Irmak Yilmaz: Seasonal changes of some microbiological properties of soils in a field of hazelnut growing -253 -APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 18(1):253-262. Abstract. The aim of this study is to identify the effects of the compost obtained from hazelnut husks by using biological techniques, on soil quality at different sampling times. The composted hazelnut husk was used at 6 application doses and with 3 replications in order to increase the organic material content of the soils at

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... doses of 0, 0.5%, 1%, 2%, 3% and 4%. The hazelnut husk compost was applied at the Akçatepe/Ordu/Turkey experiment area on the 23rd of November 2012 by using the mattock planting method. The soil samples were collected from the field at 4 different sampling seasons and consequently, various chemical and biological soil characteristics were detected. The results shows; certain doses and different sampling seasons have a significant effect on the beta-glucosidase, urease and acid phosphatase enzyme activities in soils; the most effective doses were 4% and 3%; the 1st and 4th seasons provided the best results. As for other biological characteristics the highest values were as follows: CO2 production at 1% dose, microbial biomass-C value at 2% dose. The application of hazelnut husk compost, which has a rich organic matter content and is an organic material itself, to soils, promotes an increase in soil organic materials.