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
H.B GjærumSammendrag
Twenty-eight rust taxa, one new to Yukon,some hosts new to Alaska
Sammendrag
Velkommen til Planteforsk litteraturdatabase/ Welcome to Planteforsk Literature Database Tittel/Title: Genetic variability of Phytophthora infestans in Norway and Finland as revealed by mating type and fingerprint probe RG57 Publikasjon: Publication: Mycological Research Volum (Nr): Volume (No.): 103(12) Side: Page: 1609-1615 Utgitt: Published: 1999 Forfatter(e): Author(s): Brurberg, M.B., A. Hannukkala & A. Hermansen Enhet: Research station: Planteforsk Plantevernet Nøkkelord: Keywords: Plantevern, Phytophthora infestans, tørråte, krysningstype, DNA fingerprinting Sammendrag: Abstract: Mating type and RG57 fingerprints were determined for 141 isolates of Phytophthora infestans collected from 63 different fields in all important potato growing areas in Norway and Finland. Seventy-six multilocus genotypes were identified, of which 53 were detected only once. Norwegian and Finnish isolates were similar in terms of genotypic diversity and the genetic distances between the genotypes. The large number of genotypes and the high genetic distances between the genotypes indicate that sexual reproduction is contributing significantly to the genetic variation of P. infestans in Norway and Finland. ISBN: - ISSN: - Pris: Price: - Bestilling: Ordering: - Merknad: Notes: vit44 eng61 pl1 pv21
Forfattere
Trond Henriksen T.A BrelandSammendrag
On twelve occasions during a two-year field experiment, we determined the decomposition of barley straw, ryegrass foliage, white clover foliage, potato haulm and white cabbage leaves confined in buried mesh bags that were protected against leaching. After one year, 49, 18, 8, 25 and 5 % of initial carbon (C) in the five crop residues remained, respectively. The corresponding figures for nitrogen (N) were 105, 32, 8, 36 and 11 %. The data were used to evaluate a simulation model developed during previous studies of crop residue C and N turnover under controlled temperature and moisture conditions. Description of plant residue degradability and model parameter values were taken from these studies. Rate-modifying functions were then added to take account of effects of measured soil temperature and moisture. The model gave a good overall description of crop residue degradation but slightly underestimated C release and, to a greater extent, N release during the first autumn and winter. The relatively rapid N loss in this period, suggested that low temperatures restricted microbial N immobilization more than it did gross decomposition. We hypothesized that this was caused by a reduced microbial growth yield efficiency (E) at low temperatures. When we reduced the value of E from 0.5 (default value) to 0.2 at 2 °C and below, model fit to C and N mineralization was improved substantially. Moreover, the model produced an excellent fit to remaining wheat straw C and a gave good description of N mineralization in an independent experiment, indicating that reducing the value of E was justified. The results suggested that crop residue degradability and the decomposer community were reasonably described in the model, that the rate-modifying functions of temperature, moisture and N availability were sound and that parameter values set under controlled conditions represented field conditions also, possibly except that of E.
Forfattere
Trond Henriksen T.A BrelandSammendrag
Good predictions of plant litter carbon (C) and nitrogen (N) turnover in soil depends heavily on a reliable quantification of litter quality. In this work, eight common agricultural crop residues were described by their intrinsic chemical properties and incubated in a sandy soil (15°C and "0.01 MPa water potential). Measured C mineralization varied greatly between the plant materials and was well predicted by a simulation model in which litter C is subdivided into three pools according to the results of stepwise chemical digestion (Van Soest analysis). Nevertheless, there was a significant lack of fit for some of the materials. This was caused by differences in the specific decay rates of holocellulose-like substances (kSPM) as subsequently estimated for each plant material by fitting the model to data on remaining holocellulose. Even though the model takes account of microbial N deficiency, the optimized kSPM values were significantly correlated with initial N (r2 = 0.93) but not with lignin concentration. To test the predictive value in our model of indices and quantities thought to be related to litter degradability, we investigated whether they were correlated with the kinetically defined pool of readily decomposable plant constituents as estimated by fitting the model to measured C mineralization rates. Neutral detergent-soluble C (Van Soest analysis) was best correlated with the estimated pool (r2 = 0.78) followed by water-soluble C (r2 = 0.69) and C digestible in vitro in rumen fluid (r2 = 0.66). Measured C/N ratio in holocellulose-like substances was highly correlated with the overall C/N ratio of the plant materials (r2 = 0.96). In the model, we describe the degradability of litter N on the basis of the measured C/N ratios of the litter pools. The simulated microbial N requirement is governed by a successive replacement of rapidly growing organisms with a low C/N ratio by more slowly growing organisms with a slightly higher C/N ratio, reflecting the commonly observed increase along the decay continuum in the fungal contribution to microbial activity. This model feature was supported by a measured tendency to an increasing biomass C/N ratio. The model gave unbiased simulations of N mineralization and microbial biomass N. This indicates that the descriptions of litter N availability and microbial N requirement in the model were reasonable. However, significant discrepancies between simulated and measured values occurred for some of the plant materials during the first few days of decomposition, emphasizing the need for more accurate knowledge for this very dynamic phase. Our results suggest that an a priori characterization of litter degradability is possible in our model by the use of stepwise chemical digestion for subdivision of litter C and N combined with measurements of initial N to set the decay rate constant of holocellulose-like materials.
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