ALBERT

Notes: Abstract The transport of anhydrous NH3-solubilized soil organic matter from surface to subsurface soils may affect subsurface microbial activity. In the present study we determined the impact of anhydrous NH3-N fertilizer on organic C solubilization and the propensity of solubilized C to leach with percolating water. In fertilized treatments, anhydrous NH3 was subsurface-banded at 20g N m-2 in ridge or valley areas of a ridge tillage system. In contol treatments, 0g N m-2 was banded into the valley area of a ridge tillage system. Rainfall (17 cm) was applied with a drop-type artificial rainfall simulator 3, 10, and 24 days after the fertilizer application. The treatments were replicated twice. Grid lysimeters (15 by 15 cm) were placed 75 cm below the soil surface of a Brandt silty clay loam (fine-silty over sandy or sandy skeletal mixed Pachic Udic Haploboroll). Lysimeters were used to collect percolating water temporally and spatially. The application of N fertilizer increased dissolved organic C concentrations in percolating water when rainfall was applied 3 days after the fertilizer application. However, when the rainfall was applied 24 days after the fertilizer application the dissolved organic C concentrations in percolating water was not influenced by anhydrous NH3 application. The smaller dissolved organic C concentrations in percolating water with a longer incubation time were most likely the result of microbial assimilation or respiration of solubilized C.

Notes: Summary The application of NH inf4 su+ -based fertilizers to soils slowly lowers soil pH, which in turn decreases nitrification rates. Under these conditions nitrification and N mineralization may be reduced. We therefore investigated the impact of liming fertilizer-acidified soils on nitrification and N mineralization. Soil samples were collected in the spring of 1987 from a field experiment, initiated in 1980, investigating N, tillage, and residue management under continuous corn (Zea mays L.). The pH values (CaCl2) in the surface soil originally ranged from 6.0 to 6.5. After 6 years the N fertilizer and tillage treatments had reduced the soil pH to values that ranged between 3.7 and 6.2. Incubation treatments included two liming rates (unlimed or SMP-determined lime requirement), two 15N-labeled fertilizer rates (0 or 20 g N m-2), and three replicates. Field-moist soil was mixed with lime and packed by original depth into columns. Labeled-15N ammonium sulfate in solution was surface-applied and columns were leached with 1.5 pore volumes of deionized water every 7 days over a 70-day period. Nitrification occurred in all pH treatments, suggesting that a ferilizer-acidified soil must contain a low-pH tolerant nitrifier population. Liming increased soil pH values (CaCl2) from 3.7 to 6.2, and increased by 10% (1.5 g N m-2) the amount of soil-derived NO3 --N that moved through the columns. This increase was the result of enhanced movement of soil-derived NO3 --N through the columns during the first 14 days of incubation. After the initial 14-day period, the limed and unlimed treatments had similar amounts of soil N leaching through the soil columns. Lime increased the nitrification rates and stimulated the early movement of fertilizer-derived NO3 --N through the soil.

Notes: Growth inhibition of pot-grown Elymus repens (L.) Gould by fluazifop-butyl was occasionally enhanced by pre-treatment with ethephon. Studies with 14C-labelled fluazifop-butyl showed that ethephon increased the accumulation of 14C in basal buds and proximal parts of the rhizome system. This potential modification in the distribution of fluazifop-butyl within E. repens rhizomes may have reduced regeneration and recovery of the E. repens, particularly from the basal buds, although there was no increase in the proportion of 14C translocated into the rhizome. Also, ethephon not only activated the sinks in the rhizome but in the foliage of E. repens as well, and could initiate buds without sinks. The effects of ethephon on fluazifop-butyl phototoxicity were irregular in their occurrence and degree, and possible reasons for this are discussed.Effets depré-traitements à I'étéphon sur la réponse de Elymus repens au fluazifop-butylLors d'expériences en pots, des pré-traitements & 1'étéphon augmentaient occasionnellement 1'inhibition de croissance d'Elymus repens (L.) Gould traité au fluazifop-butyl. Des etudes avec du fluazifop-butyl marqué au 14C ont montré que l'éléphon augmentait l'accumulation de 14Cdans les bourgeons de la base et dans les parties proximales des rhizomes. Bien que la proportion de 14C transportée dans le rhizome ne soit pas accrue, cette modification de la distribution du fluazifop-butyl à l'intérieur des rhizomes d'E. repens pourrait limiter la régénération et la reprise de croissance, en particulier à partir des bourgeons de la base. En outre, l'étéphon activait des puits métaboliques non seulement dans le rhizome mais aussi dans le feuillage d'E. repens et pouvait initier des bourgeons qui ne se comportaient pas comme des puits métaboliques.Tant 1'existence que 1'intensité des effets de 1'étéphon sur la phytotoxicité du fluazifop-butyl étaient irréguliers et les raisons possibles en sont discutées. Wirkung einer Vorbehandlung mit Ethephon auf die Reaktion von Elymus repens (L.) Gould auf Fluazifop-butyl In Gewächshausversuchen war die Wuchshem-mung von Elymus repens durch Fluazifop-butyl gelegentlich durch eine Vorbehandlung mil Ethephon verstärkt. Untersuchungen mil 14C-Fluazifop-butyl ergaben, daß Ethephon die Ak-kumulation von 14C in basalen Knospen und proximalen Teilen des Rhizoms förderte. Die so mögliche Veränderung der Verteilung von Fluazifop-butyl in den Quecke-Rhizomen kann zu der reduzierten Regeneration der Pflanzen geführt haben, vor allem aus den basalen Knospen, obwohl insgesamt keine groBere 14C-Menge im Rhizom gefunden wurde. Ethephon aktivierte nicht nur die Sinks im Rhizom, son-dern auch in den oberirdischen Teilen und kon-nte zur Ausbildung von Knospen ohne Sinks führen. Die Wirkungen des Ethephons auf die herbizide Wirkung des Fluazifop-butyls war unregelmaßig, und die moglichen Grunde dafiir werden diskutiert.

Notes: Fluazifop-butyl, haloxyfop and sethoxydim with adjuvant oil were applied for three successive growing seasons to established strawberries infested with Elymus repens. The weed was virtually eradicated by three applications of haloxyfop (0.8 kg a.e. ha−1) in successive years. A similar effect was given by five applications of haloxyfop (0.4 kg a.e. ha−1) and fluazifop-butyl (1.6 kg AI ha−1) in three growing seasons. Lower rates of haloxyfop and fluazifop-butyl, and a high rate of sethoxydim (1.6 kg AI ha−1) applied five times were less effective, the ground cover of E. repens shoots not being reduced by the end of the experiment although weight of living rhizome was only 10-30% of that on untreated plots.Fruit yields on treated plots generally reflected the level of E. repens control, but there was some evidence of crop phytotoxicity from herbicide treatments. During the experiment E. repens untreated plots increased from about 30-100% ground cover and reduced yield 13, 28 and 68% in successive years compared with weed-free plots.

Notes: Three indices were used to assess the tolerance of strawberries to herbicides in different experiments. Tolerance was compared using a tolerance index. TI. (= ED value of the lest herbicide/ ED value of a standard herbicide). The degree of response to increases in dose was compared by calculating a dose-response index, RI (= ED50/ED20 value) for each herbicide and the speed of action by a speed of action index. SI (=time to minimum ED value, test herbicide'time to minimum ED value, standard herbicide).The optimum time of the final assessment varied according to the mode of action of the herbicides being tested. There was generally good agreement between ED values obtained from scores of plant condition and from fresh weight measurements. ED20 values gave more useful estimates of relative tolerance than ED50's where the degree of response to increasing doses was different.

Notes: The tolerance of strawberries to herbicides was tested by applications to the roots of plants growing in sand and by foliage applications to plants grown in compost, and compared with tolerance in the field. Dimefuron was safe as a foliar application but much more toxic than simazine when applied in sand or in the field. Metamitron caused slight injury as a foliar spray; in sand and in the field it was intermediate in toxicity between simazine and lenacil. At normal rates propachlor was safe as a foliar spray and much safer than lenacil when applied in sand. High rates had no adverse effect in the field.Ethofumesate and pendimethalin caused some temporary stunting when applied to foliage, but were less toxic than lenacil when applied to roots in sand. Field applications of both herbicides at 1–1.5 kg/ha were safe. Foliage sprays of bentazone, oxadiazon and oxyfluorfen severely damaged the sprayed leaves, but these herbicides were less active than lenacil when applied to the roots. In the field they caused severe leaf damage, but by the end of the growing season the plants had recovered.The experiments demonstrated the value of separate root and shoot activity tests for indicating which herbicides merit further field testing.

Notes: Sand-culture techniques for determining the tolerance of fruit crops to herbicides applied to the roots were investigated. Of the methods examined, a single application to pots with a closed drainage system was the most useful provided they were protected from rain. A semi-automatic system for applying herbicides was developed for use where repeated treatment was required. Visual scoring of plant condition was the most informative method of assessing response and was reliable. Results correlated well with weight measurements of leaves, shoots or whole plants. For each herbicide ED50 values were derived from dose-response curves and used to express relative tolerance. The slopes of these curves provided an indication of the rate of change of response with dose. The relative tolerance of a range of fruit crops to simazine corresponded to known relative tolerance in field conditions in the U.K.It is concluded that sand-culture techniques can be used as a preliminary screen to find new soil-acting herbicides for perennial crops and to detect differences in tolerance between cultivars. They also enable the direct influence of plant and seasonal factors on response to root-applied herbicides to be studied. Large numbers of treatments can be tested in a small area with the certainty of obtaining positive results. Evaluation des techniques de culture sur sable pour l'étude de la résistance des cultures fruitières aux herbicides agissant par le sol Les auteurs ont étudiè les techniques de culture sur sable pour déterminer la résistance des cultures fruitiéres aux herbicides racinaires, Parmi les méthiodes examinées, celle comportant une seule application, avec un systéme clos de drainage, s'est révélée la plus pratique, à condition qu'elle comporte une protection contre la pluie. Un systéme semi-automatique pour l'application des herbicides a été mis au point pour les cas où des traitements répétés sont nécessaires. L'observation visuelle du comportement de la plante s'est montreée la méthode la plus instructive pour apprécier les réactions; c'est aussi une méthode súre. Les résultats ont montré une bonne concordance avec les mesures pondérales des feuilles, des pousses, ou des plantes entiéres. Pour chaque herbicide, les valeurs de la E.D. 50 ont étć déduites des courbes de réaction en fonction de la dose et utilisées pour exprimer la résistance relative. La pente de ces courbes a fourni une indication sur le taux de modification de la réaction en fonction de la dose. La résistance relative d'une série de cultures fruitiéres ȧ la simazine a correspondu ȧ la résistance relative constatée au champ dans les conditions du Royaume-Uni.Il en est conclu que les techniques de culture sur sable peuvent être utilisées comme tests de sélection primaire pour découvrir de nouveaux herbicides agissant par le sol pour le désherbage des cultures pérennes, ainsi que pour déceler les différences de résistance entre cultivars. Ces techniques rendent ègalement possible l'étude de l'influence directe de la plante et des facteurs saisonniers sur les réactions aux herbicides racinaires.De nombreux traitments peuvent ètre étudiés sur une surface réduite avec la certitude d'obtenir des résultats positifs. Beurteilung von Sandkulture-Techniken für die Untersuchung von Obstgewächsen aufihre Toleranz gegenüber Bodenherbiziden Es wurden Sandkultur-Techniken zur Bestimmung der Toleranz von Obstgewächsen gegenüber bodenapplizierten Herbiziden geprüft. Von den geprüften Methoden war die einmalige Herbizidgabe zu Gefässen mit einem geschlossenen Drainage-system das brauchbarste Verfahren, unter der Voraussetzung. daß die Gefässe vor Regen geschützt waren. Für die Fälle, in denen eine mehrmalige Herbizidapplikation zu erfolgen hat, wurde ein halbautomatisches System entwickelt. Das informativste und zuverlässigste Auswertungsverfahren war die visuelle Bonitur. Die Ergebnisse waren mit Messungen des Gewichts, der Blätter, Sprosse oder der ganzen Pflanzen gut korreliert. Für jedes Herbizid wurden mit Hilfe von Dosis-Wirkungskurven ED50-Werte ermittelt und als Maß der relativen Toleranz benutzt. Die Steigung der Dosis-Wirkungskurven ermöglichten es. die Abhängigkeit von Aufwandmenge und Reaktion zu erfassen. Bei einer Reihe von Obstgewächsen entsprach die relative Toleranz den Werten. die in Großbritannien unter Feld-bedingungen ermittelt wurden.Die Ergebnisse lassen den Schluss zu, dass Sandkultur-Techniken als erster Schritt bei der Suche nach neuen Bodenherbiziden in mehrjährigen Kulturen verwendet werden können, womit auch Toleranzunterschiede zwischen Sorten erfasst werden können. Derartige Verfahren ermöglichen es auch, den Einfluss von Pflanzen und Klimafaktoren auf die herbizidwirkung zu studieren. Mit diesen Techniken können auf kleiner Fläche brauchbare Ergebnisse erzielt werden.

Notes: Summary. The residues remaining in the soil from repeated annual application of simazine at 2–8, 5–6, and 22–4 kg/ha to uncropped plots on a loam soil were measured by chemical or bioassay methods at various intervals after treatment.The total simazine residue present 12 months after the last of three treatments with 2–8 kg/ha and 8 months after the last of five treatments with 5–6 kg/ha was less than 10% of the annual dose. This rapid decomposition is considered consistent with the soil and climatic conditions. In contrast a much larger residue (a mean value of 1·7 kg/ha) was found on plots sampled 21/2 years after the last of two annual applications of simazine at 22·4 kg/ha and the reduction in the amount of residue during the next 12 months was only of the order of 25%.In all treatments the highest concentration of simazine was found in the surface layers of the soil but measurable residues were detected to 60 cm depth, 31/2 years after the last 22·4 kg/ha application.There was considerable variation in the total residues recovered between replicate plots and between different positions on the same plots in all treatments regardless of the depth of the sample. The possible causes of this variation are discussed.Persistance et pénétration de fortes doses de simazine dans un sol non cultivé

Notes: To determine the genetic relationship of anadromous and resident life-history types within and among drainages, and compare several hatchery strains to their progenitor populations, brook charr Salvelinus fontinalis were examined for allozyme and mitochondrial DNA variation. Greater genetic similarity of sympatric anadromous and resident charr was found compared to similar life-history forms allopatrically, suggesting the two life-history types are not reproductively isolated. Low divergence among the mtDNA haplotypes suggests that the two life-history types are members of the same evolutionary lineage. Population differentiation from mtDNA data exceeded that from estimates based on allozymes. Genetic deviations from expectations suggest that the hatchery strains were derived from few individuals.