Tillage recommendation for commercial forest production: Should tillage be based on soil penetrability, bulk density or more complex, integrative properties?

Abstract Efficient soil tillage methods to create a favorable environment for commercial forest require proper evaluation of soil compaction with depth, by using operative indicators of physical quality for diverse soils. Our aim was to investigate the spatial variability of field-measured penetration resistance (PR), and then determine the relationships between penetrability and mechanical and hydrologic properties of Planosol, Nitisol, and Regosol used for eucalyptus production. Low, intermediate, and high compaction states were defined based on field PR spatial variability, and in those areas with distinct compaction states we determined bulk density, degree-of-compactness, macroporosity, water retention and availability, and least limiting water range. The soil compaction states are related to composition or capacity (mass/volume) properties, most consistently with soil bulk density and relative compaction. Whether using simple measurements such as penetrability and bulk density, or more complex, integrative properties (e.g. degree-of-compactness and least limiting water range), tillage recommendation would be the same. Namely, deep tillage for Nitisol, and shallower tillage for Planosol and Regosol. In practical terms, the first soil requires deep subsoiling, and second and third soil demand shallower subsoiling associated or not with ridging. In conclusion, mapping of soil compaction states based on PR data can be used for best management practices and tillage recommendation for forest installation.