SOIL IMPROVEMENT: Victor Harbor farmer Alister Carmichael says clay spreading, and now delving, is the cheapest way he and his family can improve their farm without buying more land and (inset) the delving machine at work.HAVING experienced good results from clay spreading his unproductive, non-wetting sands, Waitpinga farmer Alister Carmichael has this year turned to clay delving as another method of improving production.
The 1090-hectare Carmichael property Santa Cruz, located seven kilometres west of Victor Harbor, runs mainly livestock with a small amount of cropping.
“The end result we want is better pastures,” Alister said. “Clay spreading, and now delving, we think is the cheapest way we can improve our farm without buying more land.”
Alister says that about five years ago he started inquiring about clay spreading and delving on the Fleurieu Peninsula through the local natural resource management board and Rural Solutions SA.
“I was finding that not much had been done locally about clay spreading or delving, and any machinery was based either on Eyre Peninsula or in the South East where they had been doing it for a long time.”
As a result, the Glacier Soils Group formed and trialled small areas of clay delving and clay spreading with funding from the National Landcare Program. Further projects, funded by Caring for Our Country and Woolworths, have provided technical support and offset some of the costs associated with clay spreading and delving and overcoming the difficulty of getting machinery to the area.
“We were finding that contractors were reluctant to travel to the area for less than 12 hectares, so working as a group has been of benefit,” Alister said. “The incentive payments through the project have also made it easier for us in terms of funding.”
Since then, Alister has clay spread about 35 hectares a year (175ha total), and is very pleased with the results. He has observed better and more even germination, better efficacy of chemicals as everything is germinating at the same time, and better fertility.
“We began in our worst paddocks and we’re starting to see each paddock that we’ve done getting a little better each year,” he said. “This year is the first year we’ve tried delving on a broader scale, so we’re keen to see what the difference is.”
The practice of delving involves ripping up subsoil clay lying one metre or less beneath sandy topsoil. An implement fitted with large ‘ripper’ tynes is used to break into the clay pan and bring clods to the surface. Clay is allowed to dry before being broken up and incorporated into the topsoil with normal tillage operations.
Alister says that using a delving contractor they completed 35ha one week ago. His initial assessment of the two methods is that while delving is cheaper, the incorporation of the clay is harder.
“We’re expecting that incorporation will take longer as the delving has left the surface a lot rougher,” Alister said. “But at the same time, delving has allowed us to break up the subsoil clay and hence get better root growth and mix up the soil profile as well.”
*Full report in Stock Journal, January 27, 2011.
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