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Notes: Summary. A series of adsorption experiments was carried out in order to determine if there was significant competition for adsorption sites between diuron and water. Adsorption of diuron was much lower on hydrophilic materials such as cellulose, chitin, aluminium oxide and a soil mineral fraction than on the less hydrophilic ion exchange resins, lignin, carbon and a soil organic fraction. Methylation with methanolic HCL or diazomethane increased adsorption by the soil organic material, but methylation with dimethyl sulphate did not.The soil mineral fraction adsorbed considerably more diuron from petroleum spirit solution than from aqueous solution, but the organic matter preparation adsorbed more from aqueous than from petroleum solution.It was concluded that there is competition between water and diuron for adsorption sites and that diuron is a more effective competitor at soil organic matter surfaces than at soil mineral matter surfaces. Observations sur la relation entre l'adsorption du diuron el la nature de l'adsorbant

Notes: Summary. Model adsorbents were prepared by treating cellulose phosphate powder with a series of alkyltrimethylammonium compounds in which the size of the alkyl group was varied from C8to C18. The adsorption of linuron, atrazine and EPTC by these materials was found to increase logarithmically with increasing chain length. The extent of the adsorption was large compared with the adsorption of these herbicides by a humic acid and by a preparation made by removing the bulk of the inorganic constituents of a peat soil with a mixture of HCl and HF. Since soil organic matter is thought to contain alkyl groups, it is concluded that the possible influence of such groups should be considered in any discussion of the mechanisms involved in the adsorption of organic molecules by soils.Adsorption du linuron, de I'atrazine de l'EPTC par des adsorbants de la série aliphatique et des préparations organiques de sol

Notes: A long-term field experiment was established in 1967 to measure the persistence in soil of paraquat dichloride applied annually either as a single dose of 4–48 kg/ha or in four separate doses of 1·12 kg/ha. From 1969 the treatments were split so that the herbicide was applied (a) to the soil surface, (b) to living vegetation. From 1970 to 1972 inclusive, half of each plot receiving four applications per year was rotary cultivated shortly after each spraying to study whether incorporation influenced persistence. Analysis of soil samples taken to a depth of 36 cm in 1971 and 1973 showed that essentially all the applied paraquat was still present. Most of the paraquat was found in the upper 5-cm layer but significant amounts had reached the 25–36-cm layer. In a supplementary laboratory experiment soil taken from the plots and from two other fields was incubated with paraquat at concentrations equivalent to c 50, 100 and 150% of the ‘strong adsorption capacity’. The reduction in paraquat extracted by saturated NH4Cl ranged from 10 to 35% over a period of 17 weeks showing that the microflora of these soils were capable of degrading paraquat slowly if at all. It is concluded that paraquat may be broken down only slowly if at all in the soil under Soil conditions. Persistance à long terme du paraquat dans un limon sableux.Une expérience au champ de longue durée a été mise en place en 1967 pour évaluer la persistance dans le sol du paraquat dichlorure appliqué chaque année, soit à la dose unique de 4,48 kg/ha, soit en 4 doses séparées de 1,12 kg/ha. Depuis 1969, les traitements ont été divisés, l'herbicide étant appliqué (a) soil sur le sol (b) soit sur la végétation. De 1970 à 1972 inclus. la moitié de chacune des parcelles recevant quatre applications par an, a été travailée au rotavator peu de temps aprés chaque traitement, pour étudier I'inlluence de l'incorporation sur la persistance. L'analyse d'échantillons de sol prélevés à une profondeur de 36 cm en 1971 et en 1973 a montré que pratiquement tout le paraquat appliquéétait encore présent. La plus grande partie du paraquat a tit trouvfée dans 5 couche des 5 premiers centimétres mais de quantités significatives avaient atteint le niveau 25–36 cm. Dans une expérience supplémentaire au laboratoire, le sol prélevé dans les parcelles traitées et dans deux autres champs a été mis à incuber avec du paraquat a des concentrations équivalents à 50, 100 et 150% de la ‘capacitéélevée d'ad-sorption’. La réduction du paraquat extrait par NH4Cl saturé s'est étundue de 10 à 35% pour une période de 17 semaines, montrant que la microflore de ces sols était capable de dégrader lentement, sinon pas du tout, le paraquat. II en est conclu que le paraquat, si tani est qu'il puisse etre dégradé dans le sot, ne l'est seulement que lentement dans des conditions de plein champ. Langzeit-Persistenz von Paraquat in einem sandigen Lehmboden Um die Persistenz von Paraquat-Dichtorid im Boden zu erfassen, wurde 1967 ein Langzeit-Feidvcrsuch angelegt. Das Herbizid wurde jährlich, entweder in einer einmaligen Gabe von 4,48 kg/ha, oder in vier getrennten Gaben mit jeweils 1,12 kg/ha angewendet. Von 1969an wurden die Behandlungen geteilt, so dass (a) das Herbizid aufdie Bodenoberfläche und (b) auf die Vegetation apprziert wurde. Von 1970 bis ein-schliesslich 1972 wurden die Parzellen die viermal im Jahr behandelt wurden jeweils kurz nach dem Spritzen gefräst um die Wirkung der Einarbeitung auf die Herbizidpersistenz zu erfassen. Die Untersuchung von Bodenproben die 1971 und 1973 bis zu einer Tiefe von 36 cm gezogen wurden zeigten, dass praktisch die gesamte ausgebrachte Menge an Paraquat noch vorhanden war. Der grösste Teil hefand sich in den obersten 5 cm, aber beträchtliche Mengen drangen bis in die 25–36 cm Bodenschichi ein. In einem zusätzlichcn Labor-versuch wurde Boden vom Versuchsfeld und von zwei weiteren Standorten mit Paraquat versetzt, so dass die Konzentrationen etwa 50, 100 und 150% der 'strong adsorption capacity’ entsprachen. Wenn dann Paraquat mit gesältigtem NH4CI extrahiert wurde, dann betrug die Abnahme nach 17 Woehen zwischen 10 und 35%, was darauf hinweist, dass die Mikroflora der Böden Paraquat nur langsam. wenn uberhaupt abzubauen vermochte. Die Ergebnisse lassen den Schluss zu, dass Paraquat unter Freilandhedingungen im Boden nur langsam oder gar nicht abgebaut wird.

Notes: Summary. The effect of the method of incorporation of prometon into the soil on its phytotoxicity to white mustard was studied in pot experiments. Two groups of method were compared. In the first, the total quantity of soil to be used was mixed with the volume of appropriate prometon solution necessary to produce the required final herbicide and water concentrations. In the second group, the herbicide was initially mixed with a sub-sample of soil which was then diluted with untreated soil to give the required final concentration.Phytotoxicity was greatest when procedures of the second type were followed. There was no difference between the behaviour of wettable powder and unformulated applications. Influence de la méthode d'application de la prométone dans le sol sur sa toxicité pour la moutarde blanche (Sinapis alba L.)

Notes: Fruit harvested from gooseberry plots treated with up to 33·6 kg/ha of chlorthiamid and dichlobenil (applied at two dates) was examined for the presence of residues of 2,6-dichlorobenzonitrile together with the possible metabolites, 2,6-dichlorobenzamide and 2,6-dichlorobenzoic acid. In addition the canned fruit was examined for taint. Residues of 2,6-dichlorobenzonitrile resulting from the application of both herbicides at all rates were below 0·05 ppm. Residues of 2,6-dichlorobenzamide ranged from 0·13 to 0·45 ppm with the greatest residues occurring in fruit from plots treated with the highest amounts of chlorthiamid in March. Fruit from some of the March applications of both herbicides contained residues of up to 0·16 ppm 2,6-dichlorobenzoic acid. No taints were found in the canned fruit.

Notes: Summary. Measurements were made of the time taken for equilibrium to be established during adsorption and desorption under aqueous slurry conditions using monuron, linuron, atrazine and chlorpropham with a variety of adsorbents. An appreciable time was taken for equilibria to be established in adsorption processes, although with one exception, this period was 24 hr or less. Desorption processes were generally rather slower and in seven cases out of eighteen equilibrium was apparently not established in 72 hr. However, in all but two cases it seemed likely that the sorption process was reversible or nearly so.Possible explanations for differences of equilibrium times are discussed together with implications the results might have on the interpretation of leaching phenomena.Vitesse à laquelle est atteint I'équilibre d'adsorption et de désorption dans certains systèmes impliquant des herbicides

Notes: Summary. The absorption of urea and a number of its derivatives by different soils was investigated using a slurry-type procedure. The materials could be listed in the following order of increasing tendancy to be adsorbed: urea, fenuron, methylurea, phenylurea, monuron, monolinuron, diuron. linuron, neburon and chloroxuron. Both N-aryl and N-alkyl substituents appeared to play a part in adsorption. Increasing chain length in the alkyl substituents and chloro- and chlorophenoxy substitution in the aryl substituent increased adsorption. There was no relationship between adsorption and water solubility.Organic matter content was the only soil property that could be related to adsorptive capacity. The evidence of Langmuir isothermal equilibrium plots suggests that only a fraction of the total soil surface is available for the adsorption of substituted ureas.L'adsorption Je l'uré de ses dérivés sur dfférents sols

Notes: Experiments were done to observe the pattern of early root development of radish (Raphanus raphatnistrum L.) and perennial ryegrass (Lolium perenne L.), the mobility of chlortoluron following application to the soil surface, the effect of protecting the subterranean shoots of four plant species on their response to chlortoluron and terbutryne and the relative quantities of 14C-labelled chlortoluron taken up by radish and Avenu fatua from root and shoot zone exposure. Both chlortoluron and terbutryne appear to be able to enter the plants examined, Alopecurus myosuroides, Stellaria media, perennial ryegrass and radish, through roots and shoots. It is suggested that shoot uptake is relatively more important for plants like perennial ryegrass than for those whose roots develop more quickly and invade the soil above the seed, such as radish. The quantities of radioactive chlortoluron taken up from soil containing 400 ng g−1 showed that less than 3 ng per plant could reduce A. fatua fresh weight by 17–40% while over 30 ng per plans had little effect on radish. By comparison 2 kg ha−1 chlortoluron applied to the soil surface of pots which were sub-irrigated for 3 weeks gave a concentration of 170 ng g−1 in the layer of soil 10–12 mm from the surface. It is suggested that for shallow germinating species with herbicides of physical and phytotoxic properties similar to chlortoluron, the solvent action of rainfall, together with diffusion, is enough to allow the transport of toxic quantities to the target plant although any leaching action is likely to increase activity.

Notes: 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