The aim of this study was to determine whether organic and conventional cultivation systems differ with respect to baking quality of winter wheat and to evaluate the influence of seasonal variations on this parameter. The research site was at Kvinnersta, Central Sweden, on a clay loam containing 3-6% humus with a mean annual temperature of 5.7°C and a mean annual rainfall of 540 mm.A PCA analysis showed that differences existed between the cultivation systems. PC1 explained the greatest variation, 46%, and this was significant (P = 0.020). The factors affecting the variation most were the farinogram dough stability and bread volume. Rainfall during April afGärd L-Baeckström is Researcher, Please note that this electronic prepublication galley may contain typographical errors and may be missing artwork, such as charts, photographs, etc. Pagination in this version will differ from the published version. fected the conventional system and during April-June the organic. Univariate statistics showed that the conventional system was significantly better (P < 0.05) than the organic system with respect to: protein content, wet gluten, farinogram dough stability, dough breakdown, extensogram surface, dough yield, bread volume and yield. The overall outcome of the study was that nitrogen was the most limiting factor in the organic cultivation system.

Two field experiments were conducted from 1991 to 1996 on clay soils in central Sweden to provide information for improving soil fertility, minimizing N leaching, and increasing the benefits of ley to subsequent crops in organic farming. The results show that it is possible to calculate the amount of N mineralized during the 2-year period following incorporation of ley-crop residues, based on the proportion of incorporated organic matter stabilized in the more resistant humus fractions (i.e., the humification coefficient, calculated to be 35-40%), C:N ratios of the ley biomass, and ley age (humification appears to be higher in older crop residues). The fractions of potentially mineralizable N that are actually mineralized in the first and second years after ley incorporation vary depending on ley age and botanical composition and climatic conditions.

The effects of N dose and stage of ripeness on Fe, Co, Cr, Ni, Se and N concentration and incidence of fungal diseases were measured in winter wheat grain from conventional (CONV) and organic (ORG) systems on neighbouring areas of a 10-year-old manure-based farm. Principal components analysis (PCA) of the data showed that year had the greatest influence on the results, but that cropping system affected N, Ni, Fe and Se content and incidence of diseases. Attack by Dreschlera tritici-repentis was highest in ORG and attack by Stagonospora nodorum in CONV. Increasing stage of maturity increased incidence of fungal disease and Fe content. Analysis of variance and MANOVA showed that wheat yield was affected by weather (precipitation and temperature), cropping system and N dose. The 10% lower yield in ORG than CONV was explained by a lower amount of plant available N at the same N dose. Nitrogen, Fe, Ni, Se and Co contents in grain were affected by year, while dry matter content was significantly lower in ORG than in CONV. The MANOVA identified correlations between Co and Fe, Ni and Se. Incidence of fungal diseases was foremost affected by weather, stage of ripeness and N dose. Organic cropping increased Fe and Se uptake and decreased S. nodorum attack, but increased attack by D. tritici-repentis.

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