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.
2006
Forfattere
Marianne BechmannSammendrag
Resultatene fra en undersøkelse av lokale tilførsler av fosfor til vestre Vansjø har klarlagt at disse har større betydning enn tidligere antatt. Som konsekvens av dette har myndighetene økt fokus på gamle og nye tiltak mot avrenning av fosfor fra jordbruket.
Sammendrag
Temporal changes in the scores of selected soil fertility indices were studied over six years in three different cases of organic crop rotation located in southern, eastern and central Norway. The cropping history and the initial scores of fertility indices prior to conversion to organic cropping differed between the sites. Crop yields, regarded as an overall, integrating fertility indicator, were in all rotations highly variable with few consistent temporal trends following the first year after conversion. On the site in eastern Norway, where conversion followed several years of all-arable crop rotations, earthworm number and biomass and soil physical properties improved, whereas the system was apparently degrading with regard to P and K trade balances and contents in soil. On the other two sites, the picture was less clear. On the southern site, which had a relatively fertile soil before conversion, the contents of soil organic matter and K decreased during the six-year period, but the scores of other fertility indices showed no trends. On the site in central Norway, there were positive trends for earthworm-related indices such as worm biomass and tubular biopores, and negative trends for soil porosity. The results, especially those from the eastern site, illustrate the general difficulty in drawing concllusions about overall fertility or sustainability when partial indicators show divergent trends. Consequently, the study gave no unambiguous support to the initial working hypothesis that organic farming increases inherent overall soil fertility, but rather showed that the effect varied among indicators and depended on status of the cases at conversion. It is concluded that indicators are probably better used as tools to learn about and improve system components than as absolute measures of sustainability.
Forfattere
Atle Hauge Hans Olav Eggestad T. Sveistrup Tore SveistrupSammendrag
Det er ikke registrert sammendrag
Sammendrag
Freezing and thawing influence the transport potential and pathways for contaminants by altering the soil physical properties. Firstly, soil frost delays or impedes infiltration of rain and meltwater, reducing the transport rate of dissolved contaminants. But at the same time, particle bound contaminants may be mobilised because the reduced infiltration capacity increases surface runoff and erosion risk. Secondly, freezing water expands and imposes mechanical stresses on the soil, which may cause aggregate breakdown and facilitate particle detachment and transport. The influence of repeated freezing and thawing on aggregate stability of different soils is poorly documented for Nordic winter conditions. The purpose of this study (Kværnø and Øygarden, subm.) was to quantify the effect of variable freeze-thaw cycles and soil moisture conditions on aggregate stability of three soils: Silt, structured clay loam (Clay A) and artificially levelled silty clay loam (Clay B). These soils are representative of two erosion prone areas in South-eastern Norway. Field moist surface soil was sieved into the fraction 1- 4 mm, and packed into cylinders. The water content of the soil was adjusted, corresponding to matric potentials of -0.75, -2 and -10 kPa. The soil cores were insulated and covered, and subjected to 0, 1, 3 or 6 freeze-thaw cycles: freezing at "15"C for 24 hours, and thawing at 9"C for 48 hours. Aggregate stability was measured in a rainfall simulator (representing rainfall) and a wet-sieving apparatus (representing surface runoff). The aggregate stability of Silt was found to be significantly lower than of Clay A and Clay B. Clay A and Clay B had similar aggregate stabilities, even if it was expected that the artificially levelled Clay B would have lower stability. Freezing and thawing decreased the aggregate stability for all three soils, but the effect was more severe on the silt soil. There was no evident effect of water content on the aggregate stability, probably due to experimental limitations. The wet-sieving apparatus resulted in less aggregate breakdown than the rainfall simulator. Rainfall impact seemed to be more detrimental than wet-sieving the more unstable the soil was, that is, after many freeze-thaw cycles, and on silt soil. The results indicate that freezing and thawing is an important factor influencing the erosion risk of the studied soils. In the future, climate change is expected to give more unstable winters with more freezing and thawing events. Combined with more precipitation as rainfall during the winter period both runoff and erosion will probably increase, possibly resulting in heavier loads of particulate bound contaminants to surface waters. The results are also helpful for improving predictions of contaminant fate and transport, as most of the existing hydrological and soil erosion prediction models do not satisfactorily describe soil processes occurring under Nordic winter conditions. This study focused on arable soils with conventional agricultural management, where plant nutrients and pesticides pose a threat to water quality. It would be useful to conduct similar experiments on soils where other organic and inorganic contaminants are of concern, e.g. on soils where sewage sludge and compost have been applied, and soils in road cuttings and on contruction sites. References Kværnø, S.H. & Øygarden, L. submitted: The influence of freeze-thaw cycles and soil moisture on aggregate stability of three soils in Norway.
Sammendrag
Grønnsakdyrking foregår ofte på intensivt dyrkede arealer med tilførsel av store mengder næringsstoffer, noe som gjerne fører til store overskudd i næringsbalansen. Tap av næringsstoffer fra slike arealer er som regel større enn fra øvrige jordbruksarealer. Risiko for avrenning av fosfor er særlig stor på grunn av generell sterk fosforgjødsling og ved at slike åkerkulturer er mer utsatt for jorderosjon, særlig etter høsting i forbindelse med sterke nedbørsepisoder.
Forfattere
Hallvard Jensen Per-Arne Amundsen J. Malcolm Elliott Thomas Bøhn Paul Eric Aspholm Paul Eric AspholmSammendrag
Prey consumption rates of piscivorous brown trout, Salmo trutta, were studied in the Pasvik watercourse, which forms the border between Norway and Russia. Estimates of food consumption in the field were similar to or slightly less than maximum values from a bioenergetic model. The piscivore diet consisted mainly of vendace, Coregonus albula, with a smaller number of whitefish, C. lavaretus. Individual brown trout had an estimated mean daily intake of approximately 1·5 vendace and 0·4 whitefish, and a rapid annual growth increment of 7-8 cm year-1. The total population of brown trout >25 cm was estimated as 8445 individuals (0·6 individuals ha-1), giving an annual consumption of 1553880 (±405360 S.E.) vendace and 439140 (±287130 S.E.) whitefish for the whole watercourse. The rapid growth in summer of brown trout >25 cm indicated a high prey consumption rate.
Sammendrag
Vannprøvetaking ved overvåkning av avrenning fra landbruksarealer har vært gjort ulikt i de Nordisk land. Behovet for å se på hvor store forskjeller i estimering av næringsstofftransport som de ulike prøvetakingsstrategiene gir, var bakgrunnen for dette prosjektet. I tre bekker i Sør-Norg ble det foretatt sammenlignende studier av tre prøvetakingsopplegg: ukentlige vannføringsproporsjonale blandprøver, ukentlige tidsproporsjonale blandprøver og stikkprøver. De ulike prøvetakingsstrategiene ga mer like utslag for nitrogen enn for fosfor og suspendert materiale. Stikkprøver fanget i mindre grad opp høye konsentrasjoner av fosfor og suspendert materiale i flomsituasjoner enn blandprøvemetodene, og ga følgelig underestimering av stofftapet. Blandprøver uttatt proporsjonalt i forhold til vannføringen ga mest pålitelige resultater både i perioder med høy og med liten vannføring. Vannføringsproporsjonal prøvetaking ble derfor anbefalt for videre studier av vannkvalitet i landbruksområder.
Forfattere
Dan Aamlid Kjell Andreassen Gro Hylen Nicholas Clarke Volkmar Timmermann Ingvald Røsberg Halvor Solheim Wenche AasSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Marianne BechmannSammendrag
Risiko for fosforavrenning og vannforurensing er større fra grønnsaksarealer enn fra andre jordbruksarealer. Grønnsaksarealer har ofte høye fosforkonsentrasjoner i jorda på grunn av høy fosforgjødsling. Dessuten bidrar kraftig jordarbeiding i forbindelse med høsting av grønnsaker til å øke erosjonsrisikoen. Målinger viser at fosfortapene fra disse arealer er store.