In summer 1977 a random survey was made of 2250 fields on 1153 farms selected throughout the United Kingdom. Wild oat, Avena spp., was surveyed in all countries; black grass, Alopecurus myosuroides, was surveyed in England and Wales; and couch grass, including Agropyron repens and other perennial grasses, in Scotland and N. Ireland.Wild oat was reported by farmers on 95 % of farms in England, 34 % in Wales, 65% in Scotland and 30% in N. Ireland; the areas of infestation in the different countries were 67, 13, 37 and 16 % respectively. The majority of wild oat was A.fatua. Only 6 % of the cereal area of U.K., including sprayed and unsprayed fields, contained more than one wild oat seed head/m 2 (10000/ha), the majority had less than one/20 m 2 . Black grass was reported on 50 % of farms in England (22 % of cereal area) mainly in East and South, and on 2 % of farms in Wales. Couch grass occurred on 92 % of farms in Scotland and 68 % in N. Ireland: areas of infestation were 88 and 67 % respectively. Most of the infestations of all three weeds had been present for longer than 5 years.Most farmers intended to eliminate or reduce wild oat and few proposed to hold the weed at its present level or do nothing. [Herbicides were used against wild oat on approximately half of the infested area in England and Wales, with proportionately more use in Wales and much less in Scotland and N. Ireland. A third of the black grass infested area of England was treated with a herbicide. There was little spraying against couch grass in Scotland and N. Ireland. Details of dose, time of application and mixing of chemicals were obtained. Wild oat was subsequently found on most of the area treated against this weed, similar observations were made of black grass and couch grass. Most farmers considered herbicide performance good or excellent and those in East and South England believed wild oat to be decreasing as a problem; farmers elsewhere thought the problem to be increasing.Hand pulling of wild oat (roguing) had occurred on only one tenth of the infested area but a greater area was intended to be rogued after the survey visit. Much of the land that had been rogued was found subsequently to contain few wild oats.The survey provided information on associations between weed presence, soil type and cropping system, the types of herbicide used and farmers' impressions of their performance. Comparisons are made with previous surveys in 1972, and information on the disposal of the 1976 crop of straw and on types of cultivation used in different regions is provided. The implications of the results are discussed.
The Following factors infiucnciiiff the selectivity of di-allate against Avena spp. in spring wheai and barley have been investigated in seven field experiments: (a) depth and degree to which the herbicide is mixed wilh the soil, (b) time of application ofllie herbicide relative to sowing the crop, (c) implement used lo incorporate the herbicide with ihe soil, (d) depth of germination of the Avena spp.Di-allaie and tri-allate incorporatod relatively tU-eply before drilling the crop controlled Avena spp. much more effectively than when incorporaied shallowly by chain-harrowing after drilling, but the pre-drilling treatments were also more toxic to the crop.In wheat, di-atlate incorporated shallowly after drilling was slightly more selective than when incorporated more deeply before drilling but in barley there was no evidence to favour either time of application. Pre-drilling treatments incorporated by a rotary cultivator were a little more selective to both crops than those incori^orated by springtine harrows.Tri-allate was more selective than di-allate, in wheat, when incorporated before drilling the crop. There was no evidence regarding its selectivity as a post-drilling treatment.The initial distribution of the herbicide in the soil, after incorporation by; (a) spring-tine harrowing once, (b) rotary cultivating once or twice, or (c) chain harrowing once, was meastired in one experiment by a fluore.scent tracer technique. The results showed that ordinary' farm implements give a very uneven distribution (both vertical and lateral) of herbicide in the soil.In the field, di-allate and tH-allate incorporated with the soil shallowly after drilling proved to be less selective and less active than similar treatments in the glasshouse. It is suggested that the reduced selectivity of these treatments in the field is due to loss of herbicide by vaporization and retention ofthe herbicide by thesoilunder dry conditions. The importance ofthe various factors influencing the selectivity of di-allate and triallate in the field is discussed in the light of the results of these experiments and those of other research workers (particularly Parker. 1963). Essais de plein champ sur la pkytotnxkiU selective du di-allate envers les Avena spp. dans le ble et I'orgeLes factours suivants. qui inHueneent I'activit^ du di-allate envers les .4wn(iapp., et sa selectivity vis-a-vis dc Forge et du bl^ de printemps, ont ^t6 etudi^s dans 7 essais de plein champ: (a) La profondeur et le degr^ d'incorporation de l'herbicide au sol, (b) L'^poque du traitement par rapport a la date du semis de la culture, (c) L'outil utilise pour incorporcT i'herbicide au sol, (d) La profondeur a laquelle ont gertn^ ies semences d'Avena spp.Le di-allate et le tri-allate, incorpor^s avant le semis a une profondeur rclativement grande, ont permis une neutralisation des Avena spp. beaucoup plus efficace que celle obtenue par une incorporation superficielle au moyen d'une herse apres le semis, Toutefois le traitement avant le semis a ^t6 plus prejudiciabie a la culture...
Summary. The phytotoxicities in a number of soils of lenacil, linuron, prometryne and simazine to two indicator plants were determined in field and glasshouse experiments. The results were compared with estimates of the adsorption capacity of the soils obtained by two methods using dimethylaminobenzaldehyde as a model adsorbate. The possible influence of other soil properties was also considered. One of the adsorption measurements had some predictive value for glasshouse behaviour but was not markedly superior to soil organic carbon content for this purpose. None of the factors studied was usefully correlated with field performance. Results from field experiments in spring were poorly correlated with those from similar experiments in autumn. Neither set of field results related closely to those obtained in the glasshouse. It is concluded that the influence of climate was more important than that of soil type. La phytotoxiciti de quelquts herbicides dans des experiences en pots et en plein champ, en relation avec les propriétés du sol
The volatility of tri‐allate from different formulations when mixed with 2 soils containing water at 2%, 6% and field capacity was estimated in the laboratory. Volatility increased with increasing water content in each case. It was generally highest from an emulsifiable concentrate and lowest from a granule formulation with that from unformulated tri‐atlate intermediate. In a greenhouse experiment rates of loss of tri‐allate from a dry soil were similar for both emulsifiable concentrate and granule formulations, but from a wet soil and an aluminium foil dish losses were much greater from the emulsifiable concentrate. The persistence of trii‐allate from granules applied in the field was virtually the same for granules containing 2.5, 5 or 10% active ingredient.
R6sum^: ZusammenfassungBlaekgrass {Alopecurus myosuroides Huds.) was controlled by 2 kg/ha of metoxuron in glasshouse trials while winter wheat, cultivar Cappelle Desprez, tolerated 4 kg/ha. Blackgrass was controlled by 1-2 kg/ha of chlortoluron. Winter wheat previously damaged by freezing was injured by 2-5 kg/ha of chlortoluron applied at an early stage. Seedlings not exposed to freezing were not damaged by 2-5 kg/ha applied at the 4-and 5-leaf stage.Breakdown of chlortoluron and metoxuron in the soil was attributed, in part, to microbial action. More than one-third of the chlortoluron applied at 2 kg/ha disappeared in 6 weeks when applied in early spring while one half disappeared in 3 weeks when applied 2 months later. The bioassay, used to determine the amount of chlortoluron or metoxuron in the soil, was found to be adequate for metoxuron in only one of three soils.The bioassay results, for both herbicides, were affected by the addition of calcium carbonate to the soil, by sterilization of the soil, and by leaching. In comparisons of results in two sandy loams and a clay loam, the observed differences could not be altogether accounted for by diflerences in pH nor by changes in adsorption of metoxuron. When perennial ryegrass was grown in sandy loam, and treated with metoxuron before or after emergence, different watering regimes did not give any difference in weight of top growth.
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