摘要:

Summary:Large losses in grain yields due to weed competition were found in studies conducted in irrigated dry seeded rice at Gezira Research Station, Sudan. These losses could exceed 50%. Weed competition lowered panicle number per unit area by 37%, number of filled grains per panicle by 13%, and weight of 1000 grains by 4%. Tillering was the critical growth phase most affected by weed competition.Grain yields were increased as number of hand weedings increased. The best yield (4.1 t/ha) was obtained from 3–4 weedings carried out at 15, 30, 45 and 60 days after rice emergence.Oxadiazon (0.5 kg/ha) gave good residual weed control of the dominant weed species,Phyllanthus niruriL.,Leucas urticifoliaL.,HeliotropiumF.W.Andr. andEchinochloa colona(L.) Link, for 6–7 weeks. The combination with continuous flooding from 6 weeks after rice emergence gave excellent weed control during the entire season, and comparable or even better yields than frequently weeded r

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1981.tb00118.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Summary:Effects of glyphosate, paraquat, trifluralin and atrazine on activities of dehydrogenase, phosphatase and urease in one soil were measured. Only glyphosate at 21.6 kg/ha was found to inhibit the enzyme activities and generally the results were not statistically significant. Enzyme activity associated with micro‐organisms proliferating in soil supplemented with lucerne meal was similarly not affected by the herbicides. Interpretation of results from enzyme activity measurements in soils treated with herbicides is discussed. It is proposed that effects of natural stress can be used to judge the relative importance of herbicide induced chang

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1981.tb00119.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Summary:Linuron (0.21 and 0.28 kg/ha) and linuron + MCPA (0.21+0.56 kg/ha) in a tank mixture with field rates of barban, difenzoquat and flamprop‐methyl reduced the phytotoxicity of these herbicides toAvena fatua. When linuron was applied immediately following or 6 days after theA. fatuaherbicides no reduction in phytotoxicity toA. fatuaoccurred, suggesting that the antagonism may be occurring as a result of physical or chemical incompatability when the herbicides are mixed together. The possibility of obtaining broad‐spectrum weed control with one trip over the field by applying linuron and one of these wild oat herbicides separately but at the same time using a double‐boom, double‐tank system deserves evaluation. When linuron was applied in a tank mixture (0.21 and 0.28 kg/ha), immediately after, or 6 days after diclofop‐methyl (0.70 kg/ha), there was no reduction ofA. fatuacontrol, and wheat tolerance to the tank mixture was good. This tank mixture offers potential for control under field conditions ofA. fatuaand some broad‐leaved weeds in one spray operation. Linuron + MCPA (0.21+0.56 kg/ha) in a tank mixture severely reducedA. fatuacontrol with diclofop‐methyl. No loss of phytotoxicity toFagopyrum tataricumoccurred when theA. fatuaherbicides tested were tank mixed with linuron or linuron + MCPA.Lutte contreAvena fatuaetFagopyrum tataricumavec des mélanges extemporanés de linuron ou de linuron + MCPA et des applications successives de linuron et d'herbicides de postlevée acti

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1981.tb00120.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Résumé:Par des observations sur la germination dans différentes conditions et sur le développement végétatif en conditions non compétitives, les auteurs comparent des biotypes sensibles et résistants de quatre espèces chez lesquelles on a découvert des populations résistantes:Chenopodium album, Amaranthus retroflexus, Solanum nigrumetPolygonum lapathifolium. Malgré des niveaux de signification différents les résultats indiquent un meilleur développement végétatif des plantes sensibles, Cependant, ces données peuvent être modulées selon les conditions de croissance. Par ailleurs, les valeurs élevées des variances des caractères mesurés traduisent une hétérogénéïté très importante, au moins dans les lots sensibles. En revanche, les semences des plantes résistantes dePolygonum lapathifoliumet, dans une moindre mesure, d'Amaranthus retroflexusgerment plus facilement aux basses températures. A la lumière de ces données les auteurs discutent les avantages que peuvent conférer ces caractéristiques aux différents lots, mais surtout soulignent la nécessité de considérer chaque espèce séparément et de prendre en compte la nature des génotypes comparés. Enfin, il est difficile, à partir de telles donnés et tant que l'on ignore précisément le déterminisme de la résistance, d'en déduire dans les stations d'origine et en l'absence de traitement, une moindre valeur

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1981.tb00121.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Résumé:Des études d'adsorption et de dégradation d'analogues du propyzamide [dichloro‐3,5‐N‐(dimethyl‐1,1 propynyl‐2) benzamide] dans différents sols ont été réalisées. Une bonne corrélation entre adsorption et teneur en matière organique des sols a été trouvée. Cette adsorption est reliée linéairement à un paramètre hydrophobique (coefficient de partage octanol — eau). Par contre la dégradation dans différents sols de ces composés ne montre pas de relation simple avec la nature des sols ou avec la structure chimique des composés. L'importance de ces phénomènes sur les résu

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1981.tb00122.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Summary:Observations made on the hyperparasitism ofViscum loranthiElmer on the parasitic weedScurrula cordifolia(Wall.) G. Don in the Sivalik Hills suggest that the hyperparasite is providing effective biological control of the latter. Moreover, as the hyperparasite appears to attack only mistletoes, it can probably be introduced with safety into other localities whereS. cordifoliais spreading.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1981.tb00123.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Summary:A number of 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. The evaluation was done under standardized conditions. The influence of the herbicides on the plants was evaluated by using the following bioassay methods: percentage mortality and the percentage dry mass difference between the test plants and the control 10 days after treatment.Recommendations are made as to which herbicides could be used most effectively on problem weeds post‐emergence in maize fields. The developmental stage (age) at which each herbicide is most effective, has been determi

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1981.tb00124.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Summary:The responses of onion (Allium cepa).Veronica persica, Matricaria matricarioidesandStellaria mediato post‐emergence applications of methazole were measured in field and glasshouse experiments.Stellaria mediawas the most susceptible species andV. persicathe 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

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1981.tb00125.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY