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
Lars Tørres HavstadSammendrag
For å få tørka frøet helt ned til lagerfast vare på 12 prosent er det viktig å vite sammenhengen mellom frøets vanninnhold og den relative luftfuktigheten i tørkelufta Det er imidlertid gjort få undersøkelser som viser hvordan frøets vanninnhold hos ulike grasarter varierer med luftfuktigheten. For å se nærmere på denne sammenhengen pågår det for tida forsøk på Bioforsk Landvik hvor frø av fem ulike arter (timotei, engsvingel, bladfaks, strandrør og rødsvingel) blir plassert i lufttette glassbeholdere med kjent relativ luftfuktighet. De foreløpige resultatene fra forsøket viste at når den relative luftfuktigheten i lufta holdt seg mellom 10 og 45 prosent var likevektskurven mellom frøets vanninnhold og luftas relative luftfuktighet ganske lik i de ulike artene. Når luftfuktigheten økte ytterligere steg imidlertid vanninnholdet mer i de storfrøa artene (eks. bladfaks) enn i artene med små frø (eks. timotei). For å få tørket frøet ned til lagerfast vare på 12 prosent måtte luftas relative luftfuktighet ned i 50 prosent i bladfaks, mens 55 prosent klarte seg i timotei.
Forfattere
Lars Tørres Havstad Trygve S. AamlidSammendrag
Innmeldt kontraktareal av konvensjonelt og økologisk dyrka frø i 2006 var totalt 30803 daa. Dette er 9 % lavere enn tilsvarende areal i 2005, men 20 % høyere enn i 2004. Nedgangen i kontraktareal fra 2005 til 2006 skyldtes særlig mindre konvensjonelle utlegg av Vega og Grindstad timotei og Norild engsvingel. Timotei la i 2006 beslag på 53 prosent av det totale arealet, etterfulgt av engsvingel (22%), rødkløver (15%) og engrapp (3%). Av timoteiarealet utgjorde de tre sortene Grindstad, Vega og Noreng henholdsvis 69, 23 og 8%, mens Norild, Fure, Stella og Salten ble frøavlet på henholdsvis 53, 40, 6, og 1% av det totale engsvingelarealet i 2006. Av rødkløver ble det dyrket mest frø av Bjursele (36%), Lea (25%) og Nordi (22%). Det ble i 2006 høsta 57 frøavlsforsøk, noe som er likt med året før. Forsøkene ble utført på Bioforsk Øst Landvik (17 felt) og i regi av Vestfold forsøksring (11 felt), Buskerud forsøksring (6 felt), Hedmark forsøksring (5 felt), Telemark forsøksring (5 felt), Forsøksringen SørØst (5 felt), Aust-Agder forsøksring (3 felt), Forsøksringen FABIO (2 felt), Trøndelag forsøksring (2 felt) og Romerike forsøksring (1 felt).
Forfattere
Lars Tørres HavstadSammendrag
Med utgangspunkt i de meterologiske målingene på værstasjonene Landvik (Aust-Agder) og Lyngdal (Vest-Agder) gir artikkelen en oversikt over været på Agder i vekstsesongen 2006.
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.
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.
Sammendrag
Data from experiments in carrots with cavity spot and post harvest diseases and use of PCR-based detection were presented.
Forfattere
Lars NesheimSammendrag
Resultat frå 17 forsøksfelt med ulike hausteregime for sorter av engrapp og engsvingel er presentert. Engrapp etablerte seg seint, og i første engår produserte engsvingelsortane klart store avling enn engrappsortane. I seinare år var det ingen sikre avlingsskilnader.
Sammendrag
To avoid problems with seed borne diseases in organic cereal production, seed health testing should be compulsory in certification of organic seed. In general, significantly lower infection frequencies of seed borne diseases are recorded on seedlings than on seed. Thresholds for the amount of seed borne inoculum that can be accepted for organic production are therefore needed. The aim of the work presented is to compare transmission rates of Drechslera on barley and oats under organic and conventional conditions, to be able to decide if existing thresholds used to assess the need of chemical seed treatment, can be applied for acceptance of organic seed lots, or for recommendation of alternative treatments. Field experiments were carried out in 2005 in conventional and organic fields situated close to each other at each of three locations (south/east-Norway, east-Norway and mid-Norway). 10 seed lots of barley and 10 lots of oats, with a range of seed infections (barley: 0-94 % Drechslera teres, average 31.4 %; oats: 0-66 % Drechslera avenae, average 22.0 %) were planted in rows of 100 seeds with 8 replicates in each location/`growing system". Percent emergence and seedlings with primary infections were recorded at BBCH 12-13. On average in the three locations 2.5 % and 1.8 % barley seedlings were infected when grown in conventional and organic fields, respectively. In oats, 2.0 % and 0.9 % infected seedlings were recorded in conventional and organic fields, respectively. Similar experiments will be carried out in 2006 and results from this will also be presented.
Sammendrag
available, especially in Norway. The objective of the present research was to estimate C losses from cultivated peatlands in West Norway by three independent methods: 1) long-term monitoring of subsidence rates, 2) changes in ash contents, and 3) soil CO2 flux measurements. Subsidence of cultivated peat soils averaged about 2.5 cm y-1. We estimated that peat loss and compaction were respectively responsible for 38% and 62% of the total subsidence during a 25-year period after drainage. Based on this estimate the corresponding C loss equals 0.80 kg C m-2 yr-1. The observed increase in mineral concentration of the topsoil of cultivated peat is proportional to their C loss, providing no mineral particles other than lime and fertilizers are added to the soil. Using this novel approach across 11 sites, we estimated a mean C loss of 0.86 kg C m-2 y-1. Soil CO2 flux measurements, corrected for autotrophic respiration, yielded a C loss estimate from cultivated peat soils of 0.60 kg C m-2 yr-1. The three methods yielded fairly similar estimates of C losses from Norwegian cultivated peatlands. Cultivated peatlands in Norway cover an estimated 63 000 ha. Total annual C losses from peat degradation were estimated to range between 1.8 and 2 million tons CO2 y-1, which equals about 3-4 % of total anthropogenic greenhouse gas emissions from Norway.