Assessment of an innovative soil aerator on soil physical disturbance and reducing runoff on compacted grassland

Poor grassland management practices increases compaction and reduces infiltration leading to increasing risk of poaching and runoff generation. On-site impacts of grassland compaction include the loss of topsoil structure which also reduces soil ecosystem functioning. In addition, ongoing diffuse water pollution from compacted grassland limits the ability of the UK’s authorities to meet EU water quality guidelines such as the Water Framework Directive and address flood risks in areas of extensive grassland management (e.g. Boscastle, 2004). This study investigates the effects of an innovative ground-driven rotary soil aerator at alleviating soil compaction and reducing overland flow (designed by Mr. Roger Clay, Herefordshire). The magnitude of soil disturbance from slotting was assessed at the Cranfield University Soil Dynamics Test Centre soil-bin. Draught and vertical force requirements and tillage efficiency were also determined for varying depth and horizontal and vertical angle combinations using an Extended Octagonal-Ring Transducer (EORT). The effect of various slotting treatments on runoff was then investigated on a steep compacted permanent pasture in Herefordshire using erosion plots and simulated rainfall. From the soil-bin assessment, soil disturbance was most efficient (lowest specific draught) at 100 mm depth, a vertical angle of 18° and with increasing horizontal angle (0° to 10°). The draught requirement for a single bladed disc at 18° vertical ranged from 0.88 to 1.24 kN (90-126 kg force) and a maximum vertical force or ballast requirement of 257 kg force per bladed disc. Slotting treatments reduced runoff by 75% as compared with the non-slotted control.