Effects of long-term tillage systems on aggregate-associated organic carbon in the eastern Mediterranean region of Turkey

Abstract

The stability of aggregates plays a vital role in preserving and long term storing of soilorganic carbon (SOC). In this study, the long-term (2006-2014) effects of six tillagesystems on aggregate-associated SOC were investigated in a field experiment conductedunder Mediterranean conditions. The tillage treatments were; conventional tillage withresidue incorporated in the soil (CT1), conventional tillage with residue burned (CT2),reduced tillage with heavy tandem disc-harrow (RT1), reduced tillage with rotary tiller(RT2), reduced tillage with heavy tandem disc harrow fallowed by no-tillage (RNT) forthe second crop, and no tillage (NT). The most frequently encountered aggregates in alltillage systems were at 4.0-2.0 mm size and the least frequently found aggregates were1.0-0.5 mm. The mean weight diameter (MWD) value increased in the NT compared tothe conventional tillage practices at the rates of 137% and 204%, respectively at 0-15cm soil depth. Aggregate-associated SOC contents in 0-15 cm depth were higher underconservation tillage systems. However, the highest SOC at 15-30 cm depth were greatermainly in conventional tillage systems as 9.4% for both CT1 and CT2. The resultsindicated that conservation tillage systems had greater aggregation and carbon storageat the soil surface.