Pasture restoration with native perennial grass species

Jessica Jury

Bauxite strip-mining at Boddington Bauxite mine conducted by South32 currently occurs on both state forest and private land. All sites are to be rehabilitated to their previous land use purpose, state forest, agricultural use or as agreed with private landowners. Previously, the rehabilitation of pasture has been unsuccessful, resulting in early senescence, low productivity and non-persistent pasture. A review of studies conducted on privately owned properties at Boddington concluded that poor pasture growth on rehabilitated land post-mining was due to shallow topsoil depth; low portion of fine particulates in the profile; high gravel content; poor soil handling methods; and the removal of the duricrust layer. Based on these factors, a glasshouse trial was conducted to determine if the addition of a duricrust layer or clay layer improved annual pasture sustainability, but it was determined that the duricrust layer did not function as previously suggested. This study attempted to repeat the glasshouse trial with native perennial grass species, Austrostipa elegantissima, Rytidosperma caespitosum and Microlaena stipoides. The sustainability and suitability of the species for pasture were determined through dry biomass weight and nutrient analysis of the native perennial grass species relative to the currently used introduced annual, Trifolium subterraneum. A second study was conducted to determine the cause of the high death rate that occurred in the first 6 weeks of experiment 1’s glasshouse trials. The results from Experiment 1 suggest that T. subterraneum suffered from a potassium deficiency, and the native perennial grass species were suffering from phosphorus and nitrogen deficiency (P = 0.1%; total N = < 2%). Experiment 2 results suggest that the survival of seedlings was negatively affected by the application of fertiliser, with the no-fertiliser treatment having the highest survival, and the over-application rate having a significantly lower survival rate (p-value <0.001). In conclusion, the fertiliser regime currently used at Boddington Bauxite mine is unsuitable for supporting and facilitating perennial pastures on rehabilitated soil profiles.

Pasture restoration with native perennial grass species

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