Estimated N leaching losses for organic and conventional farming in Denmark

The impact of organic compared to conventional farming practices on N leaching loss was studied for Danish mixed dairy and arable farms using an N balance approach based on representative data. On mixed dairy farms a simple N balance method was used to estimate N surplus and N leaching loss. On arable farms the simple N balance method was unreliable due to changes in the soil N pool. Consequently, the FASSET simulation model was used to estimate N surplus, N leaching loss and the changes in the soil N pool. The study found a lower N leaching loss from organic than conventional mixed dairy farms, primarily due to lower N inputs. On organic arable farms the soil N pool was increasing over years but the N leaching loss was comparable to conventional arable farms. The soil N pool was primarily increased by organic farming practices and incorporation of straw. The highest increase in the soil N pool was seen on soils with a low level of soil organic matter. The level of N leaching loss was dependent on soil type, the use of catch crops and the level of soil organic matter, whereas incorporation of straw had a minor effect. N leaching was highest on sandy soils with a high level of soil organic matter and no catch crops. The study stresses the importance of using representative data of organic and conventional farming practices in comparative studies of N leaching loss

Fusion, Crossing and Monodromy in Conformal Field Theory Based on SL(2)SL(2) Current Algebra with Fractional Level

Based on our earlier work on free field realizations of conformal blocks for conformal field theories with $SL(2)$ current algebra and with fractional level and spins, we discuss in some detail the fusion rules which arise. By a careful analysis of the 4-point functions, we find that both the fusion rules previously found in the literature are realized in our formulation. Since this is somewhat contrary to our expectations in our first work based on 3-point functions, we reanalyse the 3-point functions and come to the same conclusion. We compare our results on 4-point conformal blocks in particular with a different realization of these found by O. Andreev, and we argue for the equivalence. We describe in detail how integration contours have to be chosen to obtain convenient bases for conformal blocks, both in his and in our own formulation. We then carry out the rather lengthy calculation to obtain the crossing matrix between s- and t-channel blocks, and we use that to determine the monodromy invariant 4-point greens functions. We use the monodromy coefficients to obtain the operator algebra coefficients for theories based on admissible representations.Comment: 42 Pages, LaTeX, uses pictex.sty, alternatively prepictex.tex, pictex.tex, postpictex.te

Impact of organic pig production systems on CO2 emission, C sequestration and nitrate pollution

Organic rules for grazing and access to outdoor area in pig production may be met in different ways, which express compromises between considerations for animal welfare, feed self-reliance and negative environmental impact such as greeehouse gas emissions and nitrate pollution. This article compares environmental impact of the main organic pig systems in Denmark. Normally sows are kept in huts on grassland and finishing pigs are being raised in stables with access to an outdoor run. One alternative practised is rearing also the fattening pigs on grassland all year round. The third method investigated was a one-unit pen system mainly consisting of a deep litter area under a climate tent and with restricted access to a grazing area. Using life cycle assessment (LCA) methodology, the emissions of greenhouse gasses of the all free range system was estimated to be 3.3 kg CO2-equivalents kg-1 liveweight pig, which was significantly higher than the indoor fattening system and the tent system yeilding 2.9 and 2.8 kg CO2-eq. kg-1 pig respectively. This was 7-22% higher compared with Danish conventional pig production but, due to the integration of grass-clover in the organic crop rotations these had an estimated net soil carbon sequestration. When carbon sequestration was included in the LCA then the organic systems had lower green house gas emissions compared with the conventional pig production. Eutrophication in nitrate equivalents per kg pig was 21-65% higher in the organic pig systems and acidification was 35-45% higher per kg organic pig compared with the conventional system. We conclude that even though the all free range system theoretically has agro-ecological advantages over the indoor fattening system and the tent system due to a larger grass-clover area this potential is difficult to implement in practice due to problems with leaching on sandy soil. Only if forage can contribute a larger proportion of the pigfeed-uptake may the free range system be economically and environmentally competitive. Improvement of nitrogen cycling and efficiency is the most important factor for reducing the overall environmental load from organic pig meat. Presently a system with pig fattening in stables and concrete covered outdoor runs seems to be the best solution from an environmental point of view

Simulating leaching losses following incorporation of grass and grass-clover leys

Dynamic simulation models can be useful tools for predicting the residual effect of leys, but only if they have been calibrated and validated appropriately for this particular situation. The BIOMOD project has aimed at expanding, calibrating and validating two Danish dynamic simulation models, namely FASSET and Daisy, for a range of crop rotational situations occurring in organic farming. Here we report on the calibration results for an extensive experiment with residual effect and nitrate leaching following grass-clover leys

Hvordan bliver fagdidaktiske værktøjer fra læreruddannelsen til en del af læreres undervisningsfaglighed?

Artiklen præsenterer en kvalitativ undersøgelse af hvordan fagdidaktiske værktøjer fra natur/teknik gav mening for fire erfarne lærere som tog et ekstra linjefag. Problemstillingen afdækkes medinddragelse af overvejelser over hvilke faktorer der er i spil når lærere udvikler deres undervisningsfaglighed(PCK). Resultater med afsæt i analyserede interviewdata viser at de fagdidaktiske værktøjerisær gav mening hvis de blev udfoldet i en specifik faglig undervisningssammenhæng. Anerkendelseeller anbefaling fra kolleger ser ud til at spille en rolle for læreres efficacy og villighed til at afprøvenyt. Desuden har det betydning at læreren relativt hurtigt får mulighed for at afprøve værktøjer ogmed relativ succes. I den fremadrettede perspektivering refereres der til hvordan dette må få betydning for hvorledesvi driver læreruddannelse. This qualitative study seeks to investigate how pedagogical methods from Science& Tech nology specialization make sense to four experienced teachers inrelation to their teaching practice. It was revealed by analysis based on a PCKmodel: “model for teacher learning”. Especially Content Representation (CoRe)and Pedagogical and Professional experience Repertoire (PaP-eR) are appreciated,and the questions derived from CoRe’s challenge the teachers to recall and experimentwith the pedagogical tools in their teaching practice. The pedagogical toolsespecially make sense to the teachers if they are presented in relation to specificscience subject matter, but it depends on the student teachers’ and colleagues’beliefs about teaching and learning. The teachers’ possibility to experiment andevaluate the pedagogical tools relatively shortly after introduction has greatimportance. Looking forward, these results should influence approaches takenin teacher education