Interactions between pre- and post-emergence weed harrowing in spring cereals

Pre- and post-emergence weed harrowing were studied in spring cereals in different environments and with two types of harrows in Norway during 2004–2006. The objectives were to investigate interactions between pre and post-emergence weed harrowing and the importance of harrow type. We hypothesised that pre- and post-emergence harrowing interact positively, that a combination gives more stable weed control effects than pre- and post-emergence weed harrowing used alone, and that a harrow type with bent tines is more aggressive and suitable on hard-packed soils than a harrow with strait tines. The results only supported the last of these hypotheses. Post-emergence weed harrowing controlled a certain percentage of the present weeds, and this percentage was not dependent on pre-emergence weed harrowing. On average, pre-emergence harrowing reduced weed density by 26% and weed biomass by 22%, while the average effect of postemergence harrowing was 47% on weed density and 41% on weed biomass. The combined effect of pre- and post-emergence weed harrowing was 61% on weed density and 54% on weed biomass. The combination did not give more stable weed control effects than preand post-emergence weed harrowing used alone. Preemergence harrowing increased the average crop yield by 6.2%, post-emergence harrowing by 4.0% and the combined effect was 10%. Crop yield was mainly increased on hard-packed soils. Weed and crop responses varied strongly among experiments, but the efficacy of pre- and post-emergence weed harrowing was positively correlated across experiments. Weed species composition was of minor importance regarding weed control. The study indicates that one aggressive postemergence cultivation may be as good as one preemergence and one less aggressive post-emergence cultivation. However, little is known about the interactions between cultivation at different crop and weed growth stage

Control of perennial weeds based on weed biology and environmental considerations

Timing, type and duration of tillage operations and cropping practices are of importance for reducing the regeneration of perennial weeds and also for minimizing the environmental impacts of such operations. In the present work and with reference to previous publications we find that, based on the knowledge gained on growth patterns, sensitivity to competition, growth potential of roots and mechanical and management measures it is possible to coordinate control of perennial weeds with considerations of yield and reduced environmental impact

The discovery of the Younger Dryas, and comments on the current meaning and usage of the term

The Younger Dryas (YD) cold event was discovered in Denmark by Hartz and Mithers in 1904 and the term coined by Hartz in 1912. It was identified as a lacustrine clay bed containing plant macrofossils of an Arctic flora, including Dryas octopetala, and lying between Allerød and Holocene gyttjas containing a warmer flora with birch trees. The YD is unique in the sense that it is the largest and most abrupt climate change on Earth since the Last Glacial Maximum and thus within the reach of radiocarbon dating. Yet, I consider it is part of a regular Dansgaard-Oeschger event. The term has been used for a climate event and for lithostratigraphical, biostratigraphical and several other stratigraphical units. I prefer using it as a geochronological and chronostratigraphical unit, i.e. that the YD represents a specific period of geological time and the rocks and sediments formed during this period. In the type area of southern Scandinavia, the YD chron represents the age and duration of the cold event.publishedVersio

Triassic palynoevents in the circum-Arctic region

Triassic successions of the present-day Arctic contain abundant and diverse assemblages of nonmarine palynomorphs that have provided important biostratigraphic information. Dinoflagellate cyst are biostratigraphically useful in marine intervals in the Upper Triassic. Based on published records, we present a compilation of 78 last occurrences (LOs), first occurrences (FOs), and some abundance events that are anticipated to have correlation potential in the Arctic region. Palynological work has been carried out in many Arctic areas, with extensive palynological research published on the Triassic successions of the Norwegian Barents Sea and Svalbard. An updated, recent palynological zonation scheme exists for that region, integrating previous schemes and illustrating the chronostratigraphic value of palynology in the Triassic. For the Lower and Middle Triassic, good ammonoid control ties the palynological zones to the chronostratigraphic scale. Independent control is sparse, and resolution is lower in the Upper Triassic, so that palynology is commonly the only biostratigraphic discipline available for chronostratigraphic dating and correlation

Ugrasharving i korn

Denne undersøkelsen har som målsetning å finne klarere kriterier om det skal harves, når det skal harves, hvordan harva skal stilles inn og hvilke harvtyper og tindetyper som er optimale på forskjellige jordtyper. Videre skal en se på hvordan underkultur kan tilpasses ugrasharving. Resultatene første år er interessante, men det er for tidlig å trekke konklusjoner

Permian palynoevents in the circum-Arctic region

Permian palynofloras are recorded around the present-day Arctic and are typically dominated by taeniate and non-taeniate pollen, with intervals of spore domination. The assemblages show close similarities around the Arctic. Based on the published record, we present a compilation of 23 last occurrences (LOs), first occurrences (FOs), and some abundance events. These are anticipated to have regional correlation potential. In general, the Permian palynofloras of the Arctic have not been extensively studied, and the resolution is low due to a general lack of independent age control

Introduction to the “Circum-Arctic Palynological Event Stratigraphy” (CAPE) series of papers

Palynomorphs are one of the few groups of fossils that provide biostratigraphic control in marine to nonmarine rocks and can be applied as proxies for paleoenvironmental and paleoclimatic interpretations. Their utility is enhanced by their microscopic size, which is usually less than 200 micrometres; they are thus easily recovered from small rock samples. They occur throughout the Phanerozoic and are therefore invaluable in refining biostratigraphic control of Arctic successions in Alaska, Arctic Canada, Greenland, northern Europe, and northern Russia. The objective of the Circum-Arctic Palynological Event (CAPE) Stratigraphy series of papers is to integrate data published on Arctic palynomorphs to delineate palynological events (palynoevents) across the Arctic for the Silurian to Cenozoic. Once the series of papers is complete, the data will also be used to compile a TimeScale Creator datapack that can be updated and calibrated on an ongoing basis. Palynoevents include taxon originations (first occurrences or FOs) and extinctions (last occurrences, or LOs) and some abundance events. The palynoevents are correlated with established chronostratigraphic horizons such as bases of ammonoid zones or stages, and hence their chronostratigraphy is independent of the absolute time scale in millions of years. In addition to the palynostratigraphic papers, the series includes a paper detailing the paleogeography of the circum-Arctic regions, including informative maps, as well as a paper providing a palynological perspective of the Cenozoic shift from greenhouse to icehouse conditions

Ice-free conditions in Novaya Zemlya 35,000 to 30,000 cal years BP, as indicated by radiocarbon ages and amino acid racemization evidence from marine molluscs

Novaya Zemlya was covered by the eastern part of the Barents-Kara ice sheet during the glacial maximum of marine isotope stage 2 (MIS 2). We obtained (14)C ages on 37 samples of mollusc shells from various sites on the islands. Most samples yielded ages in the range of 48-26 (14)C Ky. Such old samples are sensitive to contamination by young (14)C, and therefore their reliability was assessed using replicate analyses and amino acid geochronology. The extent of aspartic acid racemization (Asp D/L) indicates that many of the (14)C ages are correct, whereas some are minimum ages only. The results indicate that a substantial part of Novaya Zemlya was ice-free about 35-27 (14)C Kya, and probably even earlier. Corresponding shorelines up to > 140 m a.s.l. indicate a large Barents-Kara ice sheet during early MIS 3. These results are consistent with findings from Svalbard and northern Russia: in both places a large MIS 4/3 Barents-Kara ice sheet is postulated to have retreated about 50 Kya, followed by an ice-free interstadial that lasted until up to ca. 25 Kya. The duration of the MIS 2 glaciation in Novaya Zemlya was calculated by applying the D/L values to a kinetic equation for Asp racemization. This indicates that the islands were ice covered for less than 3000 years if the basal temperature was 0(o)C, and for less than 10 000 years if it was -5 degrees C

Cut fallow to replace black fallow in an organic production system

Couch grass (Elymus repens) has large impact on yield and management strategies in temperate areas of the world. The control is to a large extent based on repeated soil cultivations in organic farming. Our aim was to investigate methods to improve the competitive effect of white clover by management. The hypothesis was that cutting (fragmentation) of the rhizomes by making slits in the soil by a spade (spading) would increase the number of couch grass shoots, thus improve the effect of repeated mowing. We conclude that Cross cutting to 10 cm could reduce the amount of rhizomes, but that the effect is variable. We also conclude that the cross cutting do not improve the effect of mowing. Cross cutting reduce the amounts of couch grass shoots

Veien til bedre pløying : - en veiledning

All jordarbeiding skal ha som formål å bedre vekstforholda for kulturplantene. Rett utført jordarbeiding er enormt viktig for å få optimal effekt mot rotugras. Pløying legger grunnlag for såbedet og er i seg sjøl et ugrastiltak, vel å merke når plogen har riktig utstyr og er riktig innstilt. Riktig pløying, slik at det er fullstendig gjennomskjæring, at alle velter er like brede og høge, osv er viktig for at alle etterfølgende arbeidsoperasjoner som slodding, harving, såing og senere ugrasharving og radrensing, skal bli optimal. Pløyinga må utføres når jorda er lagelig for å redusere faren for jordpakking. Det er viktig å velge mellom høst eller vårpløying ut i fra faren for erosjon. Dette heftet bør kunne benyttes av alle fordi utstyr, vedlikehold og innstilling i hovedsak er det samme om en har stor eller liten plog. Den faglige bakgrunn for dette heftet baserer seg på forskning vedrørende pløying, men også i stor grad på forfatterens erfaring gjennom mange år. Forfatteren har undervist studenter ved Høgskolen i Hedmark gjennom tretti år, vært trener og dommer i tevlingspløying, og ikke minst holdt utallelige kurser for bønder og andre innen jordbruk. Kursene for praktiske bønder har gitt erfaring i hvor det skorter for de som skal få til en agronomisk riktig pløying.Statens landbruksforvaltning (SLF