Department of Agriculture and Food, 20 Gregory St, Geraldton 6530, email@example.com
Subsoil compaction induced by machinery traffic reduces root growth, rooting depth and limits access to moisture and nutrients. Around 70% of soils in the Western Australian wheatbelt have a moderate to high risk of subsoil compaction. Deep ripping with tined implements is the most common way growers rectify subsoil compaction. A deep ripper was specifically constructed to investigate ripping below 450 mm and used in eight trials, at six sites across WA. The ripper has shallow leading tines ripping to 300 mm and rear trailing tines with capacity to rip to 600 mm. Unique to this ripper were topsoil slotting plates attached to the rear tines. A pair of trailing plates, separated by 130 mm, opens a slot in the soil as the tine moves through. A volume of topsoil then falls into the gap created by the plates that are trailing below the soil surface. Results over two years indicate that topsoil slotting plates add to the yield response from deep ripping and provide at least two years of continued positive response in a range of soil types. In 2016 topsoil slotting plates resulted in a 39% yield response, when compared to nil ripping, on grey clay with sodicity at depth. This soil often responds negatively to deep ripping. Further positive responses include 53%, 45% and 17% on loamy yellow sand, sand over gravel duplex and calcareous loamy earth respectively.