High quality pastures, areas established with native trees and areas established to native pastures, featured at a recent Upper Hunter Mining Dialogue Pasture Restoration Field Day.
During the day, rehabilitation efforts at two mines were highlighted.
There was Glencore's Liddell coal mine, under the guidance of environment and community manager Ben de Somer, along with Bloomfield's Rix's Creek operation, led by environmental group manager Chris Knight.
Tropical grass combined with legumes, like white clover and annual species, were impressive and via independent studies have proven they are able to carry far higher beef productivity per hectare than adjoining, relatively unimproved, native pastures.
Once coal mining ends, re-establishing these often large areas to a combination of agriculture and native habitat is typical for a mining company, as well as regulatory requirement.
The field day attendees learnt pastures can be established, with care and sound knowledge, to high quality grazing land when mining ended.
Research details tropical grass pastures on these areas, that is also occurring in adjoining farms, can be far more productive and profitable than native grass pastures.
Pastures based on selected tropical perennial grasses, plus winter legumes, combined with soil deficiencies like phosphorus correction, are vital parts of the mines' pasture development.
Local research on rehabilitation sites has shown soil deficiencies like phosphorus are little different to that on adjoining farmland grazing areas.
Sulphur is also sometimes marginal. Detailed animal testing and soil analysis has shown no abnormal toxicities have occurred in these soils or animals post mining days.
Restoration of mined areas aims to mimic pre-mining landscapes as well as restore them to quality agriculture.
For example, topsoil - which is generally far more nutrient rich than sub soils - is set aside in early mining stages and returned as a surface layer.
Pasture studies, conducted by consultant Neil Nelson and agronomists from NSW Department of Primary Industries (Neil Griffiths and colleagues) included perennial grasses selected for persistence and productivity.
The best species vary according to rainfall, soil type and land aspect.
The main ones include rhodes grass, kikuyu, setaria, bambatsi and gatton panic.
Premier digit grass from current and other research indicates a likely large role in future establishments while it is also doing well in recent ones.
A range of legumes are successfully used in the rehab pastures.
These include medic, woolly pod vetch, sub clover, white clover, arrowleaf clover and, possibly for future inclusion, biserrula, rose clover and for acid soil areas serradella.
Rhizobia application is a key area to ensure legume success and their ability to build nitrogen for grass quality and quantity.
Adding appropriate rhizobia strains for each species via Alosca granules is the most reliable way to ensure rhizobia survival - especially if sowing dry.
Particularly noteworthy are soil fertility correction programs which are essential for good plant growth and animal performance.
Sound use has been made of organic products such as bio solids, recycled green waste, and gypsum.
Single superphosphate is also used to correct phosphorus and sulphur deficiency as well as urea for nitrogen where appropriate.
Grazing management is a difficult aspect in newly-developing areas as ideal management generally requires added fencing, laneways and water points.
More paddocks help with grazing and resting periods which is important for grass survival and coexistence with legumes.
In post-mine areas, this phase is commonly delayed. However, good progress is occurring.
In most environments, weeds can be an issue in pasture development.
However, as commonly experienced on farmland, established post-mine tropical pastures appear to be outcompeting these problems.
James Barben, Upper Hunter Mining Dialogue secretariat, well summarised the field day.
"It was great to host such a broad range of stakeholders [including farmers and farmer representatives] showing that productive and sustainable grazing, based on tropical grasses and winter legumes, including via soil deficiency correction, can be achieved post-mining," he said.
Next week: Improving pasture legume content highest farmer priority.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact 0428 752 149.
