Effect of changing tillage practices after four years of continuous reduced tillage

Conservation tillage research indicated that continuous use of no-tillage or shallow tillagecauses an increase in soil dry bulk density, in weed infestation and reduced yields. In a four-yearexperiment in Greece in a clay loam soil, five tillage methods using plough, heavy cultivator, rotarycultivator, disk harrow and no-tillage for primary tillage were compared. The adverse effects ofconservation tillage mentioned were observed. During the experiment all crop residues wereincorporated into the soil. In order to study the effect of using deep soil loosening in conservationtillage plots a change in tillage was made such that plots with continuous five yearof a tillage systemcan be compared to plots with four years of each studied treatment and for the fifth combination of allothers. 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 anincrease of soil dry bulk density to 1.60 g/cm3 compared to 1.12 g/cm3 for conventional tillage. Deepsoil loosening after four years reduced dry bulk density considerably. Soil organic matter at a depth0-10 cm increased after five years of no tillage to 2.78 % compared to 1.56% of conventional tillageand around 1.2 % at the beginning of the experiment. At depth 10-20 cm conventional tillage had1.77% organic matter compared to 1.33% for no tillage. Year 2001 was a very dry one and reducedtillage methods had the best plant emergence with ploughing and no tillage giving the loweremergence rates. But at the end of the period ploughing gave the best yields.