Organic carbon distributions in aggregates under different tillage practices in mediterranean conditions
Mert Acar1 1, Hikm 2, Zeliha Bereket Barut1
1 2
The stability of aggregates plays a vital role in preserving and long term storaging of soil organic carbon (SOC). Thus, impacts of contrasting tillage systems on SOC have been of particular interest. In this study, long-term (2006-2014) effects of six tillage systems on SOC of different sized aggregates were investigated in a field experiment conducted under
Mediterranean conditions in Adana, Turkey. Field experiment was established on Arik soil that contains over 50% smectitic clay. The tillage treatments were; Conventional tillage with stubble (moldboard plowing) (CTS), Conventional tillage with stubbles burned (CTB), Heavy disc harrow reduced tillage (RTD), Rototiller reduced tillage (RTR), Heavy disc harrow zero soil tillage (RNT) and no till or zero tillage (NT). Tillage systems had significant effects (P<=0.01) on SOC stored in different size aggregates. The highest SOC at >4.0 mm size aggregates were in NT (1.37%) and RTR (1.35%), respectively. The aggregates with the highest SOC content in 0-15 cm were at 1.0-0.5 mm size and the aggregates with lowest organic C content were at 2.0-1.0 mm size. Aggregate-associated SOC contents in 0-15 cm depth were higher under
conservation tillage systems compared to the conventional tillage systems. Turnover effect of conventional tillage induces microbial activity and increases decomposing of organic matter in soil which resulted in lower SOC in surface soil. The effect of tillage systems in 15-30 cm was only significant for >4.0 mm size aggregates. The highest SOC at 15-30 cm depth were greater mainly in conventional tillage systems as 0.94% for both CTS and CTB. The results indicated that no-till and reduced till systems had greater aggregation and carbon storage at the soil surface but only CTB and CTS increased aggregation below the surface.
Keywords: Soil tillage systems, soil organic carbon, carbon sequestration, aggregate size, conservation, conventional
