Soil erosion is a significant environmental issue throughout the Hunter Valley.
Low soil fertility, salinity, sodicity (high levels of sodium) and poor soil structure mean that these soils are inherently prone to degradation, leading to loss of topsoil and the formation of erosion gullies.
These same soil characteristics make revegetation of gully erosion difficult. The establishment of ground cover on rehabilitated erosion gullies can take years and in many cases the bare, exposed subsoil will never achieve good groundcover.
Correction of soil deficiencies usually involves the application of chemical ameliorants such as lime to treat soil acidity, gypsum to treat sodicity (high levels of sodium) and improve soil structure, and nitrogen and phosphorous fertiliser to boost growth.
However organic matter is also usually deficient. Research has shown that recycled organic matter (compost) has a greater influence on repairing soil structure than lime or gypsum and it is now considered to be a key ameliorant for long term successful revegetation of major erosion gullies.
As part of its program of market development research for recycled organics, the NSW Department of Environment, Climate Change and Water (DECCW) has invested significant funds over the past five years into trialling recycled organics applications in the Hunter and other regions.
Using DECCW Best Management Practice Guidelines, the Hunter-Central Rivers Catchment Management Authority (CMA) has used recycled organic matter to revegetate large erosion gullies in a variety of landscapes in the Hunter Valley and has contributed to improvements in the efficient application of organic products.
Sites were treated with one application prior to sowing with ground covers using the following criteria:
- Optimum depth for batters (approx 3:1) 25mm – 30mm
- Material (60/40 blended composted soil conditioner and coarse mulch)
- Optimum depth for flat areas having water diverted away from site 25mm
- Soil conditioner material used on flat areas.
On past projects a 60/40 blend was used, however on the Liddell site a 50/50 blend of soil conditioner/coarse mulch on the batters, and soil conditioner on the floor of the shaped gully area was trialled.
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