueous residue of the acetone extract was partitioned with ethyl acetate and the 14C activity in the ethyl‐acetate phase, the aqueous phase and the plant residue was determined. A significant amount of 14C activity was not extracted by acetone from either species. This amount increased with time in M. sativa but remained relatively constant in S. jacobaea. More 14C activity was found in the aqueous phase than in the ethyl‐acetate phase in M. sativa while the reverse was true in S. jacobaea. Significantly lower amounts of free asulam were identified in M. sativa than in S. jacnbaea. Still, results of these and previous studies on retention, uptake and translocation do not completely account for differences in sensitivity found in greenhouse and field applications. Other possible explanations for selectivity are discussed.
Effects of application method on the performance of some soil‐applied herbicides. I. Glasshouse experiments
Authors: ADDALA M. S. A. , HANCE R. J. , DRENNAN D. S. H.
Published: July 2006

Chlortoluron, propyzamide, terbutryne and nitrofen were applied to the soil in pots with a rotary atomizer at 301 ha−1, with a conventional hydraulic nozzle at 400 1 ha−1 at several doses, or as discrete 2‐μl drops applied with a microsyringe at 2‐cm spacings. The test plants were Alopecurus myosuroides, Stellaria media, Chenopodium album, Avena fatua, perennial ryegrass and radish. Chlortoluron, propyzamide and terbutryne had the same activities following the rotary atomizer or conventional spray application but the rotary atomizer application of nitrofen was less effective against A. fatua than the conventional spray treatment. Chlortoluron, propyzamide and terbutryne showed appreciable activity applied as drops 2 cm apart at rates equivalent to 2 kg ai ha−1, on plants growing equidistant from the drops, but nitrofen showed no activity under these circumstances.

The activity of chlortoluron was investigated at different soil moisture contents; it was more active when applied to moist soil than to dry soil which was not wetted for at least 10 h. Application method did not affect this response
Growth and patterns of resource allocation in Eupatorium odoratum L. in the secondary successional environments following slash and burn agriculture (Jhum)
Authors: SAXENA K. G. , RAMAKRISHNAN P. S.
Published: July 2006

Biomass, nitrogen, phosphorus and potassium in Eupatorium odoratum L. (Asteraceae), an abundant early successional perennial weed, were studied in seral stages after slash and burn. Increment in individual biomass and nutrient uptake declined with increasing time after fallow. A higher proportion of the available resources was allocated to the supporting organs but a lower proportion to the photosynthetic organ in the older fields compared to recently fallowed fields. The allocation of biomass to reproduction, and also nutrient content, decreased during seral development. However, cost of reproduction to the plants (considered as the proportion of increment in biomass or nutrient uptake during the current growing season) was much higher in the older fields than the younger ones. Growth was adversely affected by low nutrient availability in soil in the recently fallowed fields but the allocation pattern remained unaffected. Biomass was not allocated in the same manner as nutrients. A higher proportion of nitrogen and phosphorus compared to that of biomass and potassium was devoted to reproduction in all the fields.
Response of three winter wheat cultivars to difenzoquat
Authors: PALLETT K. E.
Published: July 2006

The response to difenzoquat of the three winter wheat cultivars, Hobbit, Maris Huntsman and Score is compared. In an experiment in which plants with three to four leaves were sprayed with 0, 1, 2 and 4 kg ai ha−1 difenzoquat Maris Huntsman was most tolerant while Score appeared least tolerant. Difenzoquat reduced the main shoot height and lamina length, and increased tiller number. At the high doses the main shoot was often killed, particularly in Hobbit and Score, which showed stunting and tillering with the 1‐kg dose. DNA synthesis, monitored by 14C‐thymidine incorporation in excised meristematic segments, and 14C‐difenzoquat penetration and translocation were compared in the three cultivars. 1 × 10−4m difenzoquat inhibited DNA synthesis by 7·9, 29·3 and 45·5% in Maris Huntsman, Score and Hobbit respectively. This is likely to contribute to the different responses of Maris Huntsman and Hobbit as 14C‐difenzoquat penetration and translocation were similar. However, there was a greater accumulation of 14C activity in the apical meristem of Score, which is likely to contribute to the greater susceptibility of this cultivar, as is the greater inhibition of DNA synthesis and higher level of spray retention.
A mathematical modelling approach to the study of the economics of controlling Rumex obtusifolius in grassland
Authors: DOYLE C. J. , OSWALD A. K. , HAGGAR R. J. , KIRKHAM P. W.
Published: July 2006

Synthesizing data from several sources, a simplified mathematical model of dock (Rumex obtusifolius) reproduction, growth and competition with grass has been constructed. Using the model, an attempt has been made to study the short‐ and long‐term economic implications of controlling dock infestation in a grassland conservation system by use of the herbicide asulam. The sensitivity of the results has been tested in respect of assumptions about the efficacy of asulam in controlling docks and the economic values attached to grass and dock dry‐matter production. However, given the large number of assumptions necessitated by the limited availability of data and in the absence of any means of validating the model, extreme care is needed in interpreting the results. Nonetheless, while the model cannot be used to derive practical recommendations it can and does provide some useful insights into herbicide control of docks. However, confident economic predictions of the value of controlling docks in grassland await further experimental work on the population dynamics of docks, the factors influencing the effectiveness of herbicides and the nutritive value of docks.
Measurement of phytotoxicity of commercial and unformulated soil‐applied herbicides
Authors: STREIBIG J.C.
Published: July 2006

The relative potencies of analytical‐grade lenacil (99% ai) and its commercial formulation, Venzar® (80% ai), technical‐grade ethofumesate (96%) and its commercial formulation Nortron® (21% ai) were evaluated using oats (Avena sativa L. cv. Selma) as test plant.

In all experiments the dose‐response curves of the pure herbicide and its commercial product were parallel. The average potency of Venzar relative to lenacil, assayed twice in a sandy loam, was 0⋅80 and thus equal to the expected 0⋅80. The average potency of Nortron relative to ethofumesate, assayed in a sandy loam and a loamy sand, was 0⋅25 and close to the expected value of 0⋅21.

The implication of using the technique of parallel‐line assay in herbicide studies is discussed and its potential use in other contexts than the present one is suggested.
Role of temperature in regulating timing of germination in soil seed reserves of Lamium purpureum L.
Authors: BASKIN J. M. , BASKIN CAROL C.
Published: July 2006

Fresh seeds of Lamium purpureum L. were dormant at maturity, and when buried and exposed to natural seasonal temperature changes they exhibited an annual dormancy/non‐dormancy cycle. During burial in summer, fresh seeds and those that had been buried for 1 year afterripened and thus were non‐dormant by September and October; light was required for germination. During autumn and winter seeds re‐entered dormancy, and during the following summer they became non‐dormant again. Dormant seeds afterripened when buried and stored over a range of temperatures, becoming conditionally dormant at low (5, 15/6°C) and non‐dormant at high (20/10, 25/15, 30/15 and 35/20°C) temperatures. Conditionally dormant seeds germinated to high percentages at 5, 15/6 and 20/10°C, while non‐dormant seeds germinated to high percentages additionally at 25/15, 30/15 and 35/20°C. Low temperatures caused non‐dormant seeds to re‐enter dormancy, while high temperatures caused a sharp decline in germination only at 30/15 and 5°C. The temperature responses of L. purpureum seeds are compared to those of L. amplexicaule L.
Residualwirkung von Chlortriazin‐Herbiziden im Boden an drei rumänischen Standorten. II. Prognose möglicher Folgekulturen bei Atrazinrükständen im Boden
Authors: PESTEMER W. , GHINEA L. , RADULESCU VALERIA
Published: July 2006

Von drei Versuchsstationen in Rumänien, die unterschiedliche Klima‐ und Bodeneigenschaften aufweisen, wurden 1982 120 Tage nach Applikation von 3 kg Atrazin ha−1 in Mais (Zea mays L.) Proben aus 0–10 cm Bodentiefe auf ihre Gesamtrückstände und pflanzenverfügbaren Anteile mit einer Wasserextraktions‐ und Biotestmethode untersucht. An einem Standort wurden zudem die gleichen Bestimmungen 3,5 Jahren nach Anwendung von 100 kg AS ha−1 durchgeführt.

In Abhängigkeit von der unterschiedlichen Atrazinverlustrate und der prozentualen Verfügbarkeit bei den drei Standorten konnten 30–120 μg 1−1 Boden an potentiell pflanzenverfügbarem Atrazin ermittelt werden.

In Langzeit‐Biotesten in Hydroponik wurde die Aktivität dieser Konzentrationen auf die für Rumänien wichtigsten Folgekulturen nach Maisanbau—Sonnenblume, Winterweizen, Sojabohne und Lein—überprüft. Die ED50‐ Werte und die Einteilung der Wirkung in fünf Aktivitätskategorien erfolgte mit der Probit‐Analyse, wobei die Sonnenblume mit 22 μg 1−1 die höchste und die Sojabohne mit 78 μg 1−1 die niedrigste Empfindlichkeit zeigte.

Mit Hilfe der ermittelten Verfügbarkeitswerte kann für jeden Standort anhand einer Verträglichkeitsliste abgelesen werden, ob und wie stark Atrazin‐Rückstände mögliche Nachbaukulturen zu schädigen vermögen.
A competition index for Orobanche crenata Forsk effects on broad bean (Vicia faba L.)
Authors: MESA‐GARCÍA J. , GARCÍA‐TORRES L.
Published: July 2006

The influence of broomrape (Orobanche crenata Forsk) infection levels on commercial broad bean (Vicia faba L.) crops was investigated and an equation relating yield losses to O. crenata density was derived. O. crenata growth was weakly and negatively related to the final height or shoot number of the broad bean plant. O. crenata decreased seed yield mainly by reducing the number of pods. The number of seeds per pod was also decreased by O. crenata infection when competition occurred at late‐crop growth stages when most of the pods had already developed. Bean unit seed weight was only weakly affected by infection. Correlation coefficients between O. crenata number and broad‐bean seed yield per plant were significant at P=0·05 and greater than 0·70 in most locations. On average, about four O. crenata per broad‐bean plant decreased seed yield by half. An estimation of the percentage of losses in any field can be calculated from the equation:

%loss = 100 × 0·124 × OcN.

where OcN is the average final number of emerged O. crenata per plant.
Effects of fluazifop‐butyl on shoot growth and rhizome buds of Elymus repens (L.) Gould
Authors: CHANDRASENA J. P. N. R. , SAGAR G. R.
Published: July 2006

A series of glasshouse experiments was conducted to evaluate the activity of fluazifop‐butyl, butyl 2‐[4‐(5‐trifluoromethyl‐2‐pyridyloxy)phenoxy] propionate, against Elymus repens. Foliar applications of doses 0·25–1·0 kg ha−1 consistently gave better control than did soil applications. The most obvious phytotoxic symptoms were chlorosis and necrosis, beginning with the youngest leaves 5–6 days after spraying, which spread to all leaves within 2 weeks. Translocation was measured by defoliating plants at different times after spraying and assessing regrowth and by evaluating rhizome‐bud viability. At low doses (0·125 and 0·25 kg ha−1) translocation to rhizomes occurred mainly between 6 and 48 h. When fluazifop‐butyl was sprayed at a dose range of 0·125–1·0 kg ha−1, at least 90% of the rhizome buds had accumulated a lethal dose within 72 h of spraying. In another experiment, with a dose of 0·25 kg ha−1, 31, 72 and 92% of rhizome buds were found to be non‐viable when sampled 2, 24 and 48 h respectively after spraying. At 1·0 kg ha−1 all the buds had accumulated sufficient herbicide to prevent sprouting 48 h after spraying.
Atrazine metabolism in resistant and susceptible biotypes of Chenopodium album L., Chenopodium strictum Roth., and Amaranthus powellii S. Wats.
Authors: KHAN S. U. , WARWICK S. I. , MARRIAGE P. B.
Published: July 2006

The metabolism of atrazine was studied in resistant and susceptible biotypes of Chenopodium album L., Chenopodium strictum Roth., and Amaranthus powellii S. Wats. Both biotypes metabolized atrazine by N‐dealkylation, hydroxy lation at the 2‐position and conjugation. In addition, binding of mono‐N‐dealkylated atrazine with plant constituents to form nonextractable (bound) residues was also observed. Although parent atrazine levels were similar in the shoots and roots of both biotypes of the three weed species, the resistant biotype in each case contained a higher level of polar conjugates and bound residues in the plant tissues. In contrast, presence of a phytotoxic metabolite, namely 2‐chloro‐4‐amino‐6‐isopropylamino‐s‐triazine, was only observed in the susceptible biotype of the three weed species.
Problems in control of Rottboellia exaltata L.f. in maize in Bukidnon Province, Mindanao, Philippines
Authors: FISHER H. H. , LOPEZ F. , MARGATE L. , ELLIOT P. , BURRILL L.
Published: July 2006

Various methods were tested to control the annual grass Rottboellia exaltata L.f. in maize (Zea mays L.) under small‐farm conditions in Bukidnon Province, Mindanao, Philippines during 1977 and 1978.

No single method was satisfactory. Despite adequate early season control, late‐germinating Rottboellia tillered profusely. By harvest, plots had heavy infestations and were carpeted with seed. At harvest, untreated controls averaged 8·6 t Rottboellia dry matter ha−1 and only half the maize yield of handweeded plots.

The ‘karase’ spike‐tooth harrow, or 0·2 kg paraquat ha−1, effectively removed Rottboellia flushes before maize emergence, but these techniques delayed planting, which can intensify downy mildew disease (Sclerospora sp.). Even though handweeding increased maize yields and decreased Rottboellia dry weights, it is impractical on typical 3‐ to 5‐ha maize farms. Mungbean (Vigna radiata (L.) Wilczek var. aureus), intercropped with maize, suppressed Rottboellia initially. Openings caused by mungbean harvest, however, allowed explosive late‐season weed growth in maize.

Three herbicide treatments were as effective as handweeding: pendimethalin plus atrazine, either banded over the maize row (followed by cultivation), or broadcast; and pendimethalin followed by 2, 4‐D, both broadcast.

In one experiment, low‐cost practices, including weed flush removal, cultivation, or handweeding, provided high net returns, whereas expensive herbicide treatments produced low net returns.

Fertilizer, applied without weed control, increased maize yield 62%. Without fertilizer, weed control increased yield 107%. Combining the two raised yield 167%.
Prediction of Sorghum halepense (L.) Pers. rhizome sprout emergence in relation to air temperature
Authors: SATORRE E. H. , GHERSA C. M. , PATARO A. M.
Published: July 2006

The dynamics of Sorghum helpense (L.) Pers. rhizome sprout emergence was followed in three different crop systems. A simple exponential model relating the number of rhizome sprouts m−2 to accumulated thermal units, calculated as the sum of the daily mean air temperatures above 15°C, provided a good estimate of cumulative shoot emergence populations (r2= 0·93) over all sampling dates between June and January. A good description of the dynamics of shoot emergence in an independent experiment was obtained from the model.

The possible influence of the crop structure and soil water supply in relation to the model fitness is discussed.
Wild oats (Avenu fatua L.) seed dormancy as influenced by sodium hypochlorite, moist storage and gibberellin A3
Authors: HSIAO A. I. , QUICK W. A.
Published: July 2006

Incubation in gibberellin A3 (GA3) or a 1 h immersion pretreatment with 800 mm sodium hypochlorite (NaOCl) both promoted 20% germination of freshly harvested dormant wild oat (Avena fatua L.) seeds that had been imbibed on water for 10 days. GA3 immediately following 1 h NaOCl immersion pretreatment induced maximum germination. Moist storage (MS) after NaOCl immersion pretreatment resulted in less germination on transference of the seeds to GA3, indicating that GA3 responsiveness was lost during MS. These seeds required a repeal NaOCl immersion plus a GA3 treatment to induce maximum germination. However, GA3 still gave maximum germination if the seeds were stored dry after initial NaOCl immersion. Seeds with water‐induced dormancy responded similarly to freshly harvested dormant seeds when treated with NaOCl, MS, or GA3. Seeds afterripened a longer time had a reduced requirement for exogenous GA3 in the breaking of dormancy indicating that the depth of the GA3‐dependent dormancy decreased with duration of after‐ripening.

Dormant dehulled seeds with a brief NaOCl pretreatment germinated about 30% on water but gave maximum germination when incubated on GA3, an effect that persisted even after 21 days of MS. This effect, coupled with the previous findings, suggested that the NaOCl treatment weakened membrane barriers of the seed coat through a scarification‐like effect, similar to the effects of piercing and acid immersion, and thereby produced increased sensitivity to the presence of GA3. The loss of responsiveness to GA3 in NaOCl‐treated seeds during MS may involve the restoration of integrity of the seed coverings, a process occurring only in the imbibed state, and, presumably, most rapidly in freshly harvested, intact seeds.
Use of substituted urea herbicides for weed control in Euphorbia lathyris L., a potential fuel‐producing crop
Authors: GARCIA‐BAUDIN J. M. , LANSAC A. R. , AYERBE L. , TENORIO J. L. , CADAHIA E.
Published: July 2006

Some substituted urea herbicides (chlortoluron, diuron and methabenzthiazuron) were tested for possible use in the cultivation of Euphorbia lathyris L. Diuron showed high phytotoxicity for this species, which was tolerant to chlortoluron and methabenzthiazuron. In preliminary experiments two triazine herbicide (atrazine and simazine) were also used, but both were so toxic to E. lathyris that their use was not continued beyond this stage.

In glasshouse experiments, chlortoluron showed slight phytotoxicity to E. lathyris but this did not appear in field experiments. Both chlortoluron and methabenzthiazuron were very efficient against weeds which were present and significantly increased yield of E. lathyris in comparison with unweeded plots. The poor competitive ability of E. lathyris against weeds was confirmed.
Effect of chlorfenprop‐methyl, flamprop‐isopropyl and benzoylprop‐ethyl on 14C2 fixation in Avena fatua L., Triticum aestivum L. and Hordeum vulgare L.
Authors: BERGMANNOVA EVA , TAIMR L.
Published: July 2006

The effect of chlorfenprop‐methyl, flampropisopropyl and benzoylprop‐ethyl on 14CO2 fixation was followed in wild oat (Avena fatua L.), barley (Hordeum vulgare L., cv. Ametyst), and wheat (Triticum aestivum L., cv. Mironovská). Experimental plants were exposed to a 14CO2‐enriched atmosphere in a special apparatus 2 h, 1, 3, and 9 days after the herbicide treatment.

Chlorfenprop‐methyl already inhibited 14CO2 fixation in wild oat plants 2 h after the treatment. 14C‐metabolite transport to the roots was strongly decreased. Both 14CO2 fixation and 14C‐metabolite level in the roots were significantly depressed in A. fatua when compared with untreated plants at the last sampling time. 14C incorporation into starch was inhibited from the first day after treatment, and on day 9 was lowered more than ten fold in treated plants.

Flamprop‐isopropyl inhibited 14CO2 fixation in wild oat plants from day 3 after treatment, but benzoylprop‐ethyl not until day 9. Both herbicides also decreased 14C incorporation into starch in A. fatua. Chlorfenprop‐methyl also slightly decreased 14CO2 fixation in barley on day 9. However, assimilate transport into the roots and 14C incorporation into starch were not affected. Flamprop‐isopropyl inhibited 14CO2 fixation in barley plants only on the first day after treatment, and assimilate transport was also reduced. By contrast, no differences from untreated plants were found at the end of the experiment. Benzoylprop‐ethyl did not decrease either 14CO2 fixation or assimilate transport to the roots in wheat, but it inhibited starch synthesis. Atrazine depressed 14CO2 fixation in wild oat plants by 91%, in wheat plants by 99% compared with untreated plants. Assimilate transport into the roots was also strongly inhibited. In contrast to atrazine, the effect of chlorfenprop‐methyl, flamprop‐isopropyl, and benzoylprop‐ethyl on CO2 fixation seems to be secondary.
Effects of three herbicides used to control volunteer ryegrass on tillering and seed yield of two second year perennial ryegrass crops
Authors: OSWALD A. K.
Published: July 2006

Atrazine, chlorpropham and diuron gave excellent control of volunteer perennial ryegrass seedlings and reduced vegetative tillers of perennial ryegrass grown in the glasshouse and for seed in the field. However, there was no compensation in terms of the fertile tillers or seed weight during the second year. The results suggest that the lack of positive effect on seed yield may be due to direct effects on the crop from the residual herbicides.
Mapping of atrazine resistance for Amaranthus retroflexus L. in Hungary
Authors: SOLYMOSI P. , KOSTYAL S.
Published: July 2006

The study extending over all sixteen counties of Hungary has shown atrazine resistant biotypes of Amaranthus retroflexus L. to grow not only in and around maize monocultures but also in rotationally grown maize and even along highways and ruderal areas. In the present study made in 1983 resistant A. retroflexus was found in five counties (Bács‐Kiskun, Csongrád, Hajdu‐Bihar, Nógrád and Szabolcs‐Szatmár) where Hartmann recorded it as absent in 1976. In addition, resistant populations were also found in the counties of Szolnok and Veszprém. The area in which populations of A. retroflexus have developed resistance to atrazine therefore appears to be extending.
Effects of isoproturon in the rhizosphere of wheat
Authors: MUDD P. J. , GREAVES M. P. , WRIGHT S. J. L.
Published: July 2006

In a field experiment, isoproturon (as Arelon) applied to soil at 2·5 kg ai ha−1 caused variable effects in the rhizosphere of winter wheat. These included transient increases and decreases in the number of bacterial and fungal propagules. No changes in soil levels of NH4+‐N, NO2−‐N, NO3−‐N or PO43− were detected. Similar results were recorded with wheat grown in pots and in laboratory‐incubated soil.

Arelon (1–60 μg ai ml−1) did not affect pure cultures of bacteria but at the highest concentration (approximating to fifty times field rate) inhibited growth of some fungi. The value of laboratory and field experiments for studying effects of pesticides on micro‐organisms is discussed. The results suggest that Arelon, in practical use, is unlikely to have harmful effects on the micro‐organisms or fertility of soil.
Dégradation catalytique de carbamates herbicides déposés sur bentonites homoioniques. III. Cas du phenmédiphame et du desmédiphame
Authors: Et J. SABADIE , COSTE C. M.
Published: July 2006

Résumé: Summary: Zusammenfassung

La dégradation chimique en phase sèche du phenmédiphame et du desmédiphame a étéétudiée à température ambiante sur diverses bentonites homoioniques (Fe3+, Mn2+, Cu2+, Ag+ et Zn2+). Le cuivre, l'argent et le zinc sont actifs. Le schéma général du processus de dégradation proposé indique que seule la fonction carbamate intercycles est hydrolysée selon un mécanisme type E1cB (formation d'isocyanate intermédiaire).

The chemical degradation of phenmedipham and desmedipham on various homoionic bentonites (Fe3+, Mn2+, Cu2+, Ag+ and Zn2+) was investigated at room temperature. In these conditions. Cu2+, Ag+ and Zn2+ were the most active cations. The chemical degradation pathway proposed only indicates the hydrolysis of the carbamate function located between the two aromatic nuclei according to the E1cB mechanism (isocyanate is involved as intermediate).

Katalytischer Abbau von Carbamatherbiziden auf homionischen Bentoniten. III. Phenmediphan und Desmedipha

Es wurde der chemische Abbau von Phenmedipham und Desmedipham auf verschiedenen homoionischen Bentoniten (Fe3+, Mn2+, CU2+. Ag2+ und Zn2+) bei Zimmertemperatur untersucht. Unter den gegebenen Versuchsbedingungen waren Cu2+, Ag+, und Zn2+, die aktivsten Kationen. Es wird angenommen, dass der chemische Abbau auf einer Hydrolyse der Carbamatfunktion zwisehen den zwei aromatischen Ringen beruht und einem Mechanismus vom Typ E1cB (Bildung von intermediärem Isocyanat) folgt.
Dégradation catalytique de carbamates herbicides deposés sur bentonites homoïoniques. IV. Cas du carbetamide
Authors: Et J. SABADIE , COSTE C. M.
Published: July 2006

Résumé: Summary: Zusammenfassung

En phase sèche à 20° C, le carbétamide peut se dégrader lentement sur divers supports argileux homoïoniques (Bentonite Prolabo, Montmorillonite K 10; Cu++, Zn++, Fe+++). Le Cuivre présente la meilleure activité. Un processus de dégradation suivant deux voies parallèles a été mis en évidence au cours de la première étape. La sélectivité observée est influencée par la méthode d'imprégnation, la nature du support et du métal. A température supérieure (80° C), on observe sur gel de silice et Montmorillonite K 10 un processus plus complet de dégradation qui permet de confirmer la formation d'isocyanate intermédiaire lors de l'hydrolyse de la fonction carbamate du substrat.

Surface catalysed degradation of carbamate herbicides on bentonites. IV. Carbetamide

The chemical degradation of carbetamide on various homoionic clays (Bentonite Prolabo, Montmorillonite K 10:Cu++, Zn++, Fe+++) (was investigated at room temperature. The kinetics of the reaction was generally slow; however, copper was the most active metal. The first stage of the chemical process included two ways of degradation. The selectivity of the conversion was influenced by the impregnation technique, clay type and exchange metal. At a higher temperature (80° C) on silica gel and montmorillonite K 10, the whole process of degradation was observed which indicated that isocyanate is involved as an intermediate in the carbamate hydrolysis function.

Katalytischer Abbau von Carbamaten an Bentaniten. IV. Carbetamid

Der chemische Abbau von Carbetamid an verschiedenen homoionischen Tonmineralen (Bentonit Prolabo, Montmorillonit K 10; Cu2+, Fe3+) wurde bei Zimmertemperatur untersucht. Die Reaktion war allgemein langsam, aber Kupfer war am wirksamsten. Die erste Stufe des Abbaus besteht aus zwei Wegen, worüber die Art der Imprägnierung, das Tonmineral und die ausgetauschten Metalle entscheiden. Bei höherer Temperatur (80° C) konnte an Silicagel und Montmorillonit K 10 der gesamte Abbauprozess beobachtet werden, wobei sich zeigte, dass Isocyanat als Zwischenprodukt der Hydrolyse von Carbamat auftritt.