James Hall 1
1Juliet Creek Consulting Pty Ltd
Peer Review: Chris McDonough
Key Words: Mallee seeps, soaks, dune seeps
- Water that drains beyond the crop root zone in sandy soils can be lost to ‘deep’ drainage, or, can form ‘perched’ watertables in areas where restrictive layers limit downward water movement.
- The movement or ‘seepage’ of perched water along restrictive layers can cause development of perennial waterlogging or ‘seeps’ at ‘discharge’ sites (see Figure 1) – resulting in the loss to production of some of the best mallee soils.
- Evidence suggests that productive land lost to perennial waterlogging (‘seeps’) is increasing across the SA Murray Mallee.
- Investigations at three subcatchments in the SA Murray Mallee have shown that the restrictive layer upon which perched watertables and seeps form is ‘Blanchetown Clay’ (see Hall et al. 2009).
- The formation of seeps is only a symptom of a much wider sub-optimal water use and productivity issue on sandy soils in the Murray Mallee – presenting opportunities for better water use and productivity.
Funding for this and associated work has been provided by Natural Resources SA Murray-Darling Basin/DEWNR, the National Landcare Program (NLP), Grains Research & Development Corporation (GRDC), Mallee Sustainable Farming (MSF) and the Loxton Research Centre (PIRSA). Cooperation, assistance and sourcing of funding is also acknowledged from Bernadette Lawson (NR SAMDB), Tim Herrmann (DEWNR), Chris Henschke (hydrology / PIRSA), Simon Knowles (drilling / Earthwise Services), Chris McDonough (farmer engagement, agronomy, trial work and monitoring / Insight Extension for Agriculture), Brian Hughes (soil science / PIRSA) and, especially, the cooperating farmers. This work came to an unexpected halt with Natural Resources SAMDB having reduced funding levels and a shift in priorities. Some monitoring work is still on-going.