Effects of different cover crop treatments, mechanical cultivation and herbicide treatment on soil quality parameters and yield of a hazelnut orchard located in Samsun province of Turkey were investigated. Festuca rubra subsp. rubra (FRR), Trifolium repens (TR), Festuca arundinacea (FA), T repens (40%) + F. rubra rubra (30%) + F. Arundinacea (30%) mixture (TFF), Vicia villosa (VV) and Trifohum meneghinianum (TM) cover crops were used in a hazelnut orchard with clay loam soils. Experiments also included mechanical control (MC), herbicide control (HC) and bare control (BC) treatments. Soil samples were taken from two depth (0-20, 20-40 cm) to analyses for soil quality parameters. It was observed that cover crops improved soil quality variables at the 0-20 cm soil depth. Cover crop applications rised the organic matter (OM) content from 2.28% for bare soil to 3.64% for the VV application. Rises in OM content due to different cropping regimes were obtained in the following order: HC< BC< MC< FA< FRR< TM< TFF< TR< VV. VV application compared with the other applications determined the highest rises in OM (59.7%), total porosity (10.9%), saturated hydraulic conductivity (161.2%), aggregate stability (9.9%), electrical conductivity (68.6%) and the largest decrease in bulk density (11.7%). While the highest mean hazelnut yield (1516 kg ha(-1)) was found in the VV, the lowest mean hazelnut yield (1337 kg ha(-1)) was obtained with in the MC. Cover crops, especially VV and TR treatment, may be incorporated into cropping systems to improve soil quality variables and hazelnut yield.