Effect of subsoiling on soil physical properties and pasture production on a Pallic Soil in Southland, New Zealand

This three-year study examined the effects on soil physical properties and ryegrass-white clover pasture production of subsoiling in a Pukemutu silt foam (Pallic Soil). A range of soil physical properties were measured in 6-cm incremental depths to 30 cm. Subsoiling loosened the topsoil by pulling conventional tines and winged tines, 50 cm apart through the soil at a depth of 25-30 cm. Subsoiling increased macroporosity by up to 27% of the soil volume, and increased saturated hydraulic conductivity and air permeability by up to two orders of magnitude. Improvements in soil physical conditions were evident up to 2.5 years after subsoiling at 18-24 cm, although recompaction and settling had occurred in the upper 18 cm of the soil profile. For the majority of the trial, there was no significant improvement in pasture production in subsoiled treatments. Pasture dry matter was significantly reduced (by 39%) during a dry summer period following winged subsoiling, mainly due to moisture stress.