Effect of biowaste compost and nitrogen fertilization on macroporosity and biopores of Molli-gleyic Fluvisol soil**

The aim ofthis study was to evaluate the follow- up effect of biowaste compost on the structure and macroporosity of soil two years after compost application. The results were compared with mineral nitrogen fertilization and untreated control. A long-term crop rotation experiment was established on a silty loam Molli-gleyic Fluvisol in eastern Austria. In the 13-year field experiment different rates of compost and nitrogen fertilizers were applied. The compost used was source-separated organic house- hold waste compost at rates of 7, 13 and 18 t ha -1 year -1 on average. Nitrogen fertilization was applied to supply 27, 47 and 64 kg N ha -1 year -1 on average. Undisturbed soil samples were collected in March 2005 and July 2005 from the 10-20 cm soil layer, and charac- teristics of macropores were determined with special focus on biopores content. Results showed that the long-term application of compost and nitrogen fertilizer in the investigated soil did not cause any signi- ficant influence on macropore volume. The only effect of compost and nitrogen fertilization was observed in biopores content. Nitrogen fertilization increased participation of biopores of 1000-2000 m and 2000-4000m in diameter with respect to control and compost treatment. This effect can be ascribed to higher plant biomass production at the nitrogen fertilization treatment.