Abstract
Throughout the world, degradation of soil has become an environmental problem which limits the sustainability of agriculture and decreases soil productivity. The main reason of degradation is either over cultivation or the utilization of improper tillage methods. Therefore, tillage practices play a crucial role in chemical, biological and physical properties of agricultural soils. This role was determined often by using indicators of soil quality such as bulk density, aggregate stability, plant available water, organic carbon content, soil compaction and other properties. The aim of this field study was to examine the effects of different tillage systems on some soil characteristics in the semi-arid Mediterranean coastal plain of Turkey. In the research, the following six different tillage systems were tested: conventional tillage with residue incorporated (CTR), conventional tillage with residue burned (CTB), minimum tillage with heavy tandem disc harrow (MTD), minimum tillage with rotary tiller (MTR), minimum tillage with heavy tandem disc harrow for the first crop + no-tillage for the second crop (MNT), and no tillage (NT). The experiment was initiated with summer soybean, followed by winter wheat and summer corn and ended with winter wheat production. Bulk density, aggregate stability, organic matter content and soil penetration resistance were evaluated as indicators of soil quality in this study. Conservation tillage systems (MT and NT) improved organic carbon content and aggregate stability of the soil. The different tillage systems showed a significant effect with respect to the amount of organic matter and aggregate stability in the soil. Organic matter values were lower (49-60%) under CT practices and residue burning accelerated the loss of organic carbon content. The highest aggregate stability values were found for NT (over 38%). Penetration resistance and bulk density of the tilled soils (CT and MT) were lower than in no-tillage plots (MNT and NT), bulk density was 1.26-1.32 g/cm3 in CT at all soil depths. The trials showed that, conservation tillage practices (MT and NT) can provide better soil characteristic values than conventional practices in the semi-arid soils of the Mediterranean coastal plain.
