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.
1999
Forfattere
Trond Henriksen T.A BrelandSammendrag
The objectives of our work were (1) to investigate the response of wheat (Triticum aestivum L.) straw decomposition to increasing nitrogen (N) availability (0.5, 0.8, 1.2 and 1.9% N of straw dry matter) in a microcosm experiment at controlled temperature (15°C) and moisture (-0.01 MPa), (2) to elucidate underlying mechanisms at the microbial-community level, and (3) to develop a model according to the measurements. Concentrations of available N (straw N and soil inorganic N) below 1.2% of straw dry matter significantly reduced the rate of carbon (C) mineralization from straw residues, and the growth of total soil microbial biomass (chloroform fumigation-extraction). The negative effects appeared shortly after the pool of soil mineral N had been depleted. The N effect on the microbial community was mainly caused by a reduced fungal growth (ergosterol), while total bacterial biomass (epifluorescence microscopy) was not significantly affected. However, number of cellulase-producing, colony-forming bacterial units decreased with decreasing N availability. In straw-amended soil, decreasing N concentrations reduced activities of exocellulase, endocellulase and hemicellulase, while in unamended control soil the effects were opposite. We developed a model in which three fractions of straw residues, determined by proximate analysis (Van Soest), and a humus pool were assumed to decay according to first-order rate kinetics. In accordance with the microbial measurements, the microbial community was subdivided into three groups consuming readily decomposable, structural and humus materials respectively. When holocellulose decay rate was modified as a function of N availability, the model simulated N effects on C mineralization and microbial biomass growth very well. Our experiment showed that wheat straw mineralization may be retarded at N concentrations well above those frequently found after grain harvest in the field and that effects of N availability should be taken into account when modelling C and N turnover in agricultural soils. Moreover, the trial exemplified a situation where studies of functional groups of decomposer organisms were required to explain and model satisfactorily differences observed at the process level.
Forfattere
Svein Solberg E BøeSammendrag
A survey among onion (Allium cepa L.) growers and extension officers in Toten, Norway, was carried out during the period 1981-1995. The study was used both to describe trends in onion crop management and to pinpoint some factors related to total post-harvest losses due to watery scales (WS). The occurence of WS increased during the first part of the 1980"s. Annual variations in watery scales can be explained by meteorological data. Years with high precipitation in August and September had the highest frequency of WS. A positive correlation between rainfall during the 3 last days of field curing and WS was found. High air humidity could also be ralated to high occurence of WS.
Forfattere
T.A Breland Ragnar EltunSammendrag
In a cropping systems experiment in south-eastern Norway, ecological (ECO), integrated (INT) and conventional (CON) forage (FORAGE) and arable (ARABLE) model farms were compared. After 5 years, topsoil was sampled in spring from spring grain plots and incubated for 449 days at controlled temperature and moisture content. There were no detectable differences between model farms in terms of total soil C or N. For INT and CON, however, values of microbial biomass C and N, microbial quotient, and C and N mineralization were, or tended to be, higher for FORAGE than for ARABLE. For ECO treatment, values were similar for FORAGE and ARABLE and did not differ significantly from that of CON FORAGE. For INT and CON, the metabolic quotient was lower for FORAGE than for ARABLE. Again, for the ECO treatment, values were similar for FORAGE and ARABLE and did not differ significantly from the CON FORAGE. We estimated the size of conceptual soil organic matter pools by fitting a decomposition model to biomass and mineralization data. This resulted in a 48% larger estimate for CON FORAGE than for CON ARABLE of physically protected biomass C. For physically protected organic C the difference was 42 %. Moreover, the stability of soil aggregates against artificial rainfall was substantially greater for CON FORAGE than for CON ARABLE. On this basis, we hypothesized that the lower microbial quotient in the FORAGE soils were mainly caused by a smaller proportion of active biomass due to enclosure of microorganisms within aggregates. Altogether, our results indicate a poorer inherent soil fertility in ARABLE than in FORAGE rotations, but the difference was small or absent in the ECO systems, probably owing to the use of animal and green manures and reduced tillage intensity in the ECO ARABLE rotation.
Forfattere
T.K Haraldsen Åsmund Asdal C Grasdalen Lars Nesheim T.N UglandSammendrag
Det er ikke registrert sammendrag
Forfattere
Bernt Olav HoelSammendrag
The aim of this study was to assess a quick test method determining nitrate in basal stem tissue sap for the prediction of nitrogen status in winter wheat (Triticum aestivum L.). Because of the large between-site and between-year variability, this study does not indicate that the method can be recommended for extended practical use
Forfattere
Trygve S. Aamlid J.T Foss J.O ForbordSammendrag
Det er ikke registrert sammendrag
Forfattere
Trygve S. AamlidSammendrag
Det er ikke registrert sammendrag
Forfattere
Trygve S. AamlidSammendrag
Det er ikke registrert sammendrag
Forfattere
Trygve S. AamlidSammendrag
Det er ikke registrert sammendrag
Forfattere
Trygve S. AamlidSammendrag
Det er ikke registrert sammendrag