Mean weight diameter and water holding capacity of aggregates under contrasting soil tillage systems
Mert Acar1 1 2 1
1 2
Aggregate stability and organic matter are key attributes in minimizing detrimental impacts of agricultural practices and sustaining soil and environmental quality. Long-term (2006-2014) effects of six different tillage systems on aggregate size distribution and water holding capacity were investigated in a soil contained approximately 50% 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). Soil samples were collected from 0-15 and 15-30 cm soil depths, and characterized for aggregate size distribution, field capacity (FC), wilting point water content (WP) and available water content (AW). The most frequently encountered aggregates in all tillage systems were at 4.0-2.0 mm size and the least frequently found aggregates were 1.0-0.5 mm. Conservation tillage systems increased the rate of >4.0 mm and 4.0-2.0 mm macro-aggregates compared to conventional tillage systems. The average mean weight diameter (MWD) value increased in the NT
compared to the conventional tillage practices (CTS and CTB) at the rates of 137% and 204%, respectively at 0-15 cm soil depth. The MWD value in CTS (0.37 mm) was greater than the CTB (0.29 mm) treatment at 0-30 cm in which the stubbles burnt. Tillage systems had significant effects (P<= 0.01) on FC, WP and AW of soils. The highest AW in 0-15 cm was obtained with RNT (17.3%) and fallowed by RTD (14.2%) and RTR (13.2%). Similar responses were obtained for subsurface soil in terms of FC, WP and AW. The results revealed that
conventional tillage practices lead the degradation of physical characteristics of soils which significantly reduce the water holding capacity. Whereas, minimum tillage practices have been shown to enhance soil aggregation and water holding capacity of soils.
Keywords: tillage systems, conventional, conservation, aggregate stability, field capacity, available water
