PONDING has been shown to have the lowest up-front costs for reclaiming clay pans but it seems the jury is still out on possible quicker responses from both blade ploughing and cross-ripping.
The three methods were the focus of the Claypan Rehabilitation and Soil Health Workshop in Charleville which was an International Year of the Soil event hosted by the South West NRM recently.
The workshop included an overview of rehabilitation methods and a presentation on soil health from soil scientist Dr John Bennett from the University of Southern Queensland. Participants also visited Brock and Katrina Hindmarch’s property Wallal about 22km south of Charleville to see the trial work first-hand.
Despite the ongoing extreme drought conditions, ponding was shown to have had the best response to the very limited rainfall received in 2015.
South West NRM Landcare project officer Jed Sommerfield said the trial was established to provide insights into rehabilitating clay pans with Mitchell grass pasture.
Mr Sommerfield said clay pans were formed when the top soil was eroded exposing clay subsoils. The loss of the top soil could be caused by a combination of factors including overgrazing for periods of 40-60 years, the total grazing pressure including kangaroos, and wind, water and impact erosion.
“Ponding showed the best response to the very limited amount of rain,” Mr Sommerfield said. “After 10-14 days there was still a soft enough crust on the ponded area to allow gidyea burr and other pioneer species to germinate.”
However, there was no response from the areas that had been either blade ploughed or cross-ripped because there had been insufficient rainfall.
Mr Sommerfield said the downside of ponding was that as a rehabilitation system it could take decades to restore degraded country.
“In this case ponding showed that with a little bit of rain a response was still achieved,” he said.
“What we are keen to understand now is how the three different rehabilitation methods would respond with different rainfall events.”
AT $26.34/hectare ($10.66/acre) ponding proved the cheapest method of rehabilitating clay pans. While far cheaper than the $141.32/ha ($57.19/acre) for cross-ripping or $205.42/ha ($83.13/acre) for blade ploughing, it can take decades for ponding to achieve its objective. Mechanical disturbance of the soil could prove faster and cheaper in the long run.
Mr Sommerfield said the costs were based on standard rates charged by contractors..
“While it was rightly assumed that blade ploughing would be the most expensive we were surprised at the final cost of cross-ripping,” Mr Sommerfield said.
“It may be that a single pass with the rippers would not only be cheaper but also possibly a better option for capturing rainfall.”
The Claypan Rehabilitation and Soil Health Workshop was jointly sponsored by the University of Southern Queensland, Soil Society of Australia, the Regional Collective Groups, South West NRM, and Queensland Country Life.
For more information see the Mulga Graze Handout handbook at www.southwestnrm.org.au
