Soil loosening characteristics of a dual bent blade subsurface tillage implement

•A forward dual-bent blade can be suggested as a suitable alternative for the winged chisel.•The forward bent blade had a better performance than the backward type in soil loosening.•The MWD was significantly less for all bent blades than that for the winged chisel.•The dual-bent blades had significantly higher soil disturbed cross-sectional area. Irrigated and dryland crop production under conservation tillage systems have been increasing in Iran in recent years. However, due to unstable and hardsetting soil structure, choosing suitable implements for effective soil loosening is still under investigation. In this study, forward and backward double-bent blade subsurface tillage implements with two rake (7.5° and 15°) and bend angles (10° and 20°) were developed and their soil loosening performance under surface tillage (15cm deep) was compared with a commercially-available winged chisel plow under two water contents (0.7 and 0.9 plastic limit) in a clay loam soil at the Research Field of Isfahan University of Technology (central Iran). The effect of double-bent blade implement angles on soil disturbance area, percent of residues remaining on soil surface, clod mean weight diameter (MWD), and soil bulk density was investigated using a split plot experiments in a randomized complete block design. In dual-bent blade implement, the soil main rupture planes were initiated from side edges of the blades and intercepted the soil surface laterally, and it acted as a wide tine; whereas for a winged chisel, the rupture planes initiated from the front edges, and it acted as a narrow tine. The dual bent blades had significantly higher soil disturbance area than the winged chisel. The largest disturbed area was obtained when the forward bent blade was used with a rake angle of 15° and a bend angle of 10°. The smallest MWD was obtained when the forward bent blade was used with a bend angle of 10° and a rake angle of 7.5°. The MWD of dual bent blades was significantly smaller than the winged chisel plow. Soil water content had a significant effect on both MWD and the residue remaining on the soil surface when the soil was chisel plowed; however no significant effect was observed when the soil was plowed with the dual-bent blade implements. The amount of residue remaining on the soil surface after plowing with the winged chisel was significantly less than the case when the dual bent blades were used. A forward dual-bent blade with a rake angle of 7.5° and a bend angle of 1