Chemical and physical amelioration of subsoils has limited production benefits for perennial pastures in two contrasting soils

• Chemical and physical subsoil conditions may limit perennial pasture production.
• Contrasting soils were modified with fertiliser, lime and organic matter.
• Soils were softer, less acidic with increased nutrient availability.
• There were no consistent gains in productivity compared to surface applications.

While broad acre grazing is the major agricultural land use in Southern Australia, there has been comparatively little research on the effect of alleviating subsoil limitations on pasture production under field conditions. The effect of modifying the physical and chemical properties of soil on perennial pasture production and root distribution was studied on 2 major soil types in two regions of Southern Victoria, Australia. Soil treatments included the deep placement of fertilisers, lime and organic matter, and soil disturbance to a range of depths. The Ellinbank field site on a Ferrasol was monitored for 2 years, while the Curdievale site on a Sodosol was monitored for 1 year. There were substantial changes in soil physical and chemical characteristics as a result of the soil treatment. Soils were softer, less acidic and had increased nutrient availability within the profile. However, these changes did not result in consistent gains in pasture productivity, over-and-above the normal practice of surface applied nutrients and lime. The deep placement of organic matter at the Ellinbank site resulted in an initial increase in pasture production, but this effect declined with time. The perennial ryegrass (Lolium perenne L.) based pasture was shallow-rooted and substantial modifications to the soil profile did not result in significant changes to root distribution. It appears that the productivity of perennial ryegrass pasture in high rainfall regions can be maintained at a productive level, with a localised nutrient and water supply.