Effects of agricultural management on tenosols in northern Tasmania

Attributes of 15 Tasmanian sandy tenosols were assessed using field and laboratory techniques to determine differences under 3 typical forms of agricultural management: long-term pasture, cropping with shallow tillage using discs and tines, and cropping (including potatoes) with more rigorous and deeper tillage including deep ripping and powered implements. Soil organic carbon in the surface 75 mm was 2.6% under long-term pasture compared with 1.1% in rigorously tilled cropping paddocks. Readily oxidisable carbon concentrations were 2.3 mg/g and 1.0 mg/g, respectively. These differences were negatively correlated with the number of years cropped, which we viewed with concern. Infiltration rate was greater and shear strength less in cropped paddocks compared with long-term pasture. Dry bulk density was greater and total porosity and macroporosity were less in rigorously tilled paddocks. Subsoil compaction was apparent in paddocks which had grown potatoes. Cropping was not clearly associated with smaller or less stable aggregates. A survey of farmers' perceptions found that they identified more healthy than unhealthy soil attributes under all management histories. Significant negative correlations were found between the number of unhealthy attributes identified in a farmer survey and laboratory-determined water-stable aggregates and mean weight diameter of dry soil aggregates. The effects of cropping are not associated with a broad range of degraded soil attributes on these Tasmanian tenosols.