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
Myrjord dekker 2-3 % av verdens landareal og inneholder ca en tredel av jordas lager av organisk karbon og omtrent like mye carbon som i atmosfæren. Drenering og dyrking av myr fører til en mineralisering av organisk materiale. Denne artikkelen omhandler emisjon av drivhusgasser fra dyrket myr i Nord-Norge. CO2-emisjonen økte med temperaturen, mens tilsvarende effekt ikke kunne påvises for N2O- og CH4-emisjonen. Estimert netto emisjon av drivhusgasser fra rør-grøftet myr var ca 2,2 kg for CO2, 0,03 kg for CH4 og 0,13 kg for N2O, uttrykt i CO2-ekvivalenter. Netto C-tap var ca 0,6 kg C per m2 og år. Karbontap kan derfor betraktes som jordforringelse når en tar hensyn til klimagassemisjonen. Resultatene viste betydningen av CO2-emisjonen fra dyrket myr i nord, som var ca 17 ganger høyere enn N2O-emisjonen som CO2-ekvivalenter.
Forfattere
Audun KorsæthSammendrag
Soil mapping by means of the EM38 device is offered commercially in many countries. The most common way to perform the mapping in the field is to tow the instrument on a sled behind a terrain vehicle. This normally involves mounting the instrument at a certain height h above the ground. The measurements of ECa with EM38 are, however, strongly affected by this height. The objective of this research is to find a simple but robust method to correct for the height at which the EM38-measurements were made. Measurements with EM38 were conducted in an field trial with alternative fertilizer applications (0, 60, 90, 120 and 150 kg N ha-1) to spring barley, at two sites with morainic loam in SE Norway; Apelsvoll Research Centre (60°42"N, 10°51"E) and Kise Research Station (60°46"N, 10°48"E). Two weeks after sowing/fertilization in spring 2003 (May 27), ECa was measured at both sites on all five treatments in three of the 20 replicate blocks on the ground and at 20, 40 and 60 cm above the soil surface. In conclusion, the correction functions presented offer theoretical models to correct EM38-measurements when measuring at an instrument height of 20 cm above the ground surface, a height which is within the interval of what is commonly used in practice for mobile operation of the device.
Forfattere
A.P. Maerere E.R. Mgembe S. Mwaitulo M.W. Mwatawala L.T. Nsemwa A. Ndunguru Carl Jonas Jorge Spetz May-Guri Saethre E.M. Senkondo E. Rwambali K.K. MwajombeSammendrag
A survey was conducted in Morogoro, Mbeya and Coast regions, using a structured questionnaire and field visits, to evaluate the diversity of banana grown, distribution systems of banana planting materials, agronomic and pest management practices and gender characteristics of banana production. A total of 108 households were interviewed in 11 villages. The interviewees consisted of 78.7% males and 21.3% females. Banana cultivars grown were diverse and use being different and more or less location specific. 24.3% of respondents grow cultivar Mtwike and 18.7% grow cultivars Mzuzu as their most important varieties, 16.7%, 9.8%, and 14.7% grow Mzuzu, Mtwike and Uganda, respectively, as their second most important varieties. In respect to variety characteristics, 22.9% preferred varieties with big bunches, 19% early maturing, 14.3% marketable, 10.5% long fingers and 9.5% with high resistance to pests. The main sources of banana planting materials for farmers are neighbours (60%) and Sokoine University of Agriculture (22.4%). About 17.3% obtain planting materials from their own fields, 19.6% use in-vitro materials and 80.4% use conventional materials. Few farmers (37.2%) received training on banana production with 22.7% trained at SUA. Farmers were not able to name pests attacking the crop. However, cultivars Mtwike, Kambani, Uganda and Matoke are considered to be more prone to pests. About 54.5% of the farmers use uprooting as a major pests control measure while 27.3% and 9.1% use chemicals and field sanitation measures, respectively. 51.1% apply organic fertilizers, 56.2% use bamboo as propping material. Gender role is very much pronounced in decision-making. For most activities, men featured as the decision makers. Land preparation is men"s activity (69.3%). Introduction of new cultivars that will be resistant to pests, training in cultural practices and establishment of centres for distribution of appropriate planting materials were considered to be important interventions required by farmers.
Sammendrag
The occurrence of Fusarium (represented by Fusarium spp. and Microdochium nivale) has been recorded in barley, oats and spring wheat seeds in Norway since the 1970-ies as part of the seed quality assessment. Annually a large number of samples representing both certified and farm saved seed from all cereal growing areas, was tested (100 or 200 seeds from each sample) at the Seed Testing Laboratory using the freezing blotter, the Doyer filter paper, and/or the agar plate (PDA) methods. In total, almost 30 000 samples of barley, more than 16 000 samples of oats and more than 9 000 samples of spring wheat were tested. The Fusarium frequencies were recorded in each sample, a mean of all samples was calculated each year for each cereal species, and multiple regressions with weather data from the growing season and also the Fusarium incidences in seed the previous year, were carried out. 69 % of the variation of the incidence of Fusarium in barley seeds was explained by 1) precipitation in July, 2) the incidence of Fusarium the previous year (both significant positive effects), and 3) precipitation in June, 4) temperature in July (both significant negative effects). In oat seed, precipitation in July and incidence of Fusarium the previous year explained 59 % of the variation. In spring wheat, as for barley and oats, precipitation in July and the incidence of Fusarium the previous year contributed positively, whereas precipitation in May and temperature in August had a negative effect.These four factors contributed significantly by 58% to the variation of Fusarium in spring wheat seed. It is concluded that the incidence of Fusarium in seed the previous year and precipitation in July were the main factors affecting the incidence of Fusarium in cereal seeds in Norway.
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
The performances of the plum rootstocks Ferlenain, Ishtara, Jaspi and P 8-13 compared with St. Julien A as a standard, for the cultivars `Opal" and `Reine Claude GF 1119" were assessed in a field trial in western Norway at 60° North. This trial was one part of an international plum rootstock trial located in seven European countries and organized from INRA Bordeaux. Trees were planted in spring 1994; spaced 2.0 x 4.0 m and formed with a central leader as free spindles. Soil management was grass in the alleyways and herbicide strips 1-m wide along the tree rows. Tree vigour, yield, fruit size and yield efficiency were evaluated for the seven subsequent years. Tree size was significantly affected by the rootstocks. P 8-13 produced the largest trees for both cultivars as measured by trunk cross-sectional area. The smallest trees were produced on Ferlenain for the cultivar `Opal" and on Jaspi for `Reine Claude". The cultivar `Opal" was the most productive and gave three times larger crop than "Reine Claude" on average for the six cropping years. The `Reine Claude" trees came two years later into production than `Opal". There were small differences between the different rootstocks in productivity: However, the rootstock Ferlenain produced significant lower crop than the other rootstock for `Opal". Trees on Jaspi were the most yield efficient for `Opal" and Ferlenain for `Reine Claude". The fruit sizes were in general medium to small for both cultivars and became little affected by the different rootstocks. The average fruit size was about 30 g for `Opal" and 25 g for `Reine Claude". Fruit quality characterized by the content of soluble solids was high for `Reine Claude" with average 20 % and 15 % for `Opal" and did not differ much between trees on the various rootstocks.
Forfattere
Morten GuntherSammendrag
Denne rapporten presenterer resultatene fra ti år med vannfuglregistreringer i Pasvik naturreservat. Til sammen er det gjennomført 31 tellinger i perioden 1996-2005 (20 om våren og 11 om høsten). 52 arter av vannfugler er registrert under tellingene, 16 av disse er oppført på Norsk Rødliste 2006. Antall registrerte individer har variert mellom 334 og 1056 om våren, og 324 og 1147 om høsten.
Sammendrag
Because light is assumed to suppress sporulation of many downy mildews (DM), it is a common component in forecast models. We evaluated effects of light intensity and quality, temperature, and diurnal periodicity on sporulation of Bremia lactucae, the causal agent of lettuce DM. We found that suppression of sporulation by light was strongly dependent upon temperature; with little suppression by light below 10 ºC. The greatest suppression of sporulation occurred at 400-450 nm, although a lesser effect was detected at 450-550 nm. At 15 ºC, a diurnal pattern of sporulation was observed independent of light and darkness. Current forecast models for lettuce DM use sunrise and sunset to delimit the hours during which leaf wetness and high RH can induce sporulation. Our results indicate that effects of short nights and extended twilight conditions, as in Nordic countries, should be incorporated into forecast models. Also, temperature should modify model predictions of sporulation, as the suppression of sporulation by light may be greatly reduced at temperatures below 15-20 ºC. The diurnal rhythm could interact with light and temperature to confound the results of controlled environment studies, and may be the controlling factor in timing of sporulation at low temperatures.
Sammendrag
The stiffest rods will create the longest casts! This is a common assumption made by many fly casters, but is it really accurate? What follows are the results of a test that examined this hypothesis by combining length measurements of rod stiffness using the Common Cents System (CCS). The test utilized eigth casters, all of them whom cast eight rods. Each caster made four casts with each rod. The article originally appeared in the Norwegian magazine "Alt om Fiske" in October 2006
Sammendrag
Det er ikke registrert sammendrag