Conservation tillage research indicated that continuous use of no-tillage or shallow tillage causes an increase in soil dry bulk density, in weed infestation and reduced yields. In a four-year experiment in Greece in a clay loam soil, five tillage methods using plough, heavy cultivator, rotary cultivator, disk harrow and no-tillage for primary tillage were compared. The adverse effects of conservation tillage mentioned were observed. During the experiment all crop residues were incorporated into the soil. In order to study the effect of using deep soil loosening in conservation tillage plots a change in tillage was made such that plots with continuous five yearof a tillage system can be compared to plots with four years of each studied treatment and for the fifth combination of all others. The results of the experiment showed that conservation tillage methods increased weed infestations. Ploughing for a year decreased weed populations. Five years of no tillage caused an increase of soil dry bulk density to 1.60 g/cm3 compared to 1.12 g/cm3 for conventional tillage. Deep soil loosening after four years reduced dry bulk density considerably. Soil organic matter at a depth 0-10 cm increased after five years of no tillage to 2.78 % compared to 1.56% of conventional tillage and around 1.2 % at the beginning of the experiment. At depth 10-20 cm conventional tillage had 1.77% organic matter compared to 1.33% for no tillage. Year 2001 was a very dry one and reduced tillage methods had the best plant emergence with ploughing and no tillage giving the lower emergence rates. But at the end of the period ploughing gave the best yields.