Conservation or reduced tillage may be a promising practice in soil management to improve soil properties and crop production for the planting of spring crops in the Plains of Troy in the Southwest Marmara Region of Western Turkey. The introduction of these tillage practices in soils that are naturally poor in organic matter could reduce soil degradation under intensive agricultural management in the area. Therefore, a 2-yr field experiment (2006 and 2007) was conducted to study the effect of two types of conservation or reduced tillage [shallow tillage (ST) with rototiller and chisel tillage (CT)] and conventional tillage with mouldboard plough (MT) on bulk density, penetration resistance, water content, oxygen diffusion rate and crop yields in a clay loam soil cropped with spring maize following winter vetch. Over a 2-yr average, penetration resistance was similar at the 0-15 cm depth in all tillage treatments in both growing years, while it was lower in CT and ST compared with MT at a depth of 15-30 cm, but never reached 2.50 MPa, which is considered limiting for root growth. Bulk density values over a 2-yr average were 1.35, 1.36 and 1.33 Mg m(-3) for MT, ST and CT, respectively, during the growing seasons at a soil depth of 20-30 cm. No oxygen diffusion rate values were observed below the 17.0 mu g m(-2)s(-1) reported as the threshold level to inhibit root growth in maize at any time of the growing seasons and using the various tillage treatments. Soil water content was found to be higher in ST than in MT and CT at all depths throughout the 2006 growing season, while it was similar in all tillage treatments in the 2007 growing season. ST also produced grain yield as much as MT in 2006, while the differences among tillage systems were nonsignificant in 2007.