摘要:

Summary:The occurrence of noxious weed species on roadsides and adjacent farmland was studied in ten agricultural areas throughout Victoria. Australia. The presence of noxious weeds in both situations was influenced by the other vegetation present and was reduced by tree cover on roadsides or improved pastures on the farmlands. Most of the noxious species recorded were found both on the roadsides and on farmland. The shrubs (e.g.Acacia armataR. Br.,Crataegus monogynaN.J. Jacq.,Genista linifoliaL. andLycium ferocisinnumMiers) were more abundant on roadsides, and usually occurred only as hedges on farmland.Hypericum perforatumL. was recorded only on roadsides since this species is now generally controlled in farmland by pasture improvemenl.Because noxious weeds did not appear to invade better managed farmland the significance of their control on roadsides should be reassessed. Where control on roadsides is considered to he necessary, better suppression should be achieved by maintaining good tree and grass cover.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01521.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Two bio‐assay methods for determining the amount of propyzamide in soil were evaluated and compared with analysis by gas‐liquid chromatography. The root length assay with flax (Linum usitatissiimumL.) as well as the more time‐consuming shoot assay with canary grass (Phalaris canariensisL.) were sufficiently accurate when carried out under favourable growing conditions. However, gas‐liquid chromatography wilh electron‐capture detection was more sensitive to low concentrations of propyzamide and also to moderate concentrations when the soil organic matter content was highAs the organic matter content of the soil increases, propyzamide becomes less available to plants. The rate of decline does not seem to be influenced by Ihe type of soil.A few months after autumn treatment the rate of disappearance of propyzamide was fairly high in the field, even at low temperatures. The rates of decline under summer conditions were in Ihe expected range.When selecting the next crop, it should he taken into account that propyzamide residues may be present in the soil for several months after ap

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01522.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:The persistence of [14C]2,4‐D at a rate equivalent to 1 kg/ha was studied in the laboratory on a heavy clay and a sandy loam at 85%of field capacity and 20°C both alone and in the presence of 1 kg/ha dicamba, dichlorprop, difenzoquat, TCA, and 2,4,5‐T. The persistence of 2,4,5‐T was also monitored in both soils under the same conditions in the presence and absence of [14C]2,4‐D. All soils were extracted at weekly intervals using aqueous acidic acetonitrile and analysed for [14C]2,4‐D remainining radiochemical techniques. The extracts containing 2,4.5‐T were additionally analysed gas chromatographically for that herbicide.In each soil type the half‐life of the 2,4‐D was similar regardless of whether applied singly or in combination with the five herbicides tested. Similarly, [14C]2,4‐D did not affect the breakdown of 2,4,5‐T in either soil type.The persistence of tri‐allate (1·5 kg/ha) and trifluralin (0·75 kg/ha) both singly and in combination were compared using small field plots at two locations in Saskatchewan. Applications were made during May of 1977 and 1978 and the plots were sampled and analysed for herbicide(s) remaining after 10 and 20 weeks, respectively. The results indicate that within experimental error the loss of both tri‐allate and trifluralin from the plots treated with the mixture was the same as from plots treated wit

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01523.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:In glasshouse experiments foliar application or14C‐labelled herbicides to water hyacinth plants at the 4‐leaf stage indicated that amilroie transport from the treated leaf blade was faster and greater than 2.4‐D. but a little less than asulam. From the treated leaf 14·2, 25·9. 39·7. 44·5 and 51·8% of the recovered14CNamitrole was translocated at intervals of 6 h. and 1. 3. 6 and 12 day., respectively. Both xylem and phloem transport of asulam and amitrole was evident, whereas 2.4‐D moved only from ‘source to sink’.Movement of the herbicides from the mother to the connected daughter plant or vice versa was dependent upon the size of the latter. Maximum transport of these herbicides in either direction took place at the 2‐leaf stage of daughter plants. With any increase or decrease in the number of leaves on daughter plants, the transport of herbicides was reduced. As an exception, daughter plant to mother plant movement of amilroie was maximum at the 1‐leaf stage.After extraction, fractionation and TLC separation of foliage applied14C‐2.4‐D 76–4 and 72·1% of the radioactivity was detected in the chloroform phase of the leaf extract at 3 and 6 day intervals, respectively.In another pot culture experiment, it was observed that after spraying the mother plants with 2.4‐D‐amine at 0–75 kg/ha the connected daughter plants at 1 to 4‐leaf stages werckilled if the culture solution was contaminated while spraying, or by dying leaves. When contamination was totally avoided, the connected but unsprayed daughter pl

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01524.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Experiments investigating the effect of weed density on the yjeld of a wheat crop at three levels of applied nitrogen were conducted in north‐western Victoria. Australia, during 1970. There were five sites, each infested with a pure stand of one of the following annual broad‐leaved weed species:Lithospermum arvense, Brassica tournifortii. Lamium amplt'xicaule, Amsinckia hispidaandFumaria parviflora.At the three‐leaf stage of crop growth, the weed populations were systematically thinned with a specially developed spray boon) (which is described) to give a range of weed densities in competition) with the crop.The relalionship between dry matter production and population density for all but one weed species was curvilinear, but the degree of curvature was small and competition in the wheat crop was linear for four of the five weed species. There were large differences in the competitive ability of individual weed species and these have been described by regression equations. Applied nitrogen increased wheat yields at all sites but weed competition was not affected.The use of these grain yield‐weed density relationships in predicting crop losses from weed competition is di

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01525.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Mixed infestations ofAlopecurus myosuroidesandArena fatuagrowing in wheat were controlled individually or together in three experiments. Difenzoquat and ciofop‐isohutyl were applied at the early tillering or early stem extension stages of the crops. Early control of both species resulted in significantly higher yields than later control, even though weed emergence was incomplete at the early applications. Herbicides, re‐applied at the second date, improved the control of wild‐oats hut not of black‐grass; yields were not enhanced by this second application Halving the dose of herbicide gave little reduction in weed control or crop yield at the early date, but there was a greater response to dose with the later application. Yields were lower where only one weed was controlled. This work shows the need for broad spectrum control early in the life of the crop to safeguard yield where black‐grass, and wild oats occur together in larg

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01526.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Wettable powder formulations of simazine, metribuzin and linuron and a suspension concentrate of simazine were sprayed on to soil particles which were either at a water content equivalent to pF 2·5 or air dry. Air dry samples were then wetted to pF 2·5 immediately or after 24 h. Soil solutions were removed using a pressure membrane apparatus at intervals up to 96 h after wetting. In each case the concentration in soil solutions expressed after 96 h following application to wet soil, or dry soil wetted immediately, were close to those predicted on the basis of Freundlich adsorption isotherm data obtained in slurry equilibrium conditions. There were, however, some differences after shorter periods.Concentrations were always lower in solutions obtained from air dry soil that was not wetted for 24 h. After 96 h simazine and metribuzin concentrations were about 50% of those obtained following application to wet soil, while that of linuron was about 25%. Differences of this size may be large enough to affect mass transfer phenomena and phytotoxicity. It seems likely that suspension of these herbicides sprayed in formulations on to wet soil dissolved in soil water at least as fast as would be predicted theoreticall

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01527.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Research conducted in El Salvador, Central America, demonstrated that an interval of 3 days between application of glyphosate and tillage was sufficient to cause 90% reduction in purple nutsedge (Cyperus rotundusL.) plants, while delays of 11–23 days generally gave slightly less reduction. à second application to the same plots 35 days following tillage resulted in more than 90% reduction with all intervals. Approximately 3 months after the initial treatment, tuber numbers had been reduced to half the original population. Germination of the remaining tubers was reduced by more than 50%.Glyphosate applied during the dry season caused an average of 79% reduction in plant numbers compared with 88% in the rainy season. However, in the dry season, the remaining plants had no competition from other weeds and after 5 months there was only à 40% reduction in nutsedge population. During the rainy season, 1, 2 and 3 kg/ha were equally effective, but 1 kg/ha was not sufficient in the dry sea

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01528.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Summary:Tank‐mixtures of selective herbicides were evaluated for 2 years on field‐grown sugarbeets under two weed flora situations: (a) mixed floras of broad‐leaved and grass weeds and (b) weed floras of broadleaves grown beyond their stages of greatest sensitivity to herbicides. In these situations single herbicides usually fail to provide satisfactory post‐emergence weed control in sugarbeets.Of several tank‐mixtures, which could be devised for use in the first situation, ethofurnesate + Betanal AM 11, diclofop‐methyl + Betanal AM 11 and diclofop‐methyl + metamitron gave synergistic phytotoxicity to sugarbeet seedlings. Synergism in weed control, becoming apparent by an accelerated appearance of the herbicidal effects, was obtained with the mixture alloxydimeton + Betanal AM 11. This mixture was not phytotoxic and appears to be the most efficient for simultaneous control of broad‐leaved and grass weeds.From trials in the second situation it became apparent that the activity of metamitron, which was reduced on older weeds, could be restored by mixing with a non‐phytotoxic oil or a low dose of Betanal AM 11. These mixtures should be useful when growth of sugarbeets has been retarded by carried‐over herbicides,

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01529.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Résumé:Divers aspects de la biologie du liseron sont abordés dans ce travail à travers l'étude comparative de populations d'origine française et espagnole. Le poids des semences, la caryologie, les résultats del'électrophorése des protéines séminales solubles, la morphologic foliaire et l'aptitude à la floraison, ont été les caractères utilisés. L'observation des plantes cultivées ensemble à Madrid et la comparaison des électrophorégrammes ont permis de proposer un schéma de différenciation intraspécifique chezConvolvulus arvensisL., en se fondant principalement sur l'influence de sa répartition géographique, facteur rendant bien compte des variations enregistrées. Ce phénomène introduit un élément supplémentaire de variation pouvant affecter la réus

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1979.tb01530.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY