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
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.
Sammendrag
Korsmos ugrasplansjer" har nå fått egne internettsider. Der finner du utvalgte plansjer, utfyllende tekter og flere bilder av hver art. På sidene finner du også oversikt over undervisningshagen med ulike ugressarter på Ås. Denne er oppdatert som besøkshage for publikum.
Forfattere
Lars Nesheim Gustav FystroSammendrag
The resources of rock phosphates are limited. Common use as P fertiliser has to be considered, both in environmental and economical perspectives. Applied superphosphate in many former plant nutrient investigations ruled out the possibility of consistent discussions of the separate S and P effects. The objective of the presented field experiments was to test how plant growth in grassland relates to proposed critical values of herbage P to N relationships. Three field trials were established on soils low in P. Five levels of P fertilisation (0, 5, 10, 20 and 50 kg P ha-1 yr-1) and two levels of N (normal and 50 % of normal) were applied. The trials were harvested in two subsequent years. Plant P uptake on unfertilised plots was higher then expected, and uptake of applied P was lower. Thus, the relation between relative dry matter yield and P/N in plants was not as detailed examined as planned, however, the yield decrease following low P/N was in accordance to our hypothesis. When 20 kg P ha-1 was applied only 14 % was found in the harvested material.
Forfattere
Tor Gunnar VågenSammendrag
Madagascar is often portrayed as a global environmental hotspot with widespread deforestation and environmental degradation. Quantitative and spatially explicit data on ecological change are, however, scarce and current estimates are often based on simplistic representations of deforestation and land use change. Significant uncertainties in current estimates therefore remain. The present study was conducted to assess deforestation and other important complex land use change trajectories in the eastern highlands of Madagascar. A timeseries of satellite imagery dating from 1972 to 2001 was used to analyse overall change and rates of change between different land use types in the study area. Forest cover in the study area was approximately 8060 ha in 1972 and 4278 ha in 2001. Rates of deforestation were not, however, constant throughout this period, but varied from 52 ha yr1 (1972"1992) and 341 ha yr1 (1992"1999). The increased rates in the 1990s were attributed to turbulent political conditions on the island during the latter period and shows the complex relationships between social, political and ecological processes governing deforestation and land use change processes. Accessibility (distance to villages and roads) and elevation were shown to be the most important predictors of deforestation risk in the study area. Intensive cultivation of slopes (tanety) increased by about 3400 ha ( 65%) during the study period, a significant part of which came from cultivation of grassland savanna (net increase 1700 ha). These trends were found to be indicative of increasing pressure on available land resources in the region, leading to extensive cultivation of marginal grasslands and ultimately significant soil fertility decline.
Forfattere
Bent Braskerud (permisjon)Sammendrag
Menneskelig aktivitet kan skape erosjon og grumset vann. Fangdammer lages for å bedre vannkvaliteten i bekker og redusere oppfyllingen av reservoar. Selv om anleggene er små og grunne, og vannets oppholdstid kort, viser langvarige undersøkelser at 50-70 % av partiklene kan fjernes på varig basis. Selv leire som normalt har lang bunnfellingstid holdes tilbake i de konstruerte våtmarkene. Denne artikkelen viser hvordan dette er mulig, og gir samtidig noen enkle råd om konstruering.
Forfattere
Trygve S. AamlidSammendrag
Ved etablering av økologisk engsvingelfrøeng bør vi så gjenlegget samtidig med / like etter dekkveksten og heller kutte ut ugrasharvinga. I middel for to forsøk i 2004/05 gav ni dagers utsettelse av såinga på grunn av blindharving henholdsvis 15, 20, 13 og 5% reduksjon i første års frøavling ved gjenlegg i bygg, vårhvete, grønnfôr av bygg/erter og erter til modning. Ugrasharving førte til mer kvitkløver i engåret, og gav heller ikke større dekkvekstavling i gjenleggsåret. Ved etablering av frøeng er det alltid viktig at dekkveksten ikke får for stort forsprang på gjenleggsplantene. Gjenlegg i grønnfor av korn og erter gav i disse forsøka gjennomgående større førsteårs frøavling enn gjenlegg i erter til modning, som igjen gav større frøavling enn gjenlegg i bygg eller vårhvete til modning. Det kunne imidlertid ikke påvises bedre nitrogentilgang til gjenleggsplantene etter gjenlegg i grønnfor og erter enn etter gjenlegg i bygg eller hvete. Unasett hvliken dekkvekst som velges er det derfoir viktig å høstgjødsle gjenlegget like etter at dekkveksten er høsta.
Forfattere
Sonja Klemsdal Oleif ElenSammendrag
Formål: Formålet med dette studiet var å utvikle en sensitiv deteksjonsmetode for Fusarium culmorum kontaminering i prøver av korn. Metoder og resulater: En nested-PCR metode der man bruker et enkelt lukket rør, ble utviklet for deteksjon av F. culmorum i infiserte kornprøver. Konsentrasjonen av det første primer paret ble fortynnet 10.000 ganger sammenlignet med konsentrasjonen for det andre primerparet. På grunn av Ulik annealingstemperatur ble både den første og den andre polymerase kjede reaksjonen (PCR) utført i to påfølgende reaksjoner i den samme lukkede mikrorøret. Deteksjonsgrensen var 5-50 fg av renset sopp DNA, noe som tillot deteksjon av 1% infisert hvetekorn i en blanding av uinfiserte korn. Konklusjon: F. culmorum kan spesifikt detekteres i kornprøver ved denne svært sensitive metoden med nested-PCR i et enkelt lukket mikrorør. Resultatets betydning: Dette arbeidet beskriver deteksjonen av F. culmorum i korn prøver ved en metode som er mer enn 100 ganger mer sensitiv enn tidligere beskrevede PCR metoder. Metoden involverer lav risiko for krysskontaminering mellom prøver, lave analysekostnader og redusert tidsforbruk sammenlignet med standard nested-PCR protokoller.
Forfattere
Jeanne Perceval Pierre Benoit Marianne Stenrød Ole Martin Eklo Marie-Paule Charnay Enrique BarriusoSammendrag
Metribuzin is commonly used in Norway for weed control in potato crop in rotation with spring barley production. Under temperate climatic conditions, metribuzin dissipation has been widely studied, but in nordic environment data are needed to assess quantitatively the dissipation fate and the risk of leaching. Laboratory incubation studies were conducted at 5, 15 and 28"C to evaluate the influence of temperature on the mineralization of metribuzin in two sandy loam soils sampled in southern and northern Norway and under a temperate climate in France for comparison purposes. Using 14C-labelled metribuzin, mineralization and the evolution of 14C-residues in soil could be observed during an incubation period of 49 days. Total metribuzin mineralization and organic carbon mineralization rates showed a positive temperature response in all soils. Metribuzin mineralization was low, but degradation products were formed and their abundance depended on temperature conditions. Investigation of soil microbial characteristics such as microbial biomass and general microbial activity indicated differences in the composition of the soil microbial population. The evolution of available 14C-metribuzin residues with time gave evidence of a strong temperature effect indicating that in such soils where sorption is weak, biodegradation processes have a major control on metribuzin mobility and persistence.
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.