Tor Arvid Breland

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We studied C and N mineralisation patterns from a large number of plant materials (76 samples, covering 37 species and several plant parts), and quantified how these patterns related to biological origin and selected indicators of chemical composition. We determined C and N contents of whole plant material, in water soluble material and in fractions(More)
The effect of roots on microbial growth and N immobilization was investigated in a pot experiment with barley, Italian ryegrass, and white clover. We used a silty subsoil with a low soil organic matter content (0.16%C and 0.012%N), which allowed us to measure N immobilization as an increase in total soil organic N (planted versus unplanted). At sampling,(More)
Knowledge about the mineralization dynamics of plant material added to soil is essential in order to predict potential effects on off-season N losses and N uptake by subsequent crops. Among the factors that may influence mineralization is the degree of contact with the soil matrix, as determined by the extent of mixing when plant material is incorporated.(More)
Predictive models of the temporal mineralization pattern of organic residues may help in development of strategies to synchronize N mineralization with the crop demand and minimize off-season losses. In the present investigation, two double first-order models with temperature as a driving variable were tested against data on decomposition and N(More)
The degree of contact between crop residues and the soil matrix, as determined by the method of residue incorporation, affects decomposition dynamics both under natural and experimental conditions. In microcosm experiments we tested the hypothesis that poor residue-soil contact reduces the decomposition of structural plant constituents through delayed(More)
 In a cropping systems experiment in southeastern Norway, ecological (ECO), integrated (INT) and conventional (CON) forage (FORAGE) and arable (ARABLE) model farms were compared. After 5 experimental years, topsoil was sampled in spring from spring grain plots and incubated for 449 days at controlled temperature (15  °C) and moisture content (50%(More)
The objective of the present work was to develop a method to distinguish between metabolically inactive and active parts of plant roots. White clover (Trifolium repens L.) roots were stained with 2,3,5-triphenyltetrazolium chloride (TTC) followed by root colour classification with an interactive scanner-based image analysis programme (WinRHIZO). Roots(More)
We applied a mechanistic ecosystem model to investigate the production and environmental performances of (1) current agricultural practice on two fields of a stockless organic cereal farm in southeast Norway and (2) alternative cereal-ley rotations and plowing time scenarios. Scenarios were simulated using historic weather data and a climate change(More)
In order to improve the basis for utilising nitrogen (N) fixed by white clover (Trifolium repens L.) in northern agriculture, we studied how defoliation stress affected the N contents of major plant organs in late autumn, N losses during the winter and N accumulation in the following spring. Plants were established from stolon cuttings and transplanted to(More)
A mechanistic dynamic model (Verberne et al. 1990) was used to simulate mineralization of white-clover materials in a loam (25% clay) and a sandy loam soil (5% clay). I tested the model‘s ability to simulate the observed temporal patterns and to take account of altered physical protection as affected by soil compaction or spatial residue distribution. With(More)