Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2007
Forfattere
Kjell Mangerud Lars Olav BrandsæterSammendrag
Our objective in an ongoing study is to improving weed harrowing in organic cereal production as well as implementing weed harrowing as an alternative for herbicides in conventional farming. The study includes experiments on three locations during three years. The experiments have included different types of spring tine weed harrows used with different aggressiveness (by differing tine working depths and speeds), cereal developmental stages, soil types (locations) and conditions as well as competition levels (natural variation in severity of weed infestation during three years on three locations). Cereal yield and quality, number and dry matter weight (biomass) of weed and soil water content, soil share strength and soil penetration resistance are recorded. Pre-emergence harrowing, or harrowing at early 1-leaf stage reduced in general weed number and biomass compared to untreated control. The mean weed reduction over locations and years was about 40%, but this reduction was not always significant different to control plots. In general pre-emergence harrowing or at early 1-leaf stage increased the yield compared to untreated, but harrowing at that stage has also under certain circumstances given small yield reductions as well. The combination of pre-emergence harrowing and harrowing at 3-4 leaf stage gave a significant reduction of weed number and biomass compared to untreated control. In general, harrowing twice gave increased cereal yield, but the differences were only significant at one of the locations. The potential benefit of a second harrowing at the 3-4 leaf stage depends on the weed situation, number and biomass, as well as the compatibility of the cereal. Furthermore, our results indicate that the different types of harrows and tines will not do a proper job on all soil types. On light soils all of them have given satisfying results. A normal tine (7 mm bent Einböck or a 10 mm long straight CMN) is not rigid enough on soil types that build a crust after rain. An 8 mm bend Einböck tine, however, broke down the crust and gave increased cereal emergence on such soils. On the other hand it is important not to adjust this tine to aggressive when there is no crust. Other trial show that in stony soils a straight tine will pick up less stones compared with a bent one, stones witch can damage the combine harvester. Our result from one of the location (medium light soil with stones) indicate no difference in yield, reductions in weed number or biomass pr m² with a straight tine compared width a bent one.
Forfattere
Maria Herrero Brita ToppeSammendrag
Pythium aphanidermatum er hos oss best kjent som årsak til aggresiv rothalsråte i veksthusagurk. For første gang er patogenet nå også påvist i forbindelse med rotråte i norske julestjerner
Forfattere
Thomas Holm CarlsenSammendrag
Det er ikke registrert sammendrag
Sammendrag
Cover crops are included in cropping systems to achieve various ecological benefits. In stockless organic cereal systems, nitrogen is commonly supplied by undersowing a legume shortly after sowing of cereals. Retarded growth of annual weeds is considered as an additional benefit of using cover crops. There is, however, less knowledge on the influence of undersown cover crops on the growth of perennial weeds. This issue was addressed in a field experiment at Ås in southeast Norway. For obtaining an experimental field with uniform distribution of the perennial weed species, root fragments of Cirsium arvense and Sonchus arvensis and rhizomes of Elymus repens, were transplanted by hand in the spring of 2001. A split plot design with 3 replications was initiated in 2002 and continued until the autumn of 2006. Barley undersown with red clover versus barley alone composed the two main plot treatments, except in 2006, in which barley was grown without red clover in the whole field. This was combined with four sub-plot mechanical treatments in the autumn: 1) untreated control; 2) mowing; 3) rotary tilling and 4) shallow ploughing plus harrowing. The autumn treatments were only carried out in 2004 and 2005. Number of weeds was counted at different dates throughout the growing season, and weed biomass was assessed just before harvest. Preliminary results indicate that red clover undersown in barley, compared to barley alone, reduced the biomass of established stands of S. arvensis by 50%, 42% and 13% in 2004, 2005 and 2006 respectively. The effect on E. repens varied from +10% in 2004 to -42% in 2005 and -50% in 2006. There was no suppression on established stands of C. arvense (+10%, 0 % and +70%). Of the autumn mechanical treatments rotary tilling and shallow ploughing most effectively retarded the growth of perennial weeds, especially C. arvense and E. repens. Rotary tilling and shallow ploughing reduced mean weed biomass for 2005 and 2006 of C. arvense by 80% (rotary tilling) and 40% (shallow ploughing), and E. repens by 77% and 89%, respectively. Mowing and shallow ploughing reduced mean weed biomass for 2005 and 2006 of S. arvensis most effectively, with a reduction of 62% for both treatments. Although the results need more attention before detailed recommendations can be given, the study indicates clearly that the effect of different mechanical treatments in the autumn depend on weed species.
Forfattere
Paul Hatcher Lars Olav Brandsæter G. Davies A. Luscher H. Hinz R. Eschen U. SchaffnerSammendrag
Docks (especially Rumex obtusifolius and R. longifolius in northern Europe) are important perennial weeds of grassland throughout Europe. In this paper we compare and contrast problems of dock infestation in the UK, Norway and Switzerland, the management techniques currently used, and research into dock control. In the UK, research into farmer"s perceptions of dock problems and control indicates that whilst docks can be a problem, farmers usually target docks in parts of the farm system where they are vulnerable and it is practical and cheap to do so. It is clear that a range of approaches will work best over a period of time. Docks are generally managed through the whole rotation by preventing them from seeding and reducing the vigor of or killing the tap root. In grasslands, a competitive grass sward is sown, a silage rather than hay cut taken, poaching is avoided and docks are usually cut or grazed (e.g. with sheep). Manual removal at targeted stages of rotation is also a proven method, but labour intensive. Topping specific patches with mowers or strimmers is a common mechanical method. Research into Rumex biocontrol has concentrated on the use of the chrysomelid beetle Gastrophysa viridula and the rust fungus Uromyces rumicis. Neither will control docks on their own although the combined agents can produce an additive effect. Several farmers have expressed an interest in using G. viridula, and some have reared the beetle or translocated it. In combination with quick reseeding with Lolium perenne, the beetle can give effective control of young R. obtusifolius seedlings. In Norway, docks are a challenge in all grassland cropping systems and are perceived as a true bottleneck in the development of grassland-based organic production. R. longifolius is more common than R. crispus and R. obtusifolius in Norway, and has been little studied. With the exception of herbicide testing there has been little recent research on docks in Norway, but in one study the biology and ecology of all three species was compared, showing differences in root biomass production and development during stem elongation as well as basic information about root ecology and regeneration. In a recently initiated project, important factors that influence the severity of dock infestation, studies on the weak points in dock growth, and evaluation of biological control of docks and a synthesis of various measures to control these weeds were included. The return on the project has been stressed in terms of increased organic production of meat and dairy products in Norway. In Switzerland, organic farming has increased rapidly and this increase is projected to continue. Two recent surveys amongst farmers have identified R. obtusifolius as the most important obstacle to conversion to organic grassland management. Other docks are also considered problematic, such as R. alpinus on disturbed mountain pastures. R. obtusifolius infestations can reduce the feed value of the sward by up to 30%. Numerous physical control methods have been tested but none of them proved to be economically or ecologically feasible. Figures recorded on an experimental farm suggest that an extra 48 hr labour ha-1 is needed to control R. obtusifolius. The amount of time Swiss farmers are prepared to put into management is often very high, some farmers devoting 1000 man-hours yr-1 to dock control alone. However, this level of management is not feasible for all farms; any reduction in the effort necessary to control docks would be an important advance. Biological control is a logical tool here to integrate into a holistic organic management strategy for docks. In conclusion, no completely satisfactory strategy to control docks especially in organic farming systems exists to date. The most promising approach appears to be a combination of different management methods including biological control.
Forfattere
Thomas Holm CarlsenSammendrag
Det er ikke registrert sammendrag
Forfattere
Thomas Holm CarlsenSammendrag
Det er ikke registrert sammendrag
Sammendrag
To stabilize organic cereal production systems it is necessary to control Canadian thistle (Cirsium arvense) and other perennial weed species. The aim of the two presented experiments (I and II) has been to evaluate the effects of mechanical treatment in spring combined with competition from a one season cover crop. In both experiments we used the same mixture of cover crops; phacelia (Phacelia tanacetifolia Benth.), common vetch (Vicia sativa L.), red clover (Trifolium pratense L.) and Italian ryegrass (Lolium multiflorum Lam.). The first experiment (I) was arranged in a complete factorial split-plot design. In this experiment different root burial depths and root lengths of C. arvense simulated different mechanical treatments. Use of cover crop was the single factor that most effectively reduced the gain of biomass of C. arvense. At the final harvest combined treatment of deep root burial (15 cm), short root length (5 cm) and cover crop reduced number of new shoots of C. arvense by 95% and root biomass by 97% compared to shallow burial and no cover crop. At minimum regenerative capacity of C. arvense the number of leaves were 2 to 6 for the treatment with cover crop and 4 to 8 for the treatment without cover crop. In the second experiment (II), which had a complete factorial design, ± ploughing in autumn was combined with different fallow strategies in spring before sowing the cover crop. The disc harrowing during the fallow period was performed either 2x when fallow lasted for 3 weeks, or 4x when fallow lasted for 6 weeks. Additionally, all combinations of ± ploughing in autumn and length of the fallow period were combined with ± ploughing before sowing the cover crop (all together 8 treatments). In two additional subplots shallow ploughing preceded the autumn ploughing treatment (± ploughing). Preliminary results from experiment II confirms in general the conclusions from experiment I. Combining soil tillage and competition from a fast growing cover crop have potential for retarding perennial weeds. The classical approach for controlling couch grass (Elymus repens) was confirmed in this experiment, the longer soil tillage period the better weed control, and the soil tillage period should be proceeded by a deep ploughing. Ploughing in the autumn gave no additional effect on couch grass. Best control of Canadian thistle was obtained when only shallow ploughing was performed in the autumn, followed by a 6 week soil tillage period (3 weeks was not tested here) in spring and early summer and completed by ploughing before sowing the green manure cover crop. In conclusion, the experiments showed that intensive soil tillage combined with competition from a cover crop gave promising results for weed control. Due to the positive effect of moderate tillage operations attention to factors as nutrient supply, soil structure and energy use may still be ensured while a satisfying weed control is obtained.
Forfattere
Kjell Mangerud Lars Olav Brandsæter Kjell WærnhusSammendrag
The objective of the ongoing study is to obtain new knowledge to provide a fundament for improving weed harrowing in organic cereal production as well as optimising weed harrowing as an alternative for herbicides in conventional farming. Results from field experiments on three locations during three years will be presented and discussed. The experiments included the factors: a) different manufactures of spring tine weed harrows, type of tines and used with different aggressiveness (adjusted through tine working depth and speed); b) cereal developmental stages; and c) soil types (locations) and conditions as well as weed infestation levels. The project included new experimental equipment including a specially constructed 1.5 meter wide harrow, which made it possible to treat many small sub-plots. Cereal yield and quality, number and dry matter weight (biomass) of weeds, and soil water content, soil share strength, and soil penetration resistance were recorded. The resulting intensity of the harrowing operation was measured using digital pictures taken before and after harrowing to give an estimate of cereal coverage of the soil. Pre-emergence harrowing and harrowing at early 1-leaf crop stage reduced in general weed number and biomass compared to untreated control. The mean weed reduction over locations and years was about 40%, but this reduction was not always significant different to control plots. In one year, harrowing at those early stages gave an increase in weed number and biomass, presumably because of rainy weather after harrowing. In general, pre-emergence harrowing and harrowing at early 1-leaf stage increased crop yield compared to untreated, but harrowing at such stages occasionally also resulted in small yield reductions. We conclude, however, that this early harrowing should be carried out every year. Weed harrowing once, either at 2 or 3-4 crop leaf stages, also gave decreased weed number and biomass, but no clear influence on cereal yield. Therefore, harrowing at these late stages is an opportunity, if weather conditions do not allow weed harrowing at earlier stages. The combination of pre-emergence harrowing and harrowing at 3-4 leaf stage gave a significant reduction of weed number and biomass compared to untreated control. In general, harrowing twice gave increased crop yields, but the differences were only significant at one of the locations. The potential benefit of a second harrowing at the 3-4 leaf stage depends on the weed situation, number and biomass, as well as crop competitiveness. Our results have indicated that the threshold for weed harrowing may be around 300 annual weeds m-2, but more knowledge is needed for verifying the level of total number and species. If the number of weeds is less, weed harrowing twice gives a significant reduction in weed number, but not an increase in yield compared to only one weed harrowing at an early growth stage. Furthermore, our results indicate that the different types of harrows and tines will not work properly on all soil types. On light soils, all of them gave satisfying results. However, a normal tine (" 7mm bent Einböck or a " 10mm long straight CMN) is not rigid enough on soil types that build a soil crust after rain. An " 8mm bend Einböck tine, however, was better at breaking a soil crust and thereby improve cereal plant emergence on such soils. On the other hand, it is important not to adjust such tines too aggressive when no crust is present. Another trial showed that a straight tine will pick up less stones on stony soils than a bent one will do, stones which might damage the combiner during combining. Our results from one of the locations (medium light soil with stones) showed that yield as well as reductions in weed number or biomass m-2 was not affected by tine type.
Forfattere
Helge SjursenSammendrag
Frøugrasfrøbanken: * "Forteller" noe om driften. * Forhindre frøsetting mest mulig, både i selve grønnsakkulturen og i "saneringskulturen" * Alltid en balansegang mellom ugrasutviklingen og kostnadene ved ugraskontrollen Rotugras: * Rotugrasfrøbank utgjør bare 2-3% av total frøbank * Rotugraset bør bekjempes mest mulig i "saneringskulturen