20210317 08582900 1.0 TRUE Soil Depth to Hard Soil/Gravel/Rock Soil depth (Webb & Lilburne 2011) is defined according to a traditional agronomic concept of soil depth (Taylor & Pohlen 1970). In a practical sense, it can be thought of as the depth to a layer that makes augering or digging difficult. Soil depth is identified as the depth to: Landcare Research